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Performance Evaluation of WTP at Gadchiroli

INTRODUCTION

1.1 General

Safe drinking water is a basic need of all humans. To protect the human health, community

water supply must be reliable, adequate of assured quality and readily accessible to all segments

of the consumers. In India as well as in many countries, the expected level of progress in

providing one of the most basic services to the people viz. safe and affordable drinking water and

sanitation have not yet been achieved. The current practices of water purification are seldom

adequate to produce secured water supply. It is essential to develop various tools to improve

water purification and distribution system to achieve the goal of providing safe drinking water.

A very large demand of civic amenities which have to keep with increasing demand of rising

population. Therefore, identification of source of water supply its conservation and optimum

utilization is of almost importance. Even the present scale of water supply to urban and rural

population is grossly inadequate and not all communities are provided with safe water supply. In

old day, population was very thin and also in the absence of industrial and agricultural

development, a little amount of waste used to be disposed in water bodies. Water resources have

maintained quality of natural self-cleaning mechanism. Today the human activity causes

pollution and contamination of river and lake water, sea water, ground water and even treated

piped drinking water, which is challengeable.

The objective of present study was to evaluate the performance of the water treatment Plant

at Gadchiroli District to focus the attention operation and maintenance agency of plant on gaps

and deficiencies in operation and maintenance, if any and to suggest practical measure for

possible improvement. To implement performance assessment, it is necessary to develop

adequate and representative performance indicators. Good performance indicators can specify

the measurable evidence that is necessary to document the achievement of a goal. To provide the

higher quality and stable water to the customers, the water utilities themselves should establishthe proper maintenance and management programs to enhance the availability of plant facilities

and equipments in the water treatment plant. The aim of this research work is to set up the

performance evaluation system for the Gadchiroli water treatment plant.

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1.2 Water Supply Development in India

The development of public water supply in India actually belongs to the post-

independence era prior to independence, the progress in the fields of urban and rural water

supply was sporadic and slow and depended on the needs and priorites of the alien rulers. After

independence, an extensive programme was embarked upon to meet the necessity of providing

the bare requirements water in the rural areas. The Environmental Hygience Committee

appointed by the Union Govt. providing water supply and sanitation facilities for 90 percent of

our population within a span of 40 years. The National Water Supply and Sanitation Programme

was formally launched by the Govt. in 1954. Under the programme, long-term interest loans for

Urban Water Supply Schemes were sanctioned. For rural schemes Central and state

Governments grant-in-aid was made upto 75 percent of the cost of schemes, the balance to be

made by beneficiaries.

Inverstments in public water supply and sewerage schemes have steadily increased with

each plan period. Beginning with the First Five Year Plan (1951-56), when a total provision of

Rs. 12 crores for outlay in the Fourth Plan (1969-70) increased to Rs. 409 crores of which Rs.

125 crores were earmarked for rural water supply schemes alone.

However, it has to be pointed out that in spite of the increasing rate of provisions on thenational urban and rural water supply and sanitation programmers, we have up till now been able

to provide safe water supply to 5 percent of our villages and water supply with water-borne

sewerage system to 30 percent of urban population. This shows that the quantum of efforts and

investments made on these programmers are inadequate and we need to considerably accelerate

the pace of the development of our public health engineering programmers in order to provide

the entire community with means of protected or safe water supply and sanitation.

1.3 Status of Water treatment plants in India

India accounts for 2.45% of land area and 4% of water resources of the world but

represents 16% of the world population. With the present population growth-rate (1.9 per cent

per year), the population is expected to cross the 1.5 billion mark by 2050. The Planning

Commission, Government of India has estimated the water demand increase from 710 BCM

(Billion Cubic Meters) in 2010 to almost 1180 BCM in 2050 with domestic and industrial water

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consumption expected to increase almost 2.5 times. The trend of urbanization in India is exerting

stress on civic authorities to provide basic requirement such as safe drinking water, sanitation

and infrastructure.

The rapid growth of population has exerted the portable water demand, which requires

exploration of raw water sources, developing treatment and distribution systems. The raw water

quality available in India varies significantly, resulting in modifications to the conventional

water treatment scheme consisting of aeration, chemical coagulation, flocculation,

sedimentation, filtration and disinfection. The backwash water and sludge generation from water

treatment plants are of environment concern in terms of disposal. Therefore, optimization of

chemical dosing and filter runs carries importance to reduce the rejects from the water treatment

plants. Also there is a need to study the water treatment plants for their operational status and to

explore the best feasible mechanism to ensure proper drinking water production with least

possible rejects and its management. With this backdrop, the Central Pollution Control Board

(CPCB), studied water treatment plants located across the country, for prevailing raw water

quality, water treatment technologies, operational practices, chemical consumption and rejects

management.

The collected information was processed & broad observations on various treatment

plants are as follows.

At many water treatment plants, the raw water is very clean having turbidity less than 10

NTU during non-monsoon period. Whenever the turbidity is so low, alum or Poly Aluminium

Chloride (PAC) is not added, although the water passes through all the units such as flocculators

and settling tanks before passing through rapid sand filters.

Alum is being added as coagulant in almost all Water Treatment Plants, however,

recently water treatment plant at Nasik and Pune have started using PAC instead of alum, which

is in liquid form. The water treatment plant personal appeared to prefer PAC as no solution is to

be prepared, as in case of alum. Bhandup water treatment complex, Mumbai is using aluminium

ferric sulphate, which is one of the biggest water treatment plant in India.

In few plants, non mechanical devices such as hydraulic jumps are being used for mixing

of chemicals. Also, paddles of flash mixer were non functional in some water treatment plants.

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Some of the water treatment plants are using bleaching powder for chlorination, while

majority are using liquid chlorine. The operation and maintenance of chlorinator was far from

satisfactory and chlorine dosing is often on approximation. Instrumentation part in terms of

chemical addition and chlorination appeared to be imperfect in most of the plants.

Some water treatment plants were using alum bricks directly instead of making alum

solution before addition.

In few plants, tapered flocculation units with flocculator of varying speeds are in use. In

this case the settling tanks are rectangular with hopper bottom. These tanks do not have

mechanical scraping arrangement and are cleaned during the period of filter backwash.

Pre-chlorination dose, in case of Agra water treatment plant was reported to be high as 60

mg/l, which is a matter of great concern for water treatment plant authorities. This is because rawwater BOD is very high due to discharge of industrial effluents on the upstream side of water

treatment plant intake.

All the water treatment plants (except defluoridation plants) have rapid sand filters. In

addition to rapid sand filters, slow sand filters were in operation at Aish Bagh, Lucknow and

Dhalli, Shimla. At Nasik, water treatment plant had dual media filter using coconut shell as

second medium, which is being replaced by sand.

Filter runs are generally longer about 36 to 48 Hrs. during non-monsoon period except

Sikandara WTP, Agra where filter runs are shorter during this period due to algae problem all

though rapid sand filters are located in a filter house. This is due to high pollution (BOD) of raw

water. Normally, wherever rapid sand filters are located in filter house, algae problem is not

encountered. Some of water treatment plants, where rapid sand filters are in open, algae problem

is overcome by regular cleaning of filter walls or pre-chlorination.

Mostly, filter backwash waters & sludge from water treatment plants are being

discharged into nearby drains, which ultimately meet the water source on downstream side of

intake. However, exception is at Sikandara water treatment plants, Agra, where sludge and filter

back wash waters are discharged on upstream side of water intake in Yamuna River.

In some of the water treatment plants, clarifiers are cleaned once in a year and the sludge

are disposed off on nearby open lands. AT Haiderpur Water Works in Delhi, reuse of sludge and

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filter back wash water is under consideration. In case of Dew Dharam water treatment plant at

Indore and Narayangiri water treatment plant at Bhopal, the backwash water is being sused for

gardening, while at Balaganj water treatment plant, Lucknow, filter backwash water is recycled

by way of sedimentation and feeding them at inlet of water treatment plant.

In many cases, details of water treatment plant units such as their sizes, specifications,

layout etc are not available. This is possibly because of water treatment plant executing agency

and water supply system operation & maintenance agency are different. Water treatment plant

operation manual were also not available at many plants.

In most of the cases, adequacy of water treatment from health point of view is ensured by

maintaining residual chlorine of 0.2 to 0.1 mg/l at the farthest point of distribution system. Very

few water treatment plants have facilities for MPN testing.

Water treatment plants are either operated or maintained by Public Health Engineering

Departments or local municipal corporations. At Shimla, water treatment plant is under Irrigation

and Public Health (IPH) of the Himachal State Government, whereas water distribution is looked

after by Shimla Municipal Corporation.

Operation and maintenance of Sikandara, Agra Red Hills, Chennai, Peddapur,

Hyderabad, Kotarpur, Ahmedabad etc. water treatment plants have been assigned to the privateorganizations. In Uttar Pradesh, execution of water treatment plant is carried out by UP Jal

Nigam and operation & maintenance is carried out by UP Jal Sansthan, not by local

municipalities.

Okhla water works, Delhi gets raw water from rainy well and is subjected to ozonation

and denitrification. Operation and maintenance of ozonators and denitrification plant is being

looked after by a private organization. It has been learned that ozonation is being carried out

principally for iron removal and not for disinfection.

Typical problem of excess manganese is faced at Kolar water treatment plant, Bhopal

during May to October. This problem is being tackled by adding KMNO4 and lime at the inlet.

In Surat, at Katargam water works, raw water is coloured. The treatment plant is having proper O

& M, could remove colour.

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Mundali water treatment plant at Bhubaneswar has a capacity to treat 115 MLD, but in

practical operated for 1 shift to treat 40 MLD water. Whereas, Palasuni water works at

Bhubaneshwar is having capacity of 81.8 MLD, but plants are overloaded to a total of 106.5

MLD.

Kotarpur water treatment plant located at Ahmedabad has a capacity of 600 MLD, but

treating only 300 MLD, due to shortage of raw water.

State of art water treatment plant exists at T.K. Halli, Bangalore, which has all the

operation computerized. This plant has pulsator type clarifiers and plant authorities appeared to

be worried about excess chemical consumption and dilute sludge from these clarifiers. At this

plant, clarifier sludge is being conditioned with polyelectrolyte and dewatered by vacuum filters.

Filter backwash waters are discharged into the nearby drain. The distance of Water treatment

plant is more than 80 kms from Bangalore city. Looking at the distance, it may be appropriate to

have chlorination facility near to the city and near the point from where distribution starts.

1.4 Status of Water Supply in Maharashtra State

As per the constitution of India, taking care of the water supply and sanitation needs of

the citizens is a responsibility of State Governments and its of governance such as the Zilla

Parishad, Urban Local bodies and to some extent the Gram Panchayats also. In Maharashtra, the

Ministry of Water Supply and Sanitation along with the department of Water Supply and

Sanitation was created in 1996 to exclusively concentrate on the poor coverage and access to

these essential services in both urban and rural areas. The Ministry is responsible for setting the

policies for the State in this sector and coordinate with the Central Government and other key

institutions.

The Ministry is headed by the Minister of Water Supply and Sanitation and is supported

by the State Minister for Water Supply and Sanitation. The Secretary heads the Water Supply

and Sanitation Department (WSSD).

It is planned to allocate funding of Rs. 438 Crore to be spend in next four years to

achieve goals related to providing safe drinking water to the community. The rural water supply

scheme in the state has been planned considering growth of about 2.5% in state population.

(Present population of Maharashtra in about 9.6 crore)

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The Minister of Urban Affairs of the Government of India, formed in 1985, was set up to

review State development plans, and influences the policies and practices of the Urban Water

Supply and sewarege Sector. The Planning Commission also has a special cell that advises on the

sector policy.

Central water Commission conducts hydrological observations in Wainganga basin at 21

Stations. These sites are maintained under Key Hydrological Stations. Out of these 21 sites,

water quality is monitored at 9 sites. Central Water Commission has been monitoring the water

quality of Wainganga river for more than 30 years. The various water quality parameters such as

Physical, Chemical, Bacteriological, Trace & Toxic metals and Pesticides are observed at these

sites. The data for core parameters viz. pH, Electrical Conductivity (EC), Biochemical Oxygen

Demand (BOD), Dissolve oxygen (DO), Nitrate (NO3-), Nitrite (NO2

-), Total Coliform (Tcol)

and Faecal Coliform (Fcol) are considered for the year 2005-06 to 2009-10 at these nine

locations in the basin to study the water qualityboard.

1.5 WATER TREATMENT TECHNOLOGIES

Three basic purpose of Water Treatment Plant are as follows

I. To produce water that is safe for human consumption

II. To produce water that is appealing to the consumer

III. To produce water - using facilities which can be constructed and operated at a reasonable

cost.

Production of biologically and chemically safe water is the primary goal in the design of

water treatment plants; anything less is unacceptable. A properly designed plant is not only a

requirement to guarantee safe drinking water, but also skillful and alert plant operation and

attention to the sanitary requirements of the source of supply and the distribution system are

equally important. The second basic objective of water treatment is the production of water that

is appealing to the consumer. Ideally, appealing water is one that is clear and colorless, pleasantto the taste, odorless, and cool. It is none staining, neither corrosive nor scale forming, and

reasonably soft.

The consumer is principally interested in the quality of water delivered at the tap, not the

quality at the treatment plant. Therefore, water utility operations should be such that quality is

not impaired during transmission, storage and distribution to the consumer. Storage and

distribution system should be designed and operated to prevent biological growths, corrosion,

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and contamination by cross-connections. In the design and operation of both treatment plant and

distribution system, the control point for the determination of water quality should be the

customers tap.

The third basic objective of water treatment is that water treatment may be accomplished

using facilities with reasonable capital and operating costs. Various alternatives in plant design

should be evaluated for production of cost effective quality water. Alternative plant designs

developed should be based upon sound engineering principles and flexible to future conditions,

emergency situations, operating personnel capabilities and future expansion.

1.6 Water treatment Plant at Gadchiroli

The city of Gadchiroli located in the border of Maharastra & Chhattisgad State. Present

population of Gadchiroli city is 53,800. Water supply to the city is being arranged fromWainganga river (Bormada Ghat). The capacity of Water treatment plant is 12.5 MLD, which is

double to required for present population.

The Water treatment plant scheme was sanctioned in 1996 to 1997. The water treatment

plant was constructed in the year 10/8/2003. The source of water is Bormada Ghat of Wainganga

river which is at 3 km from 0 mile stone of the Gadchiroli city. The Wainganga river is having

250 meter wide basin. All water supply to the Gadchiroli city is being catered by this plant. The

plant is running for 8+8=16 Hours into two shifts. Though the plant is designed for 12.5 MLD

but only 6 MLD of water is being treated & supplied to the city.

The design and construction of the plant is conventional one the various units being aeration

fountain, flash mixer, clariflucculators, rapid sand filters, chemical house, Clear water sump and

pump house.

1.7 Scope of Work

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Performance of the water treatment plant is an essential parameter to be monitored and

evaluated to better understanding of design and operating difficulties in water treatment plants.

The conclusions of these evaluations may determine required recommendations and highlight

modifications requirements for continuous design and operation scheme.

It was decided to evaluate the performance of the plant at Gadchiroli . The work includes

measurement of pH, Total Solids, Suspended Solids, Residual Chlorides, Turbidity, Flow, D.0 of

water at various stages of treatment, such as inlet and outlet, of cascade aerator, filter and

chlorinated water.

The scope of work comprised mainly the following.

Collection of engineering and design detail of the plant and discussion with plant staff.

Visit to the plant for sampling and analysis with a view to study the characteristics of raw

and treated water and performance of treatment units at various stages of treatment.

Performance Evaluation with respect to operation and maintenance of the plant including

plant safety.

Providing practical recommendation to improve the performance of the water plant.

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Fig. 1.1 Image of Gadchiroli water treatment plant

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LETERATURE REVIEW

2.1 General

From the public health point of view, it is necessary that all water supplies must be

invariably free from all types of impurities whether suspended or dissolved in water and no

untoward risk should occur to the health of the public as a result of any water contamination.

When the surface waters as from rivers or lakes were used, the method employed was to let such

waters remain undisturbed or quiescent for some time till all the turbid suspended particles

settled down and clear potable water drawn off from upper layers. This led to the construction of

impounding reservoirs.

The next development in the purification methods was through the process of Filtration i.e.,allowing water to pass through beds of which could not be removed earlier were caused to be

removed. It was found that the process of filtration was greatly accelerated if waters were

pretreated with certain substances which when added formed large masses of precipitates or flocs

out of the impurities present and which in the process settled down and were ultimately removed.

The water pre-treatment process is now called Coagulation, but this process was equally known

to the ancients who used solutions of certain vegetable called nirmali. Nowadays, alum is

chiefly used for this purpose.

The water having undergone through filtration was still found to contain minutely-sized

living organisms as were apparently not visible to the naked eye. These were later found to be

responsible for breeding germs causing diseases like cholera, typhoid, dysentery etc. In order,

therefore, to thoroughly ensure protected supplies devoid of any health hazard, it was found

necessary to remove these organisms by disinfecting water through the process of adding

chlorine or chlorinous compounds to water i.e., chlorination. Other methods of disinfecting

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investigate water quality. The results drawn in this paper outlines comes with the importance of

accurate engineering design and need for continuous and analysis of each unit performance

regularly.

E.E. Chang , Chiang Peng-Chi, Huang Shu-Mei(2007)

This paper highlights performance evaluation systems for the water production

department in the Taipei Water treatment plant which were developed throughout this

investigation. To achieve high quality and stable water to customer, the water utility themselvesshould be establish the proper maintenance program, to enhance the availability of planned

facilities and equipment. Water production cost and removal efficiency are developed and

analyzed to draw out an implementation plan for optimizing the performance of the Taipei water

treatment plant. In addition, establishing a regular performance evaluation

system to identify potential and existing problems so that correction action

could be immediately taken, developing a sound database program, and

cooperating with the stakeholders for source water protection are the major

tasks that should be implemented to achieve the objectives of safe drinking

water and clean water.

R. S. Dhaneshwar, V. P. Sharma, R. K. Gupta, P. S. Kelkar and R. Paramasivam (1991)

The supply water work with single hand to enhance the problem of supplying adequate quantity

of potable water to the public. This paper highlights the performance of various plant units, the

status of operation and maintenance plant feature with laboratory facilities of overall

management of water at Varanasi, Lucknow, Agra, Kanpur, and Nainital in Uttar Pradesh.

S.B. Parjane, M.G. Sane (2011)

This paper highlights the finding for performance of Grey water treatment plant &

laboratory scale system. The evaluation conducted for three seasons & research work carried out

by reviewing the other treatment plant to assure matching of standards & codes.The results

presented in this study establish the potential applicability of the developed

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methodology. This laboratory scale grey water treatment plant is a combination of

natural and physical operations such as settling with cascaded water flow, aeration,

agitation and filtration, hence called as hybrid treatment process. All the natural

and easily available low cost materialswere used for the treatment process.

S. J. Kardile, S. K. Gajendragadkar (1993)

This paper highlights the evaluation of the performance of water Treatment Plant in

Trimbakeshwar, Nasik during the monsoon of the year 1991. Today most of the surface water

are treated in adequate amount irrespective of drinking water. Mostly in recent years, there are

the awareness of clean drinking water in small towns & villages. Actually most of conventional

facilities has limitations, thats why most of world engineers are trying their best to improve this

condition..

2.2 Theory of Water Treatment Plant

2.2.1 Description of Gadchiroli W.T.P.

The Gadchiroli Water Treatment Plant is located just adjacent to Bormada Village on

west side of Gachiroli City. This plant is 3 Km from zero mile stone of Gadchiroli. The

Longitude is 79o

5724 and Latitude is 18o

5706 the plant supply water to Gadchiroli city.The plant is located on an elevation land track at a high level from road and nearby area.

The present capacity of the plant is 12.5 MLD, which can provide water to about 1.5 lakh

peoples, Where as the present population is only 53,800. The plant is constructed in RCC frame

structure in 2001 & commencement of WTP is in 10/8/2003. It was run for 6 month by

Maharashtra Jivan Pradhikaran Department & hand over to the municipal council of Gadchiroli.

The plant includes Intake well, Pump house, Rising main, Stilling chamber, Measuring channel,

Flash mixer, three Clarifloucculator, 4 Rapid sand filter, Chemical house with alum storage

room, chlorine room & water sump etc.

The scheme of WTP at Gadchiroli was sanctioned in 1997. The work of WTP

construction was over in 2002. It is design for 12.5 MLD but working on 6 MLD. The estimated

cost was about 12 cores. The area of land is 5.42 acres. The population was 42,469 in year 2001

& now in year 2011 is 53,800. The design rate of supply is 33.50 LPCD.

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The source of supply is Bormada Ghat of Wainganga river which is perennial in nature &

which is 2 km from Bormada Village. The water from intake to water treatment plant convey

through 560 mm diameter pipe.

Fig.2.1 Layout of water treatment plant of Gadchiroli

2.2.2 River as a Source of supply

The water received from precipitation i.e. rain or melted snow is the surface water which

flows in the form of rivers, streams, lakes and ponds. In India, many cities like Delhi, Calcutta

and Ahmadabad derive their water supply from rivers. The principal advantage of river as a

source of water supply is the large quantity of water available for supply throughout the year.

However, since water has to travel a long distance from the source located in mountains where it

is fairly pure to the towns in plains, its quality deteriorates as river more or less serves as a

natural drain for all discharges from the region. Though river water may be softer than ground

water, it contains large amount of organic matter. Besides, it picks up lot of suspended matter,

clay, silt etc. and becomes muddy in appearance.

Being easily accessible, rivers are freely used for washing, bathing etc. In India, it is

usual for dead bodies to be burnt on the banks of rivers. Besides, places of pilgrimage are

normally situated of water as a source of water supply. Pollution may also be caused by

discharges of trade effluents from industries. It is, therefore, necessary that river water should be

thoroughly treated and protected before it can be made as a source of water supply for towns.

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2.2.3 Quality of surface water

Impurities in water normally are of two types, suspended and dissolved. The surface

waters are characterized by the suspended impurities whereas the ground waters are generally

free from the suspended matter but are likely to contain a large amount of the dissolved

impurities, which they gather during the course of their travel in the underground strata

comprising rocks and minerals. The suspended matter often contains the pathogenic or disease-

producing bacteria; as such surface waters are not considered to be safe for water supply without

the necessary treatment. Ground waters are comparatively safer and fit for use with or without

minor treatment only.

The rain water is soft, has a flat taste and is free from contamination. As however, rain

falls through the air, it collects dusts and gases from atmosphere and becomes impure. Where

rain water is collected in storage tanks, it may pick up impurities and is therefore required to be

disinfected before use for drinking. However, because of the soft nature of the water, it finds an

excellent use for washing purposes.

The river water varies in quality. The variation is caused by the great difference in the

maximum and minimum flow. The maximum flow is caused by high floods, resulting in an

increase in turbidity and bacteria due to the surface wash brought into the river. The minimum

flow is due to the flow of ground water into the river, resulting in the decrease of turbidity but

increase of dissolved impurities. The river water is also usually found to be contaminated with

sewage or industrial waters from towns and cities. The river water, therefore, must be

thoroughly treated before supplying for public use.

2.2.4 Impurities in Water and their Importance

Impurities in water may be classified as follows

(a) Physical Impurities.

(b) Chemical Impurities.

(c) Bacteriological Impurities.

The physical impurities give taste, odour, colour and turbidity. Taste and odour may be

caused due to the presence in water of organic matter dissolved during passage through the

ground or from industrial wastes or due to micro-organism such as algal growth. Turbidity is

caused by the suspended and colloidal matter while colour may be due to the presence of

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mineralogical compounds such as iron oxide etc. Physical impurities do not have a direct

relationship with health but produce many indirect consequences. Turbid water may protect

pathogens (disease-producing micro-organisms) from the effects of chlorination and it may

contain mineral matters that irritate stomach lining. It is often observed that a safe water supply

that has a disafgreeble taste and odour is likely to be passed up by people for unsafe water that

looks and tastes good. The chemical impurities may be either inorganic or organic.

The bacteriological impurities are caused by the presence in water of the pathogenic or

disease-producing type of bacteria making water dangerous for human consumption and health.

From the public health point of view, therefore, bacteriological impurities are the most

important. The pathogenic bacteria are generally inherent in the coliaerogenous or Coliform

group of bacteria of which the Bacillus coliformerly known as B coli (and now called the

Escherichia coli or E coli) is important. The E coil bacteria inhabit the intenstinal tracts of

warm-blooded animals and human beings and appear in very large number in their daily faecal

discharges and also in crude sewage. They by themselves are not harmful but their presence

serves to indicate the possible existence in water of the pathogenic type of bacteria such as the

typhoid bacillus etc., which may be the cause of water pollution. It is, therefore, important for

tests to be carried out to indicate the presence or otherwise of E coli before declaring water

absolutely fit for human consumption.

The source of water to any treatment plant can be either a surface or subsurface source

supplying through dug well, shallow and deep well and bored well. The raw water can be

protected from any kind of pollution or contamination, activates which adversely affected on

human health, economy or good environment.

2.2.5 Surface Water Treatment System

The sequence of water treatment units in a water treatment plant mostly remains same, as

the principle objectives are to remove turbidity and disinfection to kill pathogens. The first

treatment unit in a water treatment plant is aeration, where water is brought in contact with

atmospheric air to fresh surface water and also oxidizes some of the compounds, if necessary.

Many Water treatment plants do not have aeration system. The next unit is chemical addition or

flash mixer where coagulant (mostly alum) is thoroughly mixed with raw water by way of which

neutralization of charge of particles (coagulation) occurs. This water is then flocculated i.e

bigger floc formation is encouraged which enhances settlement. The flocculated water is then

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taken to sedimentation tanks or clarifiers for removal of flocs and from there to filters where

remaining turbidity is removed. The filtered water is then disinfected, mostly with chlorine and

then stored in clear water reservoirs from where it is taken to water distribution system

2.2.6 Aeration

This is the process of bringing waters into intimate contact with air with the object of

driving out objectionable dissolved gases and oxidizing other soluble compounds present in the

ground waters or in stagnant waters of pools and reservoirs.

Aeration is effected in many ways- (i) by causing the waters to flow over weirs and

waterfalls called Cascade aerators, (ii) by dropping water through perforated plates, (iii) by

forcing it through spray nozzles, (iv) by filtering through perforated trays, coke beds, and (v)

through special devices which aspirate air by diffusion through porous plates. The spray nozzle

is the most effective aerator. Aeration is effective in removing 70 to 75 percent of the odours.

Removal of carbon dioxide is equally high.

Aeration is the one of the important unit operation of gas transfer. The aim of the aeration

is to create extensive, new, and self-renewing interfaces between air and water, to keep

interfacial films from building up in thickness.

The objectives of aeration are as follows

It removes tastes and odours caused by gases due to organic decomposition.

It increases the dissolved oxygen content of the water.

It removes hydrogen sulphide, and hence odour due to this is also removed.

It decreases the carbon dioxide content of water, and thereby reduces its corrosiveness

and raises its pH value.

Due to agitation states, so that these can be precipitated and removed.

It is also used for mixing chemicals with water, as in the Aeromix process and in the use

of diffused compressed air.

2.2.7 Flash Mixer

In a Flash Mixer, the rapid mixing is caused in a rectangular chamber, by the revolutions

of a propeller fixed to a propeller shaft and driven by an electric motor. Flash mixer is designed

so that the displacement capacity of the impeller is greater than the maximum flow through the

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chamber so that the alum solution and water are folded together in one quick mix.

Consequently, alum consumption is held to the necessary optimum for adequate treatment. The

detention period is generally to 1 minute, velocity of impeller 3 to 10 revolutions per minute and

the velocity of flow at the periphery less than 75 cm per second.

In a Flocculator the slow striing is mechanically brought about inside a circular tank

equipped with paddles revolving on a vertical shaft. The paddles operate at 2 to 3 revolutions

per minute. Time allowed for flocculation varies from 30 to 60 min.

In the clarifier, small scrapers are attached to radial arms moving towards s sludge-sum

from where sludge can be continuously removed.

The mechanically-operated mixing basins have such advantages over the baffle-type

basins as (i) reduction in the amount of coagulant (as much as 40 percent) due to more thorough

mixing (ii) negligible loss of head, which in the case of baffle-type basins is higher, about 0.6m,

(iii) greater flexibility of operation and (iv) lesser cost of installation.

Fig. Flash mixer

2.2.8 Clariflocculator

Clariflucculator is widely use in India for the reason that both the flocculators and

sedimentation process are effectively incorporated in the single unit. These are provided a central

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flocculation chamber consisting paddles rotating on their vertical axis with wide outlets ports at

the bottom to the clarified zone to maintain the low velocity.

2.2.8.1 Flocculation

From the mixing basin water is taken to flocculators for flocculation. Flocculation of

slow mixing is the hydrodynamics process which provide adequate opportunity for the micro-

flocs formed during the process or rapid mix to come together to form aggregates of readily

settable size. Mechanical flocculator consists of tank provided with paddles for stirring of water,

and hence these are also known as flocculator. Depending on the direction of flow water in the

tank the mechanical flocculators are classified as.

1) Longitudinal flow flocculator and

2) Vertical flow flocculator

2.2.8.2 Sedimentation Tanks or Clarifiers

A sedimentation tank also called setting tank or clarifier, the operation involved is either

to detain unflocculated water containing heavier and suspended. Impurities and thereby cause

them to settle out or to let the flocculated water flow in from the mixing basin and allow the

flocculent precipitate to settle out of suspension. Tanks involving operation of the first kind are

called Plain Sedimentation Tanks and those of the second kind as Chemically-aided

Sedimentation Tanks.

In operating these tanks, two methods have been in use (i) the intermittent or fill and

draw method in which the sedimentation takes place during the period the tank stands full, after

which the rank is empties. (ii) The continuous method in which water is allowed to flow

continuously and slowly through the tank while the sedimentation takes place. The first of these

methods i.e., the fill-anddraw method is now obsolete because it requires considerable labour

and has no comp0ensating advantages. Sedimentation tanks are now almost exclusively

operated on the continuous-flow method.

The mixing process not only mingles the coagulants with the water but has a very great

effect upon the formation of the floc. It is usual to introduce the chemical at some point of high

turbulence in the water. After the dose of the chemical is added to the raw water, through mixing

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is provided by the flash mixer. Rapid mixing is an operation by which the coagulant is uniformly

dispersed through the incoming volume of raw water. This help in the formation of micro flocs

and result in proper utilization of chemical coagulant preventing localization of concentration

and premature formation of hydroxides which lead to less effective utilization of coagulation.

The flash mixer is provided with an agitator for thorough mixing of chemicals with raw water.

The detention period generally adopted for these tanks is 2 to 2.5 hours with surface overflow

rate ranging from 30 to 40 m3/day/m2.

Fig. Clarriflocculator

2.2.9 Filtration

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Filtration is the most relied water treatment process to remove particulate material from

water. Coagulation, flocculation and settling are used to assist the filtration process to function

more effectively. The coagulation and settling processes have become so effective that some

times filtration may not be necessary. However, where filtration has been avoided, severe losses

in water main carrying capacity have occurred as the result of slime formation in the mains.

Filtration is still essential.

.

2.2.9.1 Classification of filter

1) On the basis of filtration rate

a) Slow sand filter b) Rapid sand filter

Rapid sand filter are also classified as

a) Rapid sand b) Presser filter

Fig. Rapid sand filter

In conventional water treatment, rapid sand filters are commonly adopted.

The capacity of the rapid sand filters should be such that the number of unites can take

care of the total quantity of water to be filtered. The smaller the number of units, the favor the

appurtenances but the larger the wash water equipment that will be required, while designing

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large size filters one must consider the rate at which wash water dust be supplied and the

hydraulic problems for securing uniform distribution of wash water due to the large area. A

maximum area of 26 m2 for a single unit can be provided for plants of greater than 130 m3/hr.

a) Sand shall be of hard and resistant quartz and free of clay, fine particles, soft grains and

dirt of every description.

b) Effective size shall be 0.45 to 0.70 mm.

c) Uniformity coefficient shall not be more than 1.7 also not less than 1.3.

d) Ignition loss should not exceed 0.7 percent by weight.

e) Soluble fraction in hydrochloric acid shall not exceed 5% weight.

f) Silica content should not be less than 90%.

g) Specific gravity shall be in the range between 2.55 to 2.65.

h) Wearing loss shall not exceed 3%.

2.2.9.2 Depth of Sand

Usually the sand layer has a depth of 0.60 to 0.75 m, but for higher rate filtration when

the coarse medium is used deeper sand beds are suggested. The standing depth of water over

filter varies between 1 to 2 m. The free board above the water level should be at least 0.5 m so

that when air binding problems are encountered, it will facilitate the additional levels of 0.15 m

to 0.30 m of water being provided to overcome the trouble.

2.2.9.3 Filter Sand

The selected filter sand should be free from clay, loam, vegetable or organic matter. It

should also be uniform and of proper size. If the sand is too fine, it tends to quickly clog,

causing a greater loss of head in the filter and if it is too coarse, it will permit suspended solids

and bacteria to pass through the voids between the sand grains. It is usual, therefore, to classifuythe filter sand by such characteristics as the effective size, the uniformity coefficient and the

percent size.

Effecftive size of the sand is defined as the sieve size in mm which permits 10 percent of

the sand, by weight to pass or in other words, as the size of the grain that is larger than 10

percent by weight of all the particles comprising the sand. This expression would merely indicate

the minimum size of 90 percent by weight of the sand. This does not give any information about

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the degree of variation in the sizes of the particles or about the sizes of the largest and smallest

grains. It is found that considerable variation in individual grain size adversely affects the

efficiency of the filter.

Uniformity Coefficient of sand is an expression of the degree of variation. This may be

defined as the ratio between the sieve size that will pass 60 percent by weight to the effective

size or in other words, as the ratio of the particle size which isn coarser than 60 percent by

weight of the sand to the effective size of sand. Thus, if sand has an effective size of 0.50 mm

and 60 percent of sand passes a 0.80 mm. Sieve, the uniformity coefficient = .

Recently, with certain special sands, it is found that the expression percent size is more

suitable than effective size. Percent size may be defined as the size of the grain that has the

given percent by weight, of materials finer in size. On this basis, sands, 1, 10, 60 and 90 percent

sizes are specifies. Thus a percent size of 10 means that 10 percent of the sand is smaller than the

grain size given. The advantage of this method is that the percent size of sand can be directly

specified without plotting as is done for the effective size determination. This amounts to a

simplified procedure.

Percent Size Distribution of Filter

Sand Grains.

Percent

Size

Grain size, mm

Fine Medium CoarseMin. Max. Min. Max. Min. Max.

1 0.26 0.32 0.34 0.39 0.41 0.4510 0.35 0.45 0.45 0.55 0.55 0.6560 0.53 0.75 0.68 0.91 0.83 1.0890 0.93 1.50 1.19 1.80 1.46 2.00

2.2.9.4 Filter Washing

This is carried out by the processes of air scour and backwashing i.e. by sending air and

water respectively upwards through the filter bed.

As the filter is drained out leaving a few cm. Depth of water standing above the top of the

bed, compressed air is sent under pressure through the under-drainage system for about 2-3

minutes. This agitates the mass of water and the dirt from the surface of sand grains is loosened.

An upward flow of water from a high level tank is now sent through the bed. This causes the

sand-bed to expand, agitate the sand grains and wash off the surface-deposits, which are then

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collected in troughs placed 15-30 cm above the top of the filter and carried away to the wash-

water drain. It is important that the velocities of air scour and back flow are properly controlled

so that the sand grains are not bodily carried out with the surface wash-water.

In the air wash system, the air is forced through the under-drains before the wash water is

introduced. Free air of about 36 to 45 m/h (600 to 900 lpm/m 2 of the filter area) at 0.35 kg/cm2is

forced through the under drain until the sand is thoroughly agitated, for a period of about 5

minutes, following which wash water is introduced through the same under at a rate of 24 to 36

m/h (400 to 600 lpm/m2of area). In the practice backwashing employing conjunctive air and

water wash air is usually applied at a rate of 45-50 m/h and water 12-15 m/h.

2.2.10 Disinfection

Chlorination became the accepted means of disinfection and it is the single most important

discovery in potable water treatment. Recently, however the concern over disinfection by-

products (DBPs) produced by chlorine has given new impetus to investigating alternative

disinfectants. Disinfection of potable water is the specialized treatment for destruction or

removal of organisms capable of causing disease, it should not be confused with sterilization,

which is the destruction or removal of all life.

Pathogens (disease producing organisms) are present in both groundwater and surface

water supplies. These organisms, under certain conditions, are capable of surviving in water

supplies for weeks at temperatures near 21 C, and for months at colder temperatures.

Destruction or removal of these organisms is essential in providing a safe potable water supply.

While the exact effect of disinfection agents on microorganisms is not clearly understood, some

factors that affect the efficiency of disinfection are as follows

Type and concentration of microorganisms to be destroyed

Type and concentration of disinfectant

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Contact time provided

Chemical character and

Temperature of the water being treated

2.2.10.1 Chlorination

Chlorination is the application to water of small quantities of chlorine or chlorine-

compounds. The dose applied is generally less than 1 mg/l. The dose applies is tity varying from

a trace to about 0.05 to 0.20 mg/l. The amount of chlorine so required to be added depends upon

the chlorine demand of water, which is the difference between the amount of chlorine added and

the amount of chlorine remaining at the end of a contact period of 10-20 minutes.Chlorination possesses great disinfecting powers, as such this method is universally

employed for disinfecting public water supplies. Chlorine reacts with water to produce

hypochlorous acid (HOCI) and hypochlorite ion (OCI), which are together known as free

available chlorine. The chemical action may be represented as

Cl2 + H2O --- HOCI + HCI

HOCI = H+ + OCI-

If ammonia is also present in water, other compounds formed are monochloramine (NH2CI) and

dichloramine (NHCI2) which are together known as combined available chlorine. These resulting

chlorine-compounds either in the form of free or combined available chlorine interferes with

certain enzymes in the bacterial cell-wall forming a toxic chloro-compound thus destroying the

bacterial completely.

Another theory ascribes the destruction of bacteria to the liberation of nascent oxygen

(HOCI=HCI+O) which oxidizes the organisms. This theory is now considered inadequate and

obsolete on the grounds that the quantity of nascent oxygen produced is too less for the purpose

and further that other equally powerful oxidizing agents like hydrogen peroxide do not possess

the same disinfecting power. Chlorine is the chemical predominantly used in the disinfection of

potable water supplies. The first application of chlorine in potable water treatment was for taste

and odour control in the 1830s. At that time, diseases were thought to be transmitted by odour.

This false assumption led to chlorination even before disinfection was understood. Currently,

chlorine is used as a primary disinfectant in potable water treatment. Other use include taste and

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odor control, algae control, filter-media conditioning, iron and manganese removal, hydrogen

sulfide removal, and color removal.

Through physio-chemical process such as aeration, coagulation, flocculation,

sedimentation and filtration assist in removal of microorganisms to varying degree, these can not

be relied upon to provide safe water. As indicated in the previous section a consideration amount

of bacteria and other micro-organisms present in raw water are removed by filtration, but the

water obtained from filter still contain bacteria and other micro-organisms, some of which may

be pathogenic. The water obtaining from filter is therefore not safe for drinking purpose, it is

necessary to kill the disease producing bacteria and other micro-organism present in it. The need

for disinfection in ensuring protection against transmission of water borne diseases cannot be

overemphasized and its inclusion as one of the water treatment process is considered necessary.

Chlorination is achieved by mean of either liquid or gaseous chlorine of bleaching powder.

2.2.10.2 Forms of chlorination

Depending upon the stage of treatment at which chlo0rine is applied to water and also

upon the expected result of application of chlorine may be of the following form:

i. Plain chlorination (simple chlorination)

ii. Pre-chlorination vi. Break point chlorination

iii. Post-chlorination vii. Super-chlorinationiv. Double or multiple chlorination viii. Dechlorination

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Table showing unit operations and unit processes of watertreatment plant.

Sr .No. Units UO (or) UP Principle Applications

1. Micro strainer UO Remove algae and plankton from thewater

2. Aeration UP Strips and oxidizes taste and ocausing volatile organics and gasesoxidizes iron and manganese. Aersystems include gravity aerator, saerator, diffuser and mechanical aerato

3. Mixing UO Provides uniform and rapid distributiochemicals and gases into the water.

4. Pre-oxidation UP Application of oxidizing agents suchozone, potassium permanganate,

chlorine compounds in raw water another treatment units; retmicrobiological growth and oxidizes todor and colour causing compounds

5. Coagulation UP Coagulation is the addition and rmixing of coagulant resulting destabilization of the colloidal particleformation of pin-head floc

6. Flocculation UO Flocculation is aggregation of destabiturbidity and colour causing particleform a rapid-settling floc

7. Sedimentation UO Gravity separation of suspended solidfloc produced in treatment processes.used after coagulation and flocculationchemical precipitation.

8. Filtration UO Removal of particulate matter percolation through granular mFiltration media may be single (santhracite, etc.), mixed, or multilayered

9. Disinfection UP Destroys disease-causing organismwater supply. Disinfection is achieveultraviolet radiation and by oxid

chemicals such as chlorine, bromiodine, potassium permanganate, ozone, chlorine being the most commused chemical

Note: UO Unit OperationsUP Unit Process

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METHODOLOGY & MATERIALS

Methodology

Evaluation procedure followed in water treatment plant for achieving the objectives of

the study work were detail study of the plant performance including operation problems. Testing

and plant safety. The analysis was carried out in accordance with the following steps, Collection

of basic data, plant observation, performance evaluation, and appraisal of laboratory as

summarized in tables.

Table 3.1: Summary of Evaluation Procedure

Collection

Of Basic

Data

Treatment flow sheet and plant design data, plant layout,

engineering details including design, drawing and operating

reports for individual treatment unit. Characteristics of plant

influent and effluent, Laboratory facilities, plant persons (i.e. no.

of staff, their qualification and experience), and other relevant

details such as power consumption etc.

Plant

observati

ons

Pumping and flow measurement, water quality, pre-treatment,

chemical dosing, chemical mixing and flocculation,

sedimentation ( clarity of settled water), filtration (Influent and

effluent turbidity, back washing operation, filter appearances

and problems)Performan

ceEvaluatio

n

Flow measurement, sampling and analysis, assessment of

individual treatment units with engineering and water qualityparameters as appropriate. Identification of deficiencies, in

operation and maintenance, if any.Laborator

y

evolution

Sampling records, instrument and Equipment used, and review

of analysis results.

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3.2 Activities, Operations & Design of Water Treatment Unit

3.2.1 Raw water Sump and Pump House

Pure water sump is provided for storing the filter water & pumps it for distribution to

meet the demand of portable water. The filtered water, after the chlorination for disinfection

flows to the pure water sump through the conveying main. The pure water sump is provided with

an overflow arrangement.

The sump and pump house has constructed near to the Bormada Ghat of Wainganga

river basin. The water is first collected by intake structure and sump is R.C.C. tank the size of is

18 m x 8 m x 3.50 m and the capacity of sump 520 m3.

Here a pump 2 HP, two pumps of 1 HP & 20 mud pumps are in used.

3.2.2Aeration

The raw water discharges at the center of the concentric aeration fountain through the

central inlet shaft & flows down the step to the peripheral launder. Weirs and waterfalls of any

kind are cascade aerator. Cascade is of a series of four step of concrete. Water is allowed to fall

through height of 1 to 3 meter, and due to this it comes into close contact with air. The reduction

of CO2 is usually in the range of 50 to 60%.

The diameter of bottom cascade fountain is 6 m and top cascade is 2.45. R.L of cascade

in 308.220 m and bottom cascade is 307.780 m. 1.4 m width of collecting chamber is provided

with height 1 m. The aerated water is collected in open channel of 1200 mm wide Parshall flume

for measurement of flow and then transferred to flash mixer.

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Table 3.2 Design criteria for cascade aerator

Objective To extensive, new, and self-renewing interfaces between air and water, to

keep interfacial films from building up in thickness.

Design

Parameter

Design capacity Rate of flow 30 MLD

Assuming G.L. 305.685 m

No. of Cascades 4 Nos.

Lip of Aerator fountain 308.500 m

Top level of 1st cascade 308.320 m




Outer Diameter pf Vertical Shaft 0.60s m

Inner Diameter pf Vertical Shaft 0.560 m

Total Diameter 1st cascades 3.00 m




Size of water channel 2.0 m(wide) x 2.00 m

(depth) (0.90 m water depth

+ 10 cm free board)

Top level of water channel 307.780 m

Bottom level of water channel 306.600 m

Bottom level of vertical shaft 303.500 mVelocity 0.60 m/sec

Expected

Output

It should increase in Dissolved Oxygen and remove other gases from water.

& completely removing of taste and odours cascade by gases.

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Fig. 3.2 Aerator

3.2.3 Raw water flow measurement

This unit is provided to monitor the raw water entering into the treatment plant. A flow

meter is installed for measuring the raw water flow. A Parshall flume of 1200 mm wide has been

provided in the raw water inlet chamber. The flow measuring device with a capacity of 30 MLD

to measure flow. The type flow measuring element is rectangular notch type. The measuring

device is of float operated flow type indicator gauge pedestral type with flat chamber which is

not in working condition. The variation of water level in the flot chamber is transmited to he

pointer by the movement of the float & the pointer indicates the raw water flow.The width of

throat of this is 1000 mm.

3.2.4 Coagulant dosing chemical house

This unit is provided of an instantaneous & through out mixing of chemicals that are

added to the raw water. There are four no. of tanks, two for alum solution & two for lime

bleaching powder solutions. The effective capacity of tank are 2600 liter.The alum dose to be

administrated is 26.00 kg/hr.The capacity of storage of alum is for 4 months and the size of chemical house is 10.0 m

x 3.50 m. There is a unit having size Diameter 2.30 m & 3.00 m (depth). The design rate of flow

is 30 MLD. Presently they are using alum bricks in liquid from at raw water channel through a

perforated plastic pipe located about 50 cm above the water surface, some of perforation was

found clogged.

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3.2.5 Flash Mixer

The measured quantity of raw water along with chemical dosed enters into side jacket

and is admitted in the flash mixer through the bottom opening in the well. The flash mixer is 2.30m diameter and 3.0 m deep with four baffle walls for better mixing of 12.5 MLD capacities. The

motor of 1 HP has been provided with 500 rpm. The flash mixer is well equiped with a suitable

speed agiator forensuring the proper mixing of chemicals with raw water. By pass arrangement is

also provided for the raw water to the filter beds, when the chlorriflocculator is under

maintenance. One no. of M. S. shutter is provided for bypass utility.

Table 3.3 Design criteria of flash mixer

Objective To disperse the chemical coagulant effectively in the raw water thereby

causing complete destabilized of colloidal impurities and formation of micro

floc.

Design

parameter

Designed capacity 12.5 MLD

Diameter of mixer 2.30m

Water Depth 3.00m

F.S.L. 306.250m

Bottom level 303.250m

Detention period 1minValue of G to be achieved 300/sec

Free board 0.40m

Motor H.P. 1 H.P (Kirloskar make gear)

Velocity Gradient 300/sec

Expected

output

Complete destabilization of colloidal impurities and formed micro flocs

which can be readily agglomerated in the sequence process of slow mixing

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3.2.6 Clariflocculator

Along with the object of clariflocculator to form distinct setteable flocs during

flocculation & their removal by gravitational setting in the clarifying zone. The clear water

overflows leaving behind the settleable solids, the coagulated water enters at about of

flocculator. The flocculator has a diameter of 9.72 m while the clarifier has a diameter of 23.90

m and depth 3.55 m. Along the periphery of tank the channel has been provided with V-notch.

The settled flocs are colected in the central circular channel around the inlet column by a set of

scraper arms fixed to a rotating M.S. Bridge is 48 rounds per hour. The central sludge channel is

provided with a local depression to accommodate a chamber from where the collected sludge is

withdrawn periodically for disposal through the manhole. The clear water leaving behind the

setteable solids overflows into the peripheral launder & is led to the subsequent unit for further

treatment.

Table 3.4 Design criteria of Flocculator

Objective To Produce readily settable floc destabilized colloidal particles.

Design

parameters

No. of units 1 (Radial flow clarifier with conc. flocculator)

Design flow through

clariflocculator unit

520.00 m2/hr

Detention period 30 min(10-30 minutes )

Diameter 9.72 m

Velocity Gradient 30 sec-1(10-75 sec-1)

Surface overflow rate 21.88 m3/m2/day

Weir loading 17.46 m3/m/day

Expected

Output

The flocs formed during flocculation settles readily in the sedimentation basin

and filter box. The floc strength should be sufficient to withstand shearing that

may be encountered during its travel to the sedimentation basin.

Table 3.5 Design criteria of Clarifier.

Objective To Objective of the sedimentation is to permit effective sedimentation and

flocculation process.

No. of units 1 (Peripheral type)

Capacity of each unit Design flow

through clariflocculator unit

520.00 m2/hr

Detention period 150 min.

Diameter 23.90 m

RPM of blades 10 RPM

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Design

Parameters

Floor slope 1:12

Weir loading 17.46 m3/day/m2

Surface loading 21.88 m3/m2/day

Turbidity < 10 NTU

Velocity of water in collecting

channel

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Fig.3.4 Clarifier with flocculator

3.2.7 Filter

The clarified water collected in the peripheral launder around the clariflocculator flows

into the filter inlet channel. The totals of 4 number rapid sand gravity filters have been provided,

having total capacity of 520 m3/hr. The filters are designed to operate under constant rate,

constant head principle. The filter is designed for filtration rate 5 m 3/m2/hrs. The area of each

filter bed is 26.0 sqm. The each bed having two part of same size is 10.00 m x 4.50 m x 2.00 m(depth). The F.S.L. of bed is 304.500 m and outlet level 302.00 m with the filter operation head

of 1.6 to 1.8 m.

The performance of filter was respect to turbidity, pH, dissolved oxygen, total solids and

suspended solids. And also with respect to uniformity coefficient of sand, turbidity, pH, Total

solids & Suspended Solids of raw water, back wash water & filtered water. The expected design

criteria of a filter is given in table.

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Table 3.6 Expected Design Criteria of Filter

Objective To Remove the turbidity, precipitates from preceding units and bacteriological

matter in the water.

Design

Parameters

No. of beds 4 nos.(Rapid gravity sand filters)

Rate of filtration 5 m3/m2/hrs

Rated flow in each filter 520/4 =130 m3/hrs. of 12.10 MLD

Flow 12.5 MLD

Wash water rate 600 LPM/m2

Air scour rate 750 LPM/m2

Blower capacity 1800 RPM @0.35 Kg/cm2(two)

Filter inlet velocity 0.8 m/sec

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3.3.8 Chlorination

Chlorination is practiced to disinfect the filter water to make it suitable for portable use.

The filter water from the filter beds flows through the pure water channel to the purewater sump. Bleaching powder solution is added to the filtered water in pure water cannel for

disinfection of the water. Appropriate quantities of bleaching powder solution so as to leave the

desired residual chlorine in the filtered water are added through the constant head box placed on

the pure water channel. There is one unit of Gravity type of chlorination provided & is in

working. The maximum dose of chlorination is 2 mg/lit for a flow of 6 MLD for a capacity of

1.5 kg/hr.

Table 3.8 Design considerations for disinfection

Objective The objective of chlorination is effective destruction of or inactivation of

pathogenic organisms.

Design

Parameters

It should be capable of destroying the pathogenic organism present. Within the

contact time available and not unduly influenced by the range of physical and

chemical properties of water encountered particularly temperature, pH and

mineral constituents.

It should not leave product of reactions which render concentration to deal with

small possible recontamination.

It should posses the property of leaving residual concentration to deal with

small possible recontamination;

It should be amenable of detection by practical, rapid and simple analytical

techniques in the small concentration ranges to permit the control of

disinfection process.

Free available residual chlorine, mg/lit plant efficient at normal pH and 30 min

contact time should be 0.2-0.3 ppm

ExpectedOutput

The chlorinated water should be totally free from pathogenic organism i.e.coliform count should be zero.

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3.2 Sampling Techniques

Water samples were collected from sample points viz. sample from source, aerated water,

filtered water & clear water. It is drawn for analysis of temperature, pH, turbidity, D.O.,

alkalinity, hardness, total solids, residual chlorine & the coliforms. The evaluations were done to

check whether the plant is giving the desired output or not. The collected samples full analysis

was carried out in District Health laboratory, Gadchiroli & Namdeorao Poreddiwar College of

Engg. & Technology, Gadchiroli. Analysis done to check physical, chemical & bacteriological

parameters. The obtained results compared with standards of drinking water.

While collecting the samples following guidelines have been followed

Sample collected in clean dry & stoppered bottles.

The bottles rinsed thoroughly before collecting of samples

While collecting samples from the sampling through, the lines are to be flushed at least

for five minutes before the samples collected. This enables the removal of accumulated

solids (if any) in the line.

Stopper the bottle after collection of sample.

Attached a tad on the bottle indicating date, name of sample & test to be carried out.

The water quality variations could be of two types random & seasonal or cyclic. Random

variation due to sudden rainfall in the catchment or sudden release of water from the storage e.g.

dam increased frequency may not help much as such variations are highly unpredictable. Thus

within the available resources it is not cost effective to cover such variations. As in the present

study the water body is having seasonal changes, the sampling frequency is kept throughout the

year.

The techniques which adopted for analysis of various parameters are as follows

The water temperature was measured using the mercury Thermometer. The reading was

taken by dipping directly the thermometer in the water from different units of WTP. It was

recorded in degrees Celsius 1 digit after the decimal point.

The digital pH meter was used to measure pH of samples from different units.

Turbidity of water was tested by the Aplab Turbidity meter.

Winklers method was adopted to determine the Dissolved oxygen. Magnous

sulphate solution, alkali iodide azide reagents, conc. Sulphuric acid, starch, standard

sodium thiosulphate titrant (Na2S2O3), acetic acid & potassium iodide (KI) crystals

were used in this method to determine dissolved oxygen.

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Alkalinity of water samples were determined by titrating the water sample against

standard sulphuric acid using phenophthalin & methyl orange indicator.

The EDTA method was used to determine the total hardness present in the water

sample. In this method the water sample is titrated against the standard EDTA solution

using Erichrome Black T.

Evaporation technique was used to find the total solids present in the water

sample. In this method the sample is evaporated in a evaporating dish. After

evaporation the difference of the weight of water sample before the evaporation &

after the evaporation gives the total solids present in the water samples.

The water sample was titrated against the sodium thiosulphate (Na2S2O3) using

starch indicator to find the residual chlorine present in the water.

Pathogens present in the water causes the diseases to the consumer. The most

probable number of coliform was found using multiple tube dilution technique

(MTDT).

In water quality monitoring the various measurement methods, units and significant

figures for different parametrs used are shown in following table

Parameters Units Measurement

Methods

Significant

after decimalColour Visual method

Odour Manual

Temperature C Thermometer 1

pH pH meter

Electrical

Conductivity

S/cm Conductivity meter 0

Dissolved oxygen mg/L DO Meter or

Winklermodified method

1

Turbidity NTU Nephelometer 1

Total Dissolved

Solids

Mg/l Gravimetry 0

Ammonical

Nitrogen(NH4-N)

mgN/L Colorimetry 1

Nitrite + Nitrate-N mgN/L Colorimetry 1

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Total Phosphate mg/L Colorimetry 4

Orthophosphate mg/L Colorimetry 4

Biochemical

Oxygen

Demand (BOD

mg/L DO consumption in

3 days

at 27 C

1

Chemical Oxygen

Demand (COD)

mg/L Potassium

dichromate

method

1

Sodium mg/L Flame photometry

Potassium Flame photometry

Calcium mgCaCO3/

L

EDTA Titrimetric 1

Magnesium mgCaCO3/L

EDTA Titrimetric 1

Carbonate as CaCo3 mgCaCO3/

L

Titrimetric 1

Bicarbonate as

CaCo3

mgCaCO3/

L

Titrimetric 1

Chloride Mg/l Argentometric

titration

1

Sulphate Mg/l Turbidimetry 1

Fluoride Mg/l Ionmeter,

colorimetry

2

Boron Mg/l Ionmeter, curcumin

method

2

Total Coliform No./100ml MPN or MF method 0

Fecal Coliform No./100ml MPN or MF method 0

% Sodium - Calculation 2

SAR - Calculation 2

1 Specific ParametersArsenic Ug/l Cold vapour AAS 1

Mercury Ug/l Cold vapour AAS 1

All other heavy

metals

Ug/l AAS 1

Pesticides and other

organics

Ug/l GC, GCMS 1

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OBSERVATION, RESULT & DISCUSSION

The observations made during the visit to WTP after considering all design criteria of all

treatment units, on site evaluation studies & after sampling & analysis with a view to study the

characteristics of raw water & treated water, to check the performance of treatment units at

various stages of water treatment plant plants are as follows

1. On-site performance evaluation studies.

2. Sampling & analysis

4.1 Observations On site performance evaluation studies

During the visit to WTP the following observations were made The water is received to treatment plant from surface source from Wainganga river

throughout the year. The principal advantages of this river as a source is that sufficient

quantity of water is available. Thus treatment plant can run steadily.

Water is colorless, tasteless, and odorless. It is an excellent solvent which can dissolve

most minerals that come in contact with it. It contains chemicals and biological impurities

i.e. suspended and dissolved inorganic and organic compounds and micro organisms.

These compounds may come from natural sources.

The water treatment plant is having capacity 12.5 MLD. But in practice it is treating

maximum 6 MLD of water & supplying it to the city.

Temperatures of raw & clear water were in the range of 220 to 270 C in winters & less than

350 C in summers.

Aeration was in good working condition & all water was coming out through this unit

without any leakages.

The water flows in normal flow condition was 520 m 3/hr whereas designed discharge was

990 m3/hr.

Alum brick is being added as coagulant in the WTP. The raw water is very clean having

turbidity less than 10 ppm during non-monsson period. The alum was being added even

for this less turbidity & alkalinity.

Jar test was not carried out regularly & coagulant dose is added arbitrarily.

The chemical house was having four no. of tanks, two for alum solution & two for lime

bleaching powder solution, each tank having capacity of 2600 liter.

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The tapered flocculation units with flocculator of varying speeds are in use. The setting

tank is with hopper bottom having mechanical scraping arrangement and was cleaned once

in a year. Though the flocculator is having varying speed the constant speed of 10 rpm &

overflow rate 21.88 m3/m2/day were maintained throughout the year.

Clarifier was cleaned twice in a year and the sludge was disposed off in nearby drain.

There was no reuse of backwash water.

The water treatment plants has four no. of rapid sand filter units & sand as a filter

media.The effective size of sand in the range of 0.45 to 0.7 mm. The area of each filter bed

was 26 m2 & having rate of filtration 5 m3/m2/day. Filter runs for 24 hours except at the

time of backwashing. Proper housekeeping & illumination with tube lights & routine

maintenance were found in filteration unit. Except the depth of filter bed were lowered &

need to replace the beds of sand media.

Filter backwash waters and sludge from water treatment plant were being discharged into

nearby drains.

The charts showing the details of water treatment plant units such as their sizes,

specifications, layout etc. was not available.

The plant was using the bleaching powder for disinfection. The operation and maintenance

of the chlorinator was satisfactory and chlorine dosing was on approximation.

Filter operator & pump operator were well aware of their duties & running the unitsatisfactory.

Though the plant was established in 2003, all units of plant were in good working

conditions & almost all standards of operation & maintenance work were followed by

plant.

4.2 Observations from sampling & analysis

The analysis of water was undertaken in order to establish the quantity of water. Thisinvolves test for determination of (a) physical analysis which includes colour, taste, odour, and

turbidity etc. (b) chemical analysis which includes determination of pH, hardness, total solids,

residual chlorine, chlorides, iron, manganese and organic matter etc. (c) Bacteriological analysis

to determine its potability i.e. fitness for drinking.

The sample from different treatment units like water from intake, from aeration, filtration

and clear water were collected and analysis done in district health laboratory, Gadchiroli and

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NCET, Gadchiroli. The analysis of various collected samples of WTP is shown in table 4.1 to

4.4.

Experimentation results indicated that the temperature of the entire sample collected

from different units was within the prescribed limit.

The temperature of raw water ranged from 270 to 240 C and of the treated water, the

temperature range was 280 to 250 C. There is slight change in the temperature season wise.

The pH value of the water was more in summer and winter season and less in monsoon

season. The slight rise was occurring in the pH of treated water in summer than the

permissible limit. The range of pH from monsoon to summer was 7.8 to 8.2. And in the

treated water the range of pH was 6.5 to 7.3.

The most important factor in this case was the turbidity. The value of turbidity obtained in

monsoon season was maximum of 86 NTU. Minimum of 6 NTU in winter season. Rapid

sand filter reduced this 59 NTU turbidity up to 1.3 NTU. In treated water the turbidity

ranged from 1 NTU to 6 NTU. The maximum value was in monsoon. The turbidity of

treated water was in permissible limit.

The dissolved oxygen was in more than permissible limit in some sample of raw water

throughout the year ranging from 8.2 mg/l to 9.8 mg/l. The dissolved oxygen in monsoon

season was more than that in summer season.

Alkalinity did not cross the maximum limit and lies within 72 mg/l to 105 mg/l in raw

water and 60 mg/l to 85 mg/l in treated water.

Hardness was more in the raw water about 180 mg/l, but it was successfully reduced to 90

mg/l in monsoon season.

The total solids present in the water were ranging from the 125 mg/l to 235 mg/l from

summer season to monsoon season, the maximum value being in monsoon.

The residual chlorine also ranged within the permissible limit except near the water

treatment plant where it was from 0.5 mg/l to 0.6 mg/l. As near the treatment plant it was

0.5 to 0.6 mg/l. it may become the 0.1 to 0.2 mg/l when it reached to the consumer at the

farthest end

In the multiple tube dilution technique test (MTDT test) in all raw water sample the

bubbles were observed which indicates the presence of coliforms in the water.

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But after the disinfection for all clear water sample no bubbles were observed in the

multiple tube dilution technique test which showed that no coliforms were present in the

treated water.

The adequacy of water treatment from health point of view was ensured by maintaining

the residual chlorine of 0.4 to 0.2 mg/l at the farthest point of distribution system. There is

no facility for MPN testing.

4.3 Discussion and Results

Form the observations made from on site performance evaluation and the analysis

of samples, it is found that the raw water is not having much pollutants. And each unit was

doing its job very satisfactory even after nine years of establishment.

Due to perennial nature of Wainganga river and having 250 meter wide basin, the

sufficient quantity of water is available through out the year.

Water is colorless, tasteless, and odorless, though it contains chemical and biological

impurities i.e. suspended and dissolved inorganic and organic compounds and micro

organisms, which are brought as per standards after going through treatment processes.

All the treatment units of plants were in good working conditions which indicates that the

maintenance work were done on regular basis. Proper house keeping and illuminations

near the filtration units, adequacy in all unit processes were giving satisfactory results.

The turbidity in monsoon was not very high as there is no effluents discharge near the

intake source. The amount of total solid was more.

The presence of pH, alkalinity of raw water was more, which was reduced in

clariflocculator due to formation of sulphuric acid.

The persons working in the water treatment plant are well experienced and paying much

attention for operation and maintenance of water treatment plant.

The quality of intake water is not so poor and keeping all the treatment units well

maintained and providing other facilities like coagulant dose, bleaching powder dose with

respect to seasonal variation, it is possible to improve overall efficiency of water treatment

plant.

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4.4 Conclusion and suggestions

From all the studies of the performance evaluation of water treatment plant at

Gadchiroli, it is concluded that the plant is in good working conditions along with all its

treatment units.

From the sample analysis it is found that there is no much variation in temperature of raw

water, a slight change occurred in treated water.

The various important parameters like pH, turbidity, dissolved oxygen, alkalinity,

hardness, total solids and residual chlorine are within the permissible limit.

All the treatment units of plants were in good working conditions which indicates that the

maintenance work were done on regular basis. Proper house keeping and illuminations

near the filtration units, adequacy in all unit processes were giving satisfactory results.

After carrying out detailed investigation, the following suggestion are discussed,

The green colour of raw water during the winter season was increase due to in phosphate

percentages, which causes problem of algae growth.

In flow measurement channel was not working which were repaired earliest.

Need to determine the coagulant dose on seasonal basis by using Jar test and not to add it

arbitrarily.

Need to replace the beds sand media.

Necessary measures were required to remove the clogging of valves in pipe line due tothe accumulation of silt and corrosion in pipe. One valve was not in working condition.

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