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CHNG II NGUON GOC, THANH PHAN, KHOI LNG

VA AC TNH CUA CHAT THAI RAN

2.1 Nguon Goc Chat Thai Ran

Nguon goc phat sinh, thanh phan va toc o phat sinh cua chat thai ran la cac c s quan trong e thiet ke, la chon cong nghe x ly va e xuat cac chng trnh quan ly chat thai ran thch hp.

Co nhieu cach phan loai nguon goc phat sinh chat thai ran khac nhau nhng phan loai theo cach thong thng nhat la: (1) khu dan c, (2) khu thng mai, (3) c quan, cong s, (4) xay dng va pha huy cac cong trnh xay dng, (5) khu cong cong, (6) nha may x ly chat thai, (7) cong nghiep, (8) nong nghiep. Chat thai o th co the xem nh chat thai cong cong, ngoai tr cac chat thai trong qua trnh che bien tai cac khu cong nghiep va chat thai nong nghiep.

Chat thai ran phat sinh t nhieu nguon khac nhau, can c vao ac iem chat thai co the phan chia thanh 3 nhom ln : Chat thai o th, cong nghiep va nguy hai. Nguon thai cua rac thai o th rat kho quan ly tai cac ni at trong (open areas) , bi v tai cac v tr nay s phat sinh cac nguon chat thai la mot qua trnh phat tan.

Chat thai nguy hai thng phat sinh tai cac khu cong nghiep, do o nhng thong tin ve nguon goc phat sinh va ac tnh cac chat thai nguy hai tai cac loai hnh cong nghiep khac nhau la rat can thiet. Cac hien tng nh chay tran, ro r cac loai hoa chat can phai ac biet chu y, bi v cac chat thai nguy hai b chay tran chi ph thu gom va x ly rat ton kem. V du, chat thai nguy hai b hap phu bi cac vat lieu de ngam nc nh rm ra, va dung dch b tham vao trong at th phai ao bi at e x ly. Luc nay cac chat thai nguy hai co the xem nh gom cac thanh phan chat long chay tran, chat hap phu (rm, ra), va ca at b o nhiem.

2.2 Thanh Phan Chat Thai Ran


Thanh phan cua chat thai ran bieu hien s ong gop va phan phoi cua cac phan rieng biet ma t o tao nen dong chat thai, thong thng c tnh bang phan tram theo khoi lng. Thong tin ve thanh phan chat thai ran ong vai tro rat quan trong trong viec anh gia va la chon nhng thiet b thch hp can thiet e x ly, cac qua trnh x ly cung nh viec hoach nh cac he thong, chng trnh va ke hoach quan ly chat thai ran.

Thong thng trong rac thai o th, rac thai t cac khu dan c va thng mai chiem t le cao nhat t 50-75%. Gia tr phan bo se thay oi tuy thuoc vao s m rong cac hoat ong xay dng, sa cha, s m rong cua cac dch vu o th. Thanh phan rieng biet cua chat thai ran thay oi theo v tr a ly, thi gian, mua trong nam, ieu kien kinh te va tuy thuoc vao thu nhap cua tng quoc gia.

Bang 2.1 Nguon goc cac loai chat thai

Nguon phat sinh

Ni phat sinh Cac dang chat thai ran

Khu dan c Khu thng mai C quan, cong s Cong trnh xay dng va pha huy Dch vu cong cong o th Nha may x ly chat thai o th

Ho gia nh, biet th, chung c. Nha kho, nha hang, ch, khach san, nha tro, cac tram sa cha va dch vu. Trng hoc, benh vien, van phong c quan chnh phu. Khu nha xay dng mi, sa cha nang cap m rong ng pho, cao oc, san nen xay dng. Hoat ong don rac ve sinh ng pho, cong vien, khu vui chi giai tr, bai tam. Nha may x ly nc cap, nc thai va cac qua trnh x ly chat

Thc pham d tha, giay, can nha, thuy tinh, can thiec, nhom. Giay, nha, thc pham tha, thuy tinh, kim loai, chat thai nguy hai. Giay, nha, thc pham tha, thuy tinh, kim loai, chat thai nguy hai. Gach, betong, thep, go, thach cao, bui,... Rac vn, canh cay cat ta, chat thai chung tai cac khu vui chi, giai tr. Bun, tro


Cong nghiep Nong nghiep

thai cong nghiep khac.Cong nghiep xay dng, che tao, cong nghiep nang, nhe, loc dau, hoa chat, nhiet ien. ong co, ong ruong, vn cay an qua, nong trai.

Chat thai do qua trnh che bien cong nghiep, phe lieu, va cac rac thai sinh hoat. Thc pham b thoi ra, san pham nong nghiep tha, rac, chat oc hai.

Nguon : Integrated Solid Waste Management, McGRAW-HILL 1993

2.2.1 S thay oi thanh phan chat thai ran trong tng lai

Nghien cu s thay oi thanh phan chat thai ran trong tng lai co y ngha rat quan trong trong viec hoach nh ke hoach quan ly chat thai ran, ong thi no cung quyet nh cac qui nh, d an va chng trnh quan ly cho cac c quan quan ly ( nh la s thay oi cac thiet b chuyen dung). Bon thanh phan co xu hng thay oi ln la: thc pham, giay va carton, rac vn, plastic.


Bang 2.2 S phan phoi cac thanh phan trong cac khu dan c o th cac nc co thu nhap thap, trung bnh va cao

Thanh phan (%)

Nc thu nhap thap

Nc thu nhap TB

Nc thu nhap cao

Chat Hu C Thc Pham Tha Giay Giay Carton Nha Vai Vun Cao Su Da Chat vo c Thuy tinh Can thiet Kim loai khac

40-85 1-10 - 1-5 1-5 1-5 - 1-10 1-5 1-40

20-65 8-30 2-6 2-10 1-4 - 1-10 1-5 1-30

6-30 20-45 5-15 2-8 2-6 0-2 10-20 4-12 2-8 1-4


Ghi chu:

- Nc co thu nhap thap < 750 $USD/nam (1990)

- Nc co thu nhap trung bnh: $750 < Thu nhap < $5000 USD/nam

- Nc co thu nhap cao > $5000 USD/nam

Nhn vao bang so lieu 2.2 ta co nhan xet: thc pham tha chiem t le phan tram trong lng rat cao tai cac nc co thu nhap thap. ieu nay co the do cac loai rau qua, thc an khong c s che trc khi a vao s dung.

2.2.2. Cach xac nh thanh phan rac thai o th tai hien trng

Thanh phan cua chat thai ran khong mang tnh chat ong nhat. Do o viec xac nh thanh phan cua cac chat thai khong phai la cong viec n gian. Cong viec kho khan nhat ma moi ngi quan tam trong viec thiet ke va van hanh he thong quan ly chat thai ran la d oan c thanh


phan cua chat thai trong hien tai va tng lai. Mot cach xac nh n gian nhat hien nay van ap dung la phng phap mot phan t.

Trnh t tien hanh nh sau:

- Mau chat thai ran ban au c lay t khu vc nghien cu co khoi lng khoang 100-250kg. o ong rac tai mot ni oc lap rieng biet, xao tron eu bang cach vun thanh ong hnh con nhieu lan. Khi mau a tron eu ong nhat chia hnh con lam 4 phan bang nhau.

- Ket hp 2 phan cheo nhau va tiep tuc tron eu thanh 1 ong hnh con. Tiep tuc thc hien bc tren cho en khi at c mau th nghiem co khoi lng khoang 20-30kg e phan tch thanh phan.

- Mau rac se c phan loai thu cong, bang tay. Moi thanh phan se c at vao moi khay tng ng. Sau o em can cac khay va ghi khoi lng cua cac thanh phan. e co so lieu cac thanh phan chnh xac, cac mau thu thap nen theo tng mua trong nam.

2.3. Khoi Lng Chat Thai Ran

2.3.1. Tam quan trong cua viec xac nh khoi lng chat thai ran

Xac nh khoi lng chat thai ran phat sinh va thu gom chat thai la mot trong nhng iem quan trong cua quan ly chat thai ran. Nhng so lieu ve tong khoi lng phat sinh cung nh khoi lng chat thai ran thu hoi e tai tuan hoan c s dung e:

- Hoach nh hoac anh gia ket qua cua chng trnh thu hoi, tai che, tuan hoan vat lieu.

- Thiet ke cac phng tien, thiet b van chuyen va x ly chat thai ran.

V du: Viec thiet ke cac xe chuyen dung e thu gom cac chat thai a c phan loai tai nguon phu thuoc vao khoi lng cua cac thanh phan chat thai rieng biet. Kch thc cua cac phng tien phu thuoc


vao lng chat thai thu gom cung nh s thay oi cua chung theo tng gi, tng ngay, hang tuan, hang thang. Tng t, kch thc cua bai rac cung phu thuoc vao lng chat thai ran con lai phai em o bo sau khi taisinh hoan toan.

2.3.2. Cac phng phap s dung e tnh toan khoi lng chat thai ran

Cac phng phap thng c s dung e c lng khoi lng chat thai ran la:

- Phng phap phan tch the tch khoi lng

- Phng phap em tai

- Phng phap can bang vat lieu

Cac phng phap nay khong tieu bieu cho tat ca cac trng hp ma phai ap dung no tuy thuoc vao nhng trng hp cu the.

Cac n v thng c s dung e bieu dien chat thai ran:

- Khu vc dan c va thng mai: Kg/(ngi.ngay em)

- Khu vc cong nghiep: n v khoi lng/n v san pham (kg/tan san pham)

n v trong lng/ca (kg/ca)

- Khu vc nong nghiep: Kg/tan san pham tho;

a. Phng phap khoi lng va the tch:

Trong phng phap nay khoi lng hoac the tch (hoac ca khoi lng va the tch) cua chat thai ran c xac nh e tnh toan khoi lng chat thai ran. Phng phap o the tch thng co o sai so cao.

V du: 1 m3 chat thai ran xop (khong nen) se co khoi lng nho hn 1 m3 chat thai ran c nen chat trong xe thu gom va cung co khoi lng khac so vi chat thai ran c nen rat chat bai chon lap. V vay neu o bang the tch th ket qua phai c bao cao kem theo


mc o nen chat cua chat thai hay la khoi lng rieng cua chat thai ran ieu kien nghien cu.

e tranh nham lan va ro rang, khoi lng chat thai ran phai c bieu dien bang phng phap xac nh khoi lng. Khoi lng la c s nghien cu chnh xac nhat bi v trong tai cua xe ch rac co the can trc tiep vi bat ky mc o nen chat nao o chat thai ran. Nhng so lieu ve khoi lng rat can thiet trong tnh toan van chuyen bi v

khoi lng chat thai ran van chuyen b han che bi mat o cho phep cua truc lo giao thong. Mac khac phng phap xac nh ca the tch va khoi lng rat quan trong trong tnh toan thiet ke cong suat bai chon lap rac, trong o cac so lieu c thu thap trong khoang thi gian dai bang cach can va o the tch xe thu gom.

b. Phng phap em tai

Trong phng phap nay so lng xe thu gom, ac iem va tnh chat cua chat thai tng ng (loai chat thai, the tch c lng) c ghi nhan trong suot mot khoang thi gian xac nh. Khoi lng chat thai

phat sinh trong thi gian khao sat (goi la khoi lng n v) se c tnh toan bang cach s dung cac so lieu thu thap tai khu vc nghien cu tren va cac so lieu a biet trc.


c. Phng phap can bang vat lieu

ay la phng phap cho ket qua chnh xac nhat, thc hien cho tng nguon phat sinh rieng le nh cac ho dan c, nha may cung nh cho khu cong nghiep va khu thng mai. Phng phap nay se cho nhng d lieu ang tin cay cho chng trnh quan ly. Cac bc thc hien can bang vat lieu thc hien nhh sau:

Bc 1: Hnh thanh mot hop gii han nghien cu. ay la mot bc quan trong bi v trong nhieu trng hp khi la chon gii han cua he thong phat sinh chat thai ran thch hp se a en cach tnh toan n gian.

Bc 2: Nhan dien tat ca cac hoat ong xay ra ben trong he thong nghien cu ma no anh hng en khoi lng chat thai ran.

Bc 3: Xac nh toc o phat sinh chat thai ran lien quan en cac hoat ong nhan dien bc 2.

Bc 4: S dung cac moi quan he toan hoc e xac nh chat thai ran phat sinh, thu gom va lu tr.

Can bang khoi lng vat lieu c bieu hien bang cac cong thc sau:

a. Dang tong quat:

b. Dang n gian

Tch luy = vao - ra - phat sinh

c. Bieu dien di dang toan hoc

Khoi lng vat lieu tch luy ben trong he thong (tch luy)

Khoi lng chat thai phat sinh ben trong he thong (chat thai ran + kh + nc thai)

Khoi lng vat lieu i vao he thong (nguyen + vat lieu)

Khoi lng vat lieu i ra khoi he thong (san pham)

= _ _


=

dtd Mvao - Mra - rw x t

Trong o:

::Toc o thay oi khoi lng vat lieu tch luy ben trong he thong nghien cu (kg/ngay, T/ngay)

Mvao : Tong cong khoi lng vat lieu i vao he thong nghien cu (kg/ngay)

Mra :Tong cong cac khoi lng vat lieu i ra he thong nghien cu (kg/ngay)

rw :Toc o phat sinh chat thai (kg/ngay)

t : Thi gian (ngay)

Trong mot so hoa trnh chuyen hoa sinh hoc , v du: san xuat phan compost khoi lng cua chat hu c se giam xuong, nen so hang rw se la gia tr am. Khi viet phng trnh can bang khoi lng th toc o phat sinh luon luon c viet la so hang dng.

Trong thc te, khho khan gap phai khi ap dung phng trnh can bang vat lieu la phai xac nh tat ca cac khoi lng vat lieu i vao va i ra he thong nghien cu.

Bai tap v du 2.1: c tnh lng chat thai phat sinh bnh quan tren au ngi t khu dan c da vao cac d lieu sau:

- Khu dan c gom 1.500 ho dan - Moi ho dan gom 6 nhan khau - Thi gian tien hanh giam sat la 7 ngay - Tong so xe ep rac: 9 - The tch xe ep rac: 15m3 - Tong so xe t nhan: 20 - The tch xe t nhan: 0,75m3

Giai ap:

dM/dt


1 Lap bang tnh:

Phng tien The tch (m3)

Khoi lng rieng (kg/m3)

Tong khoi lng (kg)

- Xe ep rac - Xe t

nhan Tong so, kg/tuan

15 0,75

300 100

40.500 1.500 42.000

2 Xac nh lng rac phat sinh tnh tren au ngi t khu dan c:

nngay/tua

tuan76500.1

/000.42

=

kg

= 0,67 kg/(ngi.ngay)

Bai tap v du 2.2: c tnh lng chat thai phat sinh da vao can bang vat lieu:

Mot nha may che bien o hop nhan 12 tan nguyen lieu tho e san xuat, 5 tan can e ng cac san pham che bien, 0,5 tan giay carton e lam thung ng cac san pham, va 0,3 tan cac loai nguyen lieu khac.

Trong so 12 tan nguyen lieu tho th lng san pham c che bien la 10 tan; 1,2 tan phe thai c s dung lam thc an gia suc va 0,8 tan c thai bo vao he thong x ly nc thai.

Trong so 5 tan can c nhap vao nha may th 4 tan c lu tr trong kho e s dung trong tng lai, phan con lai c s dung e ong hop; so lng can c s dung co 3% b hong va c tach rieng e tai che.

Lng giay carton nhap vao nha may c s dung het, trong so o co 5% b hong va c tach rieng e tai che.

Trong tong so cac loai vat lieu khac c nhap vao nha may th 25% c lu tr va s dung trong tng lai; 25% thai bo nh chat thai ran, 50% con lai la hon hp cac loai chat thai va trong so o th 35% c dung e tai che, phan con lai c xem nh chat thai ran em i thai bo.

Lng rac phat sinh hang


- Thiet lap s o can bang vat lieu da vao cac d kien tren? - Xac nh lng chat thai phat sinh khi san xuat 1 tan san pham?

Giai ap:

1. Nha may san xuat o hop: - 12 tan nguyen lieu tho - 5 tan can - 0,5 tan giay carton - 0,3 tan cac loai nguyen lieu khac. 2. Cac dong luan chuyen trong qua trnh san xuat:

a. 10 tan san pham c san xuat; 1,2 tan c lam thc an gia suc; 0,8 tan c thai vao he thong x ly nc thai.

b. 4 tan can c lu tr trong kho; 1 tan c s dung e ong hop; 3% trong so c s dung b hong va c dung e tai che.

c. 0,5 tan carton c s dung, 5% trong so o b hong va em i tai che.

d. 25% cac loai vat lieu c lu tr; 25% thai bo nh la chat thai ran; 50% con lai la hon hp cac loai chat thai va trong so o th 35% c dung e tai che, phan con lai c xem nh chat thai ran em i thai bo.


3. Xac nh so lng cac dong vat chat a. Chat thai phat sinh t nguyen lieu tho

+ Chat thai c s dung lam thuc an gia suc 1,2 tan + Chat thai c a vao he thong x ly nc thai: 12 - 10 -1.2

= 0,8 tan. b. Can

+ Can b hong va s dung e tai che: 0,03 (5-4) = 0,03 tan + S dung e ong hop: 1 - 0,03 = 0,97 tan

c. Giay carton + Giay b h hong va s dung e tai che: 0,05(0,5) = 0,025tan + Giay c s dung e ong thung: 0,5 - 0,025 = 0,475tan

d. Cac loai vat lieu khac + So lng lu tr: 0,25 x 0,3 = 0,075 tan + Giay c tai che: 0,5 x 0,35 x 0,3 = 0,053 tan + Hon hp chat thai: (0,3 -0,075 - 0,053) = 0,172 tan

e. Tong trong lng san pham: 10 + 0,97 + 0,475 = 11,445 tan f. Tong trong lng vat lieu lu tr: 4 + 0,075 = 4,075 tan

4 Chuan b bang can bang vat lieu a. Tong khoi lng cac vat lieu lu tr = Vat lieu vao - vat lieu ra - chat thai phat sinh b. Can bang vat lieu - Vat lieu lu tr = (4 + 0,075) tan = 4,075 tan - Vat lieu au vao = (12 + 5,0 + 0,5 + 0,3) tan = 17,8 tan - Vat lieu au ra = (10 + 1,2 + 0,97 + 0,03 + 0,475 + 0,025 + 0,053) =

12,753 tan - Chat thai phat sinh = (0,8 + 0,172) tan = 0,972 tan - Kiem tra can bang vat chat: 17,8 - 12,753 - 0,972 = 4,075 c. Thiet lap s o can bang vat lieu


5 Xac nh lng chat thai phat sinh khi san xuat 1 tan san pham

a. Vat lieu tai che = (1,2 + 0,03 + 0,025 + 0,053) tan/11,445 tan = 0,11

b. Hon hp chat thai ran = (0,8 + 0,172) tan/11,445 tan = 0,08

2.3.3. Khoi lng chat thai ran o th tai Thanh pho Ho Ch Minh

Khoi lng rac thong ke ngay cang tang, do lng rac thu gom c ngay cang triet e hn va viec s dung hanh hoa trong dan ngay cang tang. Theo so lieu khao sat nam 1998, lng rac Cong ty Moi trng o th khong thu gom c ma thai thang xuong kenh rach la 180.000 tan/nam. Nam 1999, Cong ty Dch vu Cong cong thu gom c 1.300.000 kg rac y te (gom chat thai lam sang, chat phong xa, chat thai hoa hoc) va 4.860.000 kg rac thai sinh hoat cac benh vien.

Khoi lng chat thai ran o th tai Thanh Pho Ho Ch Minh kho c thong ke chnh xac. Ch xac nh c lng rac sinh hoat thu gom do Cong ty Moi trng o th thc hien. Lng rac cua Thanh Pho Ho Ch Minh qua tng nam nh sau:

Bang 2.3 So lng rac thai Thanh Pho Ho Ch Minh

Nam Lng rac nam Phan tram tang khoi lng

tan/nam tan/ngay (%) Lng rac thong ke t nguon Cong ty Dch vu Cong cong Thanh Pho Ho Ch Minh 1983 181.802 498 100,00

12 tan nguyen lieu tho 5 tan can 0,5 tan giay carton 0,3 tan cac loai vat lieu khac

Vat chat lu tr trong he

thong 4,075 tan

11,445 tan san pham1,2 tan phe thai lam TAGS 0,03 tan can tai che 0,025 tan carton tai che 0,053 tan cac loai vat lieu khac tai che

0,8 tan chat thai a vao HTXLNT

0,172 tan hon hp chat thai ran


1984 180.484 494 99,27 1985 202.905 556 111,61 1986 202.483 555 111,37 1987 198.012 542 108,91 1988 236.982 649 130,35 1989 310.214 850 170,63 1990 390.610 1.070 170,30 1991 491.182 1.346 270,17 1992 616.406 1.812 339,05 1993 838.834 2.298 451,39 1994 1.005.417 2.755 553,02 1995 1.307.618 3.583 719,25 1996 1.405.331 3.850 773,00 1997 1.173.933 3.216 642,72 1998 1.186.628 3.251 652,70 D bao lng rac cua Thanh Pho Ho Ch Minh 2000 1.533.000 4.200 843 2005 1.825.000 5.000 1.003 2010 2.263.000 6.200 1.244 2015 2.738.000 7.500 1.506 2020 3.285.000 9.000 1.807

Nguon: Cong ty Moi trng o th TP.HCM (CITENCO), 2000

2.3 Cac yeu to anh hng en khoi lng chat thai ran

Cac yeu to anh hng en khoi lng chat thai ran bao gom :

9 Cac hoat ong tai sinh va giam thieu khoi lng chat thai ran tai nguon

9 Luat phap va thai o chap hanh luat phap cua ngi dan

9 Cac yeu to a ly t nhien

2.3.1 Anh hng cac hoat ong tai sinh va giam thieu khoi lng chat thai ran tai nguon:

Giam thieu chat thai tai nguon co the thc hien bang cach thiet ke, san xuat va ong goi cac san pham bang cac loai vat lieu hay bao b vi the tch nho nhat, ham lng oc to thap nhat, hay s dung cac


loai vat lieu co thi gian s dung lau dai hn. Sau ay la mot vai cach co the ap dung nham muc ch lam giam chat thai tai nguon:

9 Giam phan bao b khong can thiet hay tha

9 Thay the cac san pham ch s dung mot lan bang cac san pham co the tai s dung (v du cac loai dao, na, da co the tai s dung, cac loai thung cha co the s dung lai,)

9 S dung tiet kiem nguyen lieu (v du: giay photocopy 2 mat)

9 Gia tang cac vat lieu tai sinh cha trong cac san pham

9 Phat trien c cau, to chc khuyen khch cac nha san xuat thai ra t chat thai hn.

2.3.2 Anh hng cua luat phap va thai o cua cong chung

- Thai o, quan iem cua quan chung

Khoi lng chat thai ran phat sinh ra se giam ang ke neu ngi dan bang long va san sang thay oi y muon ca nhan, tap quan va cach song cua ho e duy tr va bao ve tai nguyen thien nhien ong thi giam ganh nang kinh te co lien quan en van e quan ly chat thai ran. Chng trnh giao duc thngxuyen la c s e dan en s thay oi thay o cua cong chung.

- Luat phap ban hanh

Yeu to quan trong nhat anh hng en s phat sinh va khoi lng chat thai ran la s ban hanh cac luat le, qui nh co lien quan en viec s dung cac vat lieu va o bo phe thai, V du nh: qui nh ve cac loai vat lieu lam thung cha va bao b, chnh nhng qui nh nay no khhuyen khch viec mua va s dung lai cac loai chai, lo cha

2.3.4 Anh hng cua cac yeu to a ly va t nhien

Cac yeu to t nhien anh hng en chat thai ran bao gom:

- V tr a ly - Mua trong nam


- Tan xuat thu gom chat thai - ac iem cua khu vc phuc vu

2.4 Tnh Chat Cua Chat Thai Ran

2.4.1 Tnh chat vat ly cua chat thai ran

Nhng tnh chat vat ly quan trong nhat cua chat thai ran o th la khoi lng rieng, o am, kch thc, s cap phoi hat, kha nang gi am tai thc a (hien trng) va o xop cua rac nen trong thanh phan chat thai ran.

a. Khoi lng rieng

Khoi lng rieng cua chat thai ran c nh ngha la trong lng cua mot n v vat chat tnh tren 1 m v the tch (kg/m3). Bi v chat thai ran co the nhhng trang thai nh: xop, cha trong cac thung cha container, khong nen, nen, nen khi bao cao gia tr khoi lng rieng phai chu thch trang thai cua cac mau rac mot cach ro rang. D lieu khoi lng rieng rat can thiet c s dung e c lng tong khoi lng va the tch rac can phai quan ly.

Khoi lng rieng thay oi phu thuoc vao nhieu yeu to nh: V tr a ly, mua trong nam, thi gian lu gi chat thai. Do o can phai than trong khi chon gia tr thiet ke. Khoi lng rieng cua mot chat thai o th bien oi t 180 400 kg/m3, ien hnh khoang 300 kg/m3.

Phng phap xac nh khoi lng rieng cua chat thai ran

Mau chat thai ran s dung e xac nh khoi lng rieng co the tch khoang 500 lt sau khi xao tron eu bang ky thuat mot phan t. Cac bc tien hanh nh sau:

1. o nhe mau chat thai ran vao thung th nghiem co the tch a biet ( tot nhat la thung co the tch 100 lt) cho en khi chat thai ay en mieng thung. 2. Nang thung len cach mat san khoang 30 cm va tha ri t do xuong 4 lan. 3. o nhe mau chat thai ran vao thung th nghiem e bu vao chat thai a len xuong.


4. Can va ghi khoi lng cua ca thung th nghiem va chat thai ran. 5. Tr khoi lng can c tren cho khoi lngcua ca thung th nghiem ta c khoi lng cua phan chat thai ran th nghiem. 6. Chia khoi lng tnh t bc tren cho the tch cua thung th nghiem ta c khoi lng cua phan chat thai ran th nghiem. 7. Lap lai th nghiem t nhat 2 lan e co gia tr khoi lng rieng trung bnh.

b. o am

o am cua chat thai ran c bieu dien bang 2 phng phap: Phng phap khoi lng t va phng phap khoi lng kho.

Phng phap khoi lng t o am trong mot mau c the hien nh la phan tram khoi lng t cua vat lieu.

Phng phap khoi lng kho o am trong mot mau c the hien nh phan tram khoi lng kho vat lieu.

Phng phap khoi lng t c s dung pho bien trong lnh vc quan ly chat thai ran bi v phng phap co the lay mau trc tiep ngoai thc a. o am theo phng phap khoi lng t c tnh nh sau:

M = ( w d )/ w x 100

Trong o: M la o am, % W la khoi lng mau luc lay tai hien trng, kg (g) D lakhoi lng mau lay sau khi say kho 105oC, kg

(g)


Bang 2.4 Thanh phan vat ly trong rac thai o th

Thanh phan Phan tram khoi lng o am % Chat hu c Thc pham tha Giay Giay carton Nha Vai vun Cao su Da Chat thai trong vn Go Chat vo c Thuy tinh Can thiec Nhom Vat lieu khac Bui, tro

9,0 34,0 6,0 7,0 2,0 0,5 0,5 18,5 2,0 8,0 6,0 0,5 3,0 3,0 100,0

70 6 5 2 10 2 10 60 20 2 3 2 3 8


Bai tap v du 2.3: c tnh o am cua 100 kg rac thai khu dan c o th khi biet cac phan tram khoi lng cua cac thanh phan, o am % Giai ap: 1. Thiet lap bang tnh da vao d lieu va cong thc 2-1 Thanh phan Phan tram khoi

lng o am % Khoi lng kho

(kg)


Chat hu c Thc pham tha Giay Giay carton Nha Vai vun Cao su Da Chat thai trong vn Go Chat vo c Thuy tinh Can thiec Nhom Vat lieu khac Bui, tro

9,0 34,0 6,0 7,0 2,0 0,5 0,5 18,5 2,0 8,0 6,0 0,5 3,0 3,0 100,0

70 6 5 2 10 2 10 60 20 2 3 2 3 8

2,7 32,0 5,7 6,9 1,8 0,5 0,4 7,4 1,6 7,8 5,8 0,5 2,9 2,8 78,8

2. Xac nh o am cua chat thai s dung cong thc 2-1

o am cua mau chat thai ran (%) = (100 78,8)/100 x 100 = 21,2%

c. Kch thc va cap phoi hat

Kch thc va cap phoi hat cua vat lieu thanh phan trong chat thai ran ong vai tro rat quan trong trong viec tnh toan va thiet ke cac phng tien c kh nh: thu hoi vat lieu, ac biet la s dung cac sang loc phan loai bang may hoac phan chia bang phng phap t tnh. Kch thc cua tng thanh phan chat thai co the xac nh bang mot hoac nhhieu phng phap nh sau:

SC = l (2-2) SC = (l + w)/2 (2-3) SC = (l + w + h)/3 (2-4) SC = ( l x w)1/2 (2-5) SC = (l x w x h)1/3 (2-6) Trong o: SC la kch thc cua cac thanh phan L la chieu dai, (mm) w la chieu rong, (mm) h la chieu cao, (mm)


Khi s dung cac phng phap khac nhau th ket qua se co s sai lech. Do o tuy thuoc vao hnh dang kch thc cua chat thai ma chung ta chon phng phap o lng cho phu hp.

d. Kha nang gi nc thc te

Kha nang gi nc thc te cua chat thai ran la toan bo lng nc ma no co the gi lai trong mau chat thai di tac dung keo xuong cua trong lc. Kha nang gi nc cua chat thai ran la mot ch tieu quan trong trong viec tnh toan xac nh lng nc ro r t bai rac. Nc i vao mau chat thai ran vt qua kha nang gi nc se thoat ra tao thanh nc ro r. Kha nang gi nc thc te thay oi phu thuoc vao ap lc nen va trang thai phan huy cua chat thai. Kha nang gi nc cua hon hp chat thai ran (khong nen) t cac khu dan c va thng mai dao ong trong khoang 50-60%.

e. o tham (tnh tham) cua chat thai a c nen

Tnh dan nc cua chat thai a c nen la mot tnh chat vat ly quan trong, no se chi phoi va ieu khien s di chuyen cua cac chat long (nc ro r, nuc ngam, nc tham) va cac kh ben trong bai rac. He so tham c tnh nh sau:

K = Cd2 = k

Trong o: K: he so tham C: hang so khong th nguyen d: kch thc trung bnh cua cac lo rong trong rac : khoi lng rieng cua nc : o nht van ong cua nc k: o tham rieng

So hang Cd2 c biet nh o tham rieng. o tham rieng k = Cd2 phu thuoc chu yeu vao tnh chat cua chat thai ran bao gom: s phan bo kch thc cac lo rong, be mat rieng, tnh goc canh, o rong. Gia tr ien hnh cho o tham rieng oi vi chat thai ran c nen trong


bai rac nam trong khoang 10-11 10-12 m2 theo phng ng va khoang 10-10 theo phng ngang.

2.4.2 Tnh chat hoa hoc cua chat thai ran

Cac thong tin ve thanh phan hoa hoc cua cac vat chat cau tao nen chat thai ran ong vai tro rat quan trong trong viec anh gia cac phng phap; la chon phng thc x ly va tai sinh chat thai. V du nh, kha nang ot chay vat lieu rac tuy thuoc vao thanh phan hoa hoc cua chat thai ran. Neu chat thai ran c s dung lam nhien lieu cho qua trnh ot th 4 tieu ch phan tch hoa hoc quan trong nhat la:

9 Phan tch gan ung s bo 9 iem nong chay cua tro 9 Phan tch cuoi cung (cac nhuyen to chnh) 9 Nhiet tr cua chat thai ran.

a. Phan tch s bo

Phan tch s bo oi vi cac thanh phan co the chay c trong chat thai ran bao gom cac th nghiem sau:

9 o am (lng nc mat i sau khi say 105oC trong 1 gi) 9 Chat de chay bay hi ( khoi lng mat i them vao khi em

mau chat thai ran a say 105oC trong 1 gi ot chay nhiet o 950oC trong lo nung kn)

9 Carbon co nh ( phan vat lieu con lai de chay sau khi loai bo cac chat bay hi)

9 Tro (khoi lng con lai sau khi ot chay lo h)


b. iem nong chay cua tro

iem nong chay cua tro c nh ngha la nhiet o ot chay chat thai e ro se hnh thanh mot khoi chat ran (goi la clinker) do s nay chay va ket tu. Nhiet o nong chay e hnh thanh clinker t chat thai ran trong khoang 2000 2200oF (1100 1200oC).

c. Phan tch cuoi cung cac thanh phan tao thanh chat thai ran

Phan tch cuoi cung cac thanh phan chat thai chu yeu xac nh phan tram (%) cua cac nguyen to C,H.O.N.S, va tro. Trong suot qua trnh ot chat thai ran se phat sinh cac hp chat Clor hoa nen phan tch cuoi cung thng bao gom phan tch xac nh cac halogen. Ket qua phan tch cuoi cung c s dung e mo ta cac thanh phan hoa hoc cua chat hu c trong chat thai ran. Ket qua phan tch con ong vai tro rat quan trong trong viec xac nh t so C/N cua chat thai co thch hp cho qua trnh chuyen hoa sinh hoc hay khong.

Bang 2.5 Gia tr phan tch cuoi cung cac thanh phan co trong rac thai o th

Phan tram khoi lng (khoi lng kho) Thanh phan Carbon Hydro Oxy Nit Sulfur Tro Chat hu c Thc pham tha Giay Giay carton Nha Vai vun Cao su Da Chat thai trong vn Go Chat vo c Thuy tinh Kim loai Bui, tro

48,0 43,5 44,0 60,0 55,0 78,0 60,0 47,8 49,5 0,5 4,5 26,3

6,4 6,0 5,9 7,2 6,6 10,0 8,0 6,0 6,0 0,1 0,6 3,0

37,6 44,0 44,6 22,8 31,2 - 11,6 38,0 42,7 0,4 4,3 2,0

2,6 0,3 0,3 - 4,6 2,0 10,0 3,4 0,2 < 0,1 < 0,1 0,5

0,4 0,2 0,2 - 0,15 - 0,4 0,3 0,2 - - 0,2

5,0 6,0 5,0 10,0 2,5 10,0 10,0 4,5 1,5 98,9 90,5 68,0

Bai tap v du: Xac nh thanh phan hoa hoc cua mot mau rac o th da vao cac thong tin nh sau: Khoi lng t, khoi lng kho, va khoi lng cua cac nguyen to hoa hoc cha trong mau chat thai da vao bang so lieu 2.4 va 2.5.


Thanh phan hoa hoc, g Thanh

phan KL t KL kho

C H O N S Tro Thc pham

Giay Giay carton

Nha Vai vun Cao su

Da Rac vn

Go

9,0 34,0 6,0 7,0 2,0 0,5 0,5 18,5 2,0

2,7 32,0 5,7 6,9 1,8 0,5 0,4 6,5 1,6

1,30 13,922,51 4,14 0,99 039 0,24 3,11 0,79

0,17 1,92 0,34 0,50 0,12 0,05 0,03 0,39 0,10

1,02 14,082,54 1,57 0,56

- 0,05 2,47 0,68

0,07 0,10 0,02

- 0,08 0,01 0,04 0,22

-

0,01 0,06 0,01

- - - -

0,02 -

0,14 1,92 0,28 0,69 0,05 0,05 0,04 0,29 0,02

Tong cong 79,5 58,1 27,39 3,62 22,97 0,54 0,10 3,48

o am: 21.4 g (79.5 58.1 g)

Giai ap:

1. Chuan b bang tom tat phan tram phan phoi cua cac nguyen to hoa hoc vi thanh phan co nc va khong co nc trong chat thai

Khoi lng, g Thanh phan Khong co nc Co nc

C H O N S

Tro

27,39 3,62 22,97 0,54 0,10 3,48

27,39 6,00 41,99 0,54 0,10 3,48

2. Tnh so mol cua cac nguyen to bo qua phan tro

So mol Thanh phan

Khoi lng nguyen t

g/mol Khong co nc Co nc

C H O N S

12,01 1,01 16,00 14,01 32,07

2,280 3,584 1,436 0,038 0,003

2,280 5,940 2,624 0,038 0,003


3. Xac nh cong thc hoa hoc cua CTR co va khong co S, co va khong co nc. Xac nh t so mol.

T so mol (N =1) T so mol (S = 1) Thanh phan Khong co

nc Co nc Khong co

nc Co nc

C H O N S

60,0 94,3 37,8 1,0 0,1

60,0 156,3 69,1 1,0 0,1

760,0 1194,7 478,7 12,7 1,0

760,0 1980,0 874,7 12,7 1,0

Cong hc hoa hoc khong co s hien dien cua S la:

9 Khong co nc: C60.0H94. 3O37.8N

9 Co nc: C60.0H156.3O69.1N

Cong hc hoa hoc co s hien dien cua S la:

9 Khong co nc: C760.0H 1194.7O478.7N12.7S

9 Co nc: C760.0H1980.0O874.7N12.7S

Ghi chu: Cong thc hoa hoc sau khi tnh xong ket qua th tien hanh lam tron so.

d. Nhiet tr cua cac thanh phan chat thai ran

Nhiet tr cua cac thanh phan hu c trong thanh phan chat thai ran o th co the c xac nh bang mot trong cac cach sau:

9 S dung noi hay lo chng cat qui mo ln

9 S dung bnh o nhiet tr trong phong th nghiem

9 Bang cach tnh toan neu thanh phan cua cac nguyen to hoahoc c xac nh

Do kho khan trong viec trang b lo chng cat qui mo ln, nen hau het cac so lieu ve nhiet tr cua cac thanh phan hu c trong chat thai ran o th eu da tren ket qua th nghiem s dung bnh o nhiet tr trong phong th nghiem.


Bai tap v du 2.5: c tnh gia tr cua rac thai khhu dan c o th da vao cac so lieu ve phan tram khoi lng va gia tr nhiet tr cua tng thanh phan chat thai.

Giai ap:

1. Xac nh gia tr nhhiet tr tong cong da vao ac tnh thanh phan chat thai.

Thanh phan Phan tram khoi lng, lb

Nhiet tr Btu/lb

Tong nhiet tr Btu

Chat hu c Thc pham tha Giay Giay carton Nha Vai vun Cao su Da Chat thai trong vn Go Chat vo c Thuy tinh Can thiec Nhom Kim loai khac Bui, tro

9,0 34,0 6,0 7,0 2,0 0,5 0,5 18,5 2,0

8,0 6,0 0,5 3,0 3,0

100,0

2.000 7.200 7.000 14.000 7.500 10.000 7.500 2.800 8.000

60 300 -

300 3.000

18.000 244.800 42.000 98.000 15.000 5.000 3.750 51.800 16.000

480

1.800

900 9.000

506.530

2. Xac nh nhiet tr cua chat thai

Neu gia tr Btu khong co san, co the tnh gia tr gan ung bang cong thc Dulong cai tien:

Btu/lb = 145C + 610 (H2 1/8 O2) + 40S + 10N

Trong o: C: % khoi lng cua carbon

Nhiet tr cua chat thai =


H: % khoi lng cua hydro O2: % khoi lng cua oxy S: % khoi lng cua Sulfua N: % khoi lng cua N

Bai tap v du 2.6: c tnh gia tr nhiet tr cua mot loai chat thai ien hnh khu dan c da vao cong thc hoa hoc. Gia s cong thc hoa hoc la C760H1980O875N13S

Giai ap:

1. Xac nh phan ttram phan phoi theo khoi lng cua tng nguyen to

Thanh phan

So lng nguyen t /

mol

Khoi lng nguyen t

Khoi lng phan phoi tng nguyen

to %

C H O N S

Tong cong

760 1980 875 12 1

12 1 16 14 32

9.120 1.980 14.000 182 32

25.314

36,03 7,82 55,30 0,72 0,13 100

2. Xac nh gia tr nhiet tr cua chat thai s dung phng trnh 2-8

Btu/lb = 145(36,0) + 610(7,8 55,3/8) + 40(0,1) + 10(0,7)

Btu.lb = 3204 Kcal/kg

2.2.2 Tnh chat sinh hoc cua chat thai ran

Cac thanh phan hu c (khong ke cac thanh phan nh plastic, cao su, da) cua hau het chat thai ran co the c phanloai ve phng dien sinh hoc nh sau:

9 Cac phan t co the hoa tan trong nc nh: ng, tinh bot, amino acid va nhieu acid hu c

9 Ban cellulose: cac san pham ngng tu cua 2 ng 5 va 6 carbon


9 Cellulose: san pham ngng tu cua ng glucose 6 carbon 9 Dau, m, va sap: la nhng ester cua alcohols va acid beo mach

dai 9 Lignin: mot polymer cha cac vong thm vi nhom methoxyl (-

OCH3) 9 Lignocelluloza: hp chat do lignin va celluloza ket hp vi nhau 9 Protein: chat tao thanh t s ket hp chuoi cac amino acid

Tnh chat quan trong nhat trong thanh phan hu c cua phan chat thai ran o th la hau het cac thannh phan hu c co the c chuyen hoa sinh hoc thanh kh, cac chat vo c va cac chat tr khac. S tao mui hoi va phat sinh ruoi cung lien quan en tnh de phan huy cua cac vat lieu hu c trong chat thai ran o th chang han nh rac thc pham.


a. Kha nang phan huy sinh hoc cua cac thanh phan hu c trong chat thai ran

Ham lng chat ran bay hi (VS), xac nh bang cach ot chay chat thai ran nhiet o 550oC, thng c s dung e anh gia kha nang phan huy sinh hoc cua phan hu c trong chat thai ran. Tuy nhien s dung gia tr VS e mo ta kha nang phan huy sinh hoc cua phan hu c trong chat thai ran th khong ung bi v mot vai thanh phan hu c cua chat thai ran rat de bay hi nhng lai kem kha nang phan huy sinh hoc nh la giay in. Thay vao o ham lng lignin cua chat thai ran co the c s dung e c lng t le phan de phan huy sinh hoc cua chat thai ran, va c tnh toan bang cong thc sau:

BF = 0,83 0,028LC

Trong o: BF : t le phan huy sinh hoc bieu dien tren c s VS 0,83 va 0,028 la hang so thc nghiem LC: ham lng lignin cua VS bieu dien bang % khoi lng kho

Cac chat thai ran vi ham lng lignin cao nh: giay in co kha nang phan huy sinh hoc kem hn ang ke so vi cac chat thai hu c khac trong chat thai ran o th. Trong thc te cac thanh phan hu c trong chat thai ran thng c phan loai theo thanh phan phan huy cham va phan huy nhanh.

b. S phat sinh mui hoi

Mui hoi co the phat sinh khi chat thai ran c lu gi trong khoang thi gian dai mot ni gia thu gom, tram trung chuyen, va ni chon lap. S phat sinh mui tai ni lu tr co y ngha rat ln, khi tai ni o co kh hau nong am. Noi mot cach c ban la s hnh thanh cua mui hoi la ket qua cua qua trnh phan huy yem kh vi s phan huy cac thanh phan hp chat hu c tm thay trong rac o th. V du, trong ieu kien yem kh (kh), sunphat SO42- co the phan huy thanh sunfur S2-, va ket qua la S2- se ket hp vi H2 tao thanh hp chat co mui


trng thoi la H2S. S hnh thanh H2S la do ket qua cua 2 chuoi phan ng hoa hoc.

2CH3CHOHCOOH + SO42- 2CH3COOH + S2- + 2 H2O + 2CO2 (2-10)

Lactate Sulfate Acid Acetic Sulfide ion 4H2 + SO42- S2- + 4H2O S2- + 2H+ H2S


Ion sulfide (S2-) co the cung ket hp vi muoi kim loai nh sat, tao thanh cac sulfide kim loai.

S2- + Fe2+ FeS

Nc rac tai bai rac co mau en la do ket qua hnh thanh cac muoi sulfide trong ieu kien yem kh. Do o neu khong co s hnh thanh cac muoi sulfide th viec hnh thaanh mui hoi tai bai chon lap la mot van e o nhiem moi trng co tnh chat nghiem trong.

CH3SCH2CH2CH(NH2)COOH CH3SH + CH3CH2CH2(NH2)COOH

Methionine Metyl mercaptan Aminobutyric acid

CH3SH + H2O CH4OH + H2O

c. S phat trien cua ruoi

Trong thi iem mua he hay la trong khu vc kh hau nong am, s nhan giong va sinh san cua ruoi la van e quan trong can quan tam tai ni lu tr chat thai ran. Ruoi co the phat trien trong thi gian 2 tuan sau khi trng c sinh ra. i song cua ruoi nhan t khi con trong trng cho en khi trng thanh co the c mo ta nh sau:

9 Trng phat trien 8-12 gi 9 Giai oan I cua au trung (gioi) 20 gi 9 Giai oan II cua au trung 24 gi 9 Giai oan III cua au trung 3 ngay 9 Giai oan nhong 4-5 ngay 9 Tong cong 9-11 ngay

Giai oan phat trien cua au trung trong cac thung cha rac ong vai tro rat quan trong va chiem khoang 5 ngay trong s phat trien cua ruoi. e han che s phat trien cua ruoi th cac thung lu tr rac nen o bo e thunng rong trong thi gian nay e han che s di chuyen cua cac loai au trung.

2.4.4 S bien oi ac tnh ly, hoa, va sinh hoc cua chat thai ran

Chat thai ran co the bien oi bang cac phng phap ly, hoa, va sinh hoc. Khi thc hien hoa trnh bien oi th muc ch quan trong nhat la

+2H


phai co hieu qua bi v s bien oi cac ac tnh cua chat thai ran co anh hng rat ln en ke hoach phat trien chng trnh quan ly chat thai ran tong hp.

a. Bien oi vat ly: Bao gom cac phng phap: tach loai cac thanh phan; giam the tch bang c kh; giam kch thc bang c kh. Bien oi vat ly khong anh hng en s thay oi gia cac pha (v du t ran sang long).

b. Bien oi hoa hoc: Bien oi hoa hoc anh hng en s bien oi gia cac pha (v du: ran sang long hoac ran sang kh). Muc ch la lam giam the tch va thu hoi cac san pham bien oi. Bao gom cac phng phap: oy (oxy hoa hoa hoc); va s nhiet phan. Cac phng phap nay xem nh la qua trnh nhiet.

c. Bien oi sinh hoc: Bien oi sinh hoc cac thanh phan hp chat hu c trong chat thai muc ch la lam giam the tch va trong lng cua cac vat chat, san xuat phan compost, cac chat mun lam on nh at, kh metan. Cac loai vi khhuan, nam, va men ong vai tro rat quan trong trong viec bien oi cac hp chat hu c. Qua trnh bien oi nay xay ra trong ieu kien hieu kh va yem kh tuy thuoc vao s hien dien cua oxy. Bao gom 2 phng phap: Phan huy hieu kh va phan huy k kh.

Bang 2.6 Cac qua trnh bien oi ap dung trong quan ly chat thai ran

Qua trnh bien oi

Phng phap bien oi Bien oi hoac thay oi c ban san pham

Ly hoc Tach loai theo thanh phan

Giam the tch Giam kch thc

Hoa hoc ot S nhiet phan

Tach loai bang tay hoac may S dung lc hoac ap suat S dung lc cat, nghien hoac xay nho Oxy hoa bang nhiet

Cac thanh phan trong hon hp chat thai o th Giam the tch ban au Bien oi hnh dang ban au CO2, SO2, sp oxy hoa khac, tro


Kh hoa Sinh hoc Hieu kh compost K kh pha huy K kh compost

S chng cat, phan huy ot thieu kh Bien oi sinh hoc hieu kh Bien oi sinh hoc k kh Bien oi sinh hoc k kh

Kh gom hon hp kh, can dau va than Phan compost CH4, CO, SP phan huy con lai mun hoac bun CH4, CO2, rac con lai

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