NGHIEN CAU AP DUNG KIEM TOAN CHAT THAI TAI XI NGHIEP CHE BIEN THUY DAC SAN XUAT KHAU HANOI

N g u y e n Thi Ha, B u i Th i L u a n

Khoa Moi trudng, TrUdng DHKHTN,

BHQGHN

TOM TAT

Kiem toan moi trUdng noi chung va Kiem toan chat thai cong nghiep ndi rieng la mot cong cu quan ly mdi dUdc ap dung d nUdc ta trong mot vai nam gan day. Mac du day la cong cu mdi nhung qua cac ket qua ap dung kiem toan tai nhieu cd sd san xuat cho thay cong cu nay mang lai Idi ich kbong nbd ca ve moi trUdng va hieu qua kinh te. Trong cong trinb nay chung toi tien hanh nghien ciiu ap dung kiem toan chat thai tai xi nghiep Che bien Tbuy dac san xuat khau Ha Noi (F37) vdi muc dich ap dung cong cu kiem toan vao viec giam tbieu chat thai tai xi nghiep nb im tim ra nhiing khau ton that nUdc, nguyen lieu de tix do diia ra nhiing phUdng an cho'ng that thoat, giam tbieu chat thai, tang hieu qua cua qua trinb san xuat, dong tbdi cai thien chat lUdng moi trUdng cho xi nghiep va nang cao hieu qua kinh te trong san xuat kinh doanh. Cac noi dung cu the dudi day se dUdc nghien ciiu:

1) Tim hieu day chuyen cong nghe che bien, miJtc do tieu thu nUdc, nguyen lieu va cac chat thai phat sinh.

2) Tinb toan can b^ng nUdc, can b^ng chat thai r^n.

3) Xac dinh cac khau gay lang phi nUdc va cac nguon gay 6 nhiem moi trUdng.

4) Xem xet, danh gia cac phUdng an xii ly, giam tbieu lang phi nUdc cua xi nghiep,

63

5) De xuat cac giai phap c6 tinb kha thi nh^m tiet kiem nUdc, giam CTR, xii ly nUdc thai nh^m cai thien moi trUdng va tang cUdng hieu qua kinh te cho xi nghiep.

I. KIEM TOAN CHAT THAI CONG NGHIEP

Kiem toan chat thai la mot loai hinh cua KTMT la cong cu c6 gia tri de cac doanh nghiep kiem tra lai kha nang tuan thu cac tieu chuan moi trUdng, giam cac vi pham ve moi trUdng, giam thieu chat thai va tang cUdng kha nang quan ly moi trUdng.

Kiem toan chat thai la budc d^u tien de giam chat thai va ciing lam giam 6 nhiem moi trUdng. N6 la qua trinb kiem tra khach quan cac qua trinh san xuat va chat thai nh4m muc dich giam nguon thai tang s\i dung lai boac loai bo boan toan chat thai. Qua kiem toan cac phUdng an giam thieu chat thai dUdc nhan dang, dUdc danh gia, dUdc lUa ebon, dUdc thUc hien va dUdc giam sat.

Viec thUc h i e n kiem toan giam thieu chat thai cho xi nghiep F37 dUdc thUc hien theo hudng d^n gom 9 bUdc theo 3 giai doan [Trinb Thi Thanh, Nguyen Thi Ha, 2003]. Nghien ciiu dUdc thUc hien tai xi nghiep sau hdn 4 thang khao sat hien trang va tinb toan thUc hien cac budc kiem toan vdi trong tam kiem toan la day chuyen che bien torn va 2 chat thai chinh la nUdc thai va chat thai r^n.

II. CAC VAN Dfi MOI T R U 6 N G CUA NGANH C H ^ BIEN THUY SAN

Qua trinb san xuat che bien thuy san c6 anh hudng Idn tdi moi trUdng dac biet la moi trUdng nUdc va moi trUdng khong khi.

Kbong kbi trong cac khu vUc san xu^'t va khong khi xung quanh thUdng cbiu tac dong cua cac yeu to gay 6 nbiim nhu mui hoi thoi, mui tanh, khi HgS, boa chat nhu clo, mercaptan, ure...do qua trinh phan buy cac chat c6 trong nUdc thai va phe thai r4n thai trong qua trinh san xuat. Ngoai ra trong qua trinh san xuat che bien con su( dung pho bien cac thiet bi lanb de duy tri boat dong cua cac may nen lanh va day CO the la nguon gay 6 nbiim moi trUdng khong khi (khi NHg, freon,...)

64

Khdi lUdng chat thai ran thai bd trong qua trinh san xuat la rat Idn bao gom cac thanh phan nhU: dau; v6 tom; noi tang cac loai ca, mUc; mai mUc; ong mUc; xUdng. vay, vay ca...Day la cac chat giau chat hiiu cd de p h t o buy sinh hoc c6 tiem nang gay 6 nhiem moi trUdng neu khong cd bien phap thu gom, xcL \i kip tbdi se anh hUdng dang ke den moi trUdng va sxic khoe con ngUdi.

Van de dang quan tam hdn ca trong san xuat che bien thuy san la van de suf dung nUdc va nUdc thai. Qua trinh che bien can mot lUdng nUdc tUdng do'i Idn. Nudc thai che bien thuy san cd ham lUdng cac chat ran, cac chat huEu cd de phan buy sinh hoc cao. Cac chat nay ton tai trong nUdc d dang keo, dang boa tan, dang phan tan min lam cho nude thai c6 mau va do due Idn. Qua trinh phan buy cac chat nay trong nUdc tao ra cac miii khd chiu va doc hai. Ngoai ra nUdc thai con c6 mat cac boa chat khii trung nhU clo, javen; cac chat tay riia, chat boat dong be mat dung trong hoat dong ve sinh nha xUdng.

Hien nay van de moi trUdng mdi dUdc quan tam trong eac cd sd che bien c6 quy mo Idn. Con lai trong hau bet cac cd sd che bien c6 quy mo viia va nhd van de moi trUdng con it dUdc quan tam.

III. KET QUA KIEM TOAN CHAT THAI

Nhin chung moi trUdng trong xi nghiep luon dUdc giiJ thong thoang va sach se. Trong khu vUc san xuat che bien van de moi trUdng cung da dUdc quan tam. Xi nghiep c6 ba cong nhan chuyen quet don va thu gom do chat thai ran (khu vUc xung quanh xi nghiep) va chat thai ran san xuat. Cong tac ve sinh moi trUdng da dUdc xi nghiep tbUc hien mot each nghiem tuc.

3.1 . N g u y e n n h i e n l i e u , nvtdc v a h o a c h a t sxi d u n g

Nguyen, nhien lieu

Nguyen lieu chinh ciia xi nghiep la tom, mUc, ca cac loai dUdc thu mua tiif cac vung khac nhau nhU: Quang Ninb, Hai Phong, Thai Binh, Thanh Hoa, Nghe An, Ha Tinb. Trung binh moi nam xi nghiep thu

65

mua khoang 450 tan nguyen lieu, lUdng nguyen lieu mdi loai thay doi theo tiing nam va phu thuoc vao tbdi tiet. Nguyen lieu thu mua trong nam 2002 dUdc chi ra trong bang sau.

Bang 1 - Li^dng nguyen lieu thu mua trong nam 2002

STT

1

2

3

4

5

6

Nguyen, nh i en lieu sijf dung

Tom cac loai (Tan/nam)

Muc (Tan/nam)

Ca cac loai (Tan/nam)

Tong nguyen lieu (Tan/nam)

Dien (kWh)

Dau DO (Lit)

So litdng

302,7

171,9

23,7

498,3

700 000

400

[Nguon: Phong Ke toan Tai chinh cua xi nghiep F. 37]

Hod chat

Hoa chat svL dung chu yeu la chlorin vdi khoi lUdng khoang 30 kg/ nam. Chlorin diing kbit trung nguyen vat lieu, dung cu thiet bi, tiep xuc vdi san pham, ngan chan su phat trien cua vi sinh vat va khong lam anh hudng tdi chat lUdng san pham. Ngoai chlorin xi nghiep con dung H2O2 de ngam va tay tr^ng mUc tuy nhien lUdng dung khong dang ke.

Ni/dc

Nguon nude sii dung cua xi nghiep la nUdc gieng khoan da qua he thong xd li bao gom: Nude'diing cho sinh hoat, nUdc dung cho san xuat da, nUdc diing ve sinh nha xudng va nUdc dung cho cac cong doan san xuat.

Hien nay trong tat ca cac cong doan san xuat cua xi nghiep deu chua lap dong ho do nudc do d6 viec tinb toan lUdng nUdc sd dung chi mang tinb chat tUdng do'i. Xi nghiep c6 hai may bdm:

66

* May bdm cong suat 30 m /b lam viec trung binh 4h/ngay. * May bdm cong suat 12m /h lam viec trung binh 8h/ ngay.

Tong ludng nUdc bdm trong mot ngay la: 30 x 4 + 12 x 8 = 216 (m'^), tinb trung binh trong mot nam tong so'ngay lam viec cua xi nghiep la 200 ngay do do lUdng nude khai thac trong mot nam c6 the Udc tinb nhu d bang 2.

Bang 2- Li^tfng nUdc suf dung cho cac muc dich khac nhau t rong Xi nghiep

STT

1'

2

3

4

5

Loai nvtdc svt dung

Nude sinh boat

Nude san xuat da

Nude ve sinh cong nghiep

Nude cho cac cong doan san xuat

Tong

hxidng (m^/nam)

3120

1000

1348

25732

31200

3.2. Qui t r i n h c o n g n g h e c h e b i e n

Cac loai san pham torn, mUc, ca dong lanh deu dUdc che bien theo

quy trinh chung nbu d hinh 1. Tuy nhien, tuy theo loai san pham ma

cd the bdt di mot boac mot so* cong doan.

Tren cd sd tbdi gian nghien cdu tai xi nghiep, quy trinh che bien

torn thit dong lanh dUdc lUa chon la doi tUdng cho kiem toan vdi t r o n g

t a m k iem toan la moi trUdng nUdc bao gom cac noi dung sau: (1) Tinb

toan lUdng nUdc thUc te sxi dung; (2) Tinb toan can b§ng nUdc cho qui

trinh che bien tom de xac dinh cac khau gay that thoat nUdc; (3) Tinb

can b^ng chat thai vkn de xac dinh lUdng chat thai di vao dong thai;

(4) Tinb toan chi phi cho viec sii dung nUdc vUdt dinh mvic va dUa ra

cac bien phap n h i m tiet kiem nUdc cho xi nghiep; (5) De xuat giai

phap tiet kiem nUdc sii dung, giam thieu lUdng nUdc thai va xii ly nUdc

thai d cong doan cd dac tinb 6 nhiem cao.

67

Nudc da—>

Nudc da—•

Nude—•

D a _ >

Nude—•

D a - >

Nudc—^

Nudc—•

Th i ing -> carton

Nang lUdng—^

Ngu3'en lieu: Tom. mUc, ca...

i Tiep nhan, rda nguyen lieu,

bao quan.

1 Xiily

+ Riia Ian 2

1 Nhat tap chat

+ Rua Ian 3

1 Phan cd hang

i Riia Ian 4

i De rao nUdc, can, xep khuon

i Chd cap dong

i Tach khuon, ma bang,

dong tui PE

i May do kim loai

i Bao goi, dong tbung carton

i Bao quan kho lanh

— • N u d c thai

. Nudc thai, CTR

— • N u d c thai

Nudc thai, nhat tap chat

— • N u d e thai

— • N u d c thai

Nude thai, bao bi thai bd

^ Thiing phe thai

Hinh 1: Quy trinh cong nghe che bien

68

3.3 T i n h t o a n c a n b^ng nxidc va c h a t t h a i r a n

Binh mite ni/dc sti dung

Nham dap ling cac yeu cau ve ve sinh thUc pham, hien nay xi nghiep dang tien hanh san xuat theo mot so'tieu chuan kiem soat chat lUdng thuy san nhu GMP (He thong san xuat to't), HACCP (He thong phan tich rui ro va kiem soat gia tri tdi ban). De thUc hien tot cac tieu chuan tren dong tbdi nham giam cbi phi cho san xuat xi nghiep da dUa ra dinh mute nUdc sii dung cho nguyen lieu torn nhU sau;

Tom cac loai: 20 m^/TNL; Dinh miic da sii dung la 2 tan da/TNL

Tuy nhien, dinh miic xi nghiep dUa ra mdi chi dUdc thUc hien trong mot so' cong doan con trong thUc te lUdng nUde sii dung cua xi nghiep cao hdn dinh miic r^'t nhieu.

Can bang nitdc trong qud trinh san xuat tom

* Ludng nude sii dung trong cac cong doan san xuat:

Ta so' lieu bang 2, ta thay rang lUdng nUdc dung trong cac cong

doan san xuat la 25.732m2/nam. Theo bo phan ki thuat cua xi nghiep

ti le sii dung nUdc so sanh vdi dinh mdc de san xu^'t 1 TNL torn, mUc,

ca t rong thUc te tUdng iing la 2: 3: 3. Tii ti le nay va can cii vao

lUdng nguyen lieu thu mua moi loai nam 2002 c6 tong so' phan

nUdc sii dung la:

(302,5 tan tom x 2) + (171,9 tan mUc X 3) + (23,7 tan ca x 3) = 1192,2 (phan).

LUdng nUdc dung cho qui trinh che bien tom:

Wt5^ = 25732 : 1191,8 x 2 ^ 43,18 (m^)

* LUdng nUdc diing de ve sinh nha xudng (nam 2002):

LUdng nUdc dung de ve sinh nha xUdng:

1348m3 : 498,3 TNL = 2.7 (mWNL)

Vi vay, tong lUdng nUdc sii dung (gom ve smh nha xUdng) cho 1 TNL

(tom) la: 43,18 + 2,7 = 45,88 m^

69

Nhu vay lUdng nUdc sii dung vUdt dinh miic tinh tren 1 TNL doi vdi

nguyen heu dau vao la tom rat Idn (gap hdn 2-3 Ian), tUdng iing la:

45,88 - 20 = 25,88 m^/TNL.

Nhu vay tong lUdng nUdc sd dung vUdt dinh mdc nam 2002 (W^ j ) la:

WvDM(tdm) = 25,88m3/TNL x 302,5TNL/nam = 7828,7m3/nam

Can b^ng nUde dUdc t inh toan cho tufng cong doan, cac k e t qua

dUdc cbi ra d bang 3.

Bang 3: Lifdng nUdc suf d u n g va nifdc t h a i t r o n g cac cong doan san x u a t

TT

1

2

3

4

5

6

7

8

Cong d o a n che b ien

Tiep nhan nguyen

lieu, riia, bao quan

Sd che nguyen lieu

Rijta Ian 2, nhat tap chat

Phan cd bang

Ru[a Ian 3, de rao, can

Xep khuon

Tach khuon, ma bang,

dong PE

Tong

Dau

Nxidc (m /TNL)

3,04

33,6

1,5

2,1

0,123

1,717

42,08

vao

Da (Tan/TNL)

0,5

1

0,25

0,25

2,0

Nvidc t h a i

(m^/TNL)

3,54+ Aw

34,6+ Aw

1,75+Aw

0,25± Aw

2,l±Aw

1,717+Aw

43,975±Aw

(*)Ghi ehu:

A^ - LUdng nLf6c chenh lech do that thoat (bay hoi, ng^'m,...) hoac do con lai tii

cong doan trxidc

^WT{*)" ^^^^ Lutdng nUdc chenh lech do that thoat (bay hdi, ngam,...) hoac do con lai tCt cong doan trU6c

70

Trong cac cong doan eiia qui tr inh che bien tom chi c6 cong doan xep khuon la nUdc dUdc di vao san pham con lai ta t ca cac cong doan khac nUdc va nUde da tan deu theo eac mang thoat nUdc thai ra ngoai. Ngoai ra trong qua trinh san xuat con mot lUdng nUde bi tha t thoat do bay hdi, do tham vao san nha va eac dung eu thiet bi. Do d6 qua so lieu tong ket d bang 3. tren thUe te lUdng nudc thai ra la: Wj ^ = 43,795± AWT(*) (m'VTNL).

Dinb mde da sU dung cua xi ngbiep vdi torn la: 2 tan/TNL. NhU vay CO the thay lUdng da sii dung trong cae eong doan la phii hdp vdi dinh mile dat ra.

TU cac ket qua tinh toan tren ta c6 the dUa ra sd do can bang nUdc nhu trong hinh 2.

Nguyen nhan dan den sii dung ni/dc vUOt dinh mdc

Cac ket qua tinh toan can bang nUdc ket hdp vdi qua trinh khao sat eac dieu kien san xuat trong xi nghiep. nguyen nhan dan den lUdng nUde sii dung vUdt hdn nhieu so vdi dinh mUc la do:

- Nudc dUdc sii dung ehUa hdp ly cho cong doan sd che nguyen lieu. Trong cong doan nay torn dUde boe v6, bd dau, rut ruot dUdi vdi nUdc ehay nhe. Tuy nhien qua thuc te nhan thay khong phai luc nao cong nhan ciing de tay dUdi voi nUde. NhU vay se c6 nln2ng khoang tbdi gian nUdc ehay ma khong dUdc sii dung do do se gay lang phi rat nhieu nUdc.

- Xi nghiep mdi ap dung dinh miic nUdc sii dung trong mot so eong doan nhu riia nguyen lieu, ban thanh pham, xep khuon. Tuy nhien, do d moi cong doan doi khi tuy thuoc vao loai nguyen lieu, miJc do saeh. ban eiia nguyen lieu, ma lUdng nUdc dinb mdc c6 the thay doi, va khi do rat kho xac dinh lUdng nUdc sii dung do viec thay nUdc phu thuoe vao mau nUdc va mUe do cam quan cua ngUdi eong nhan.

- Xi ngbiep ebUa c6 dong ho do nUde eho ttfng eong doan san xuat do do chUa xac dinh dUdc chinh xac lUdng nUdc sii dung cho tiing eong doan la bao nhieu, cong doan nao vUdt hdn so vdi dinb mdc.

71

- Mot so van nUdc. moi noi bi hu hong lam nude bi ro. that thoat ra ngoai.

- Y thUc tiet kiem nUdc eiia cong nhan cbUa cao.

- Ngoai ra viee dung 6'ng nhUa mem de ve sinh thiet bi nha xudng, ve sinh cac dung cu san xuat nhU thiing difng nguyen lieu, ro ra, thau chau cung la nguyen nhan lam tang lUdng nUdc sU dung.

Nude: 3.04m-

Da: 0.5 tan

2,lm;i+0,123m;!

Nudc

0,9mH0.817m'^

Tom nguyen lieu: 1000kg

Tie]D nhan nguyen lieu Rua Ian 1 Bao quan

Nirdc: 33,6m'^ Da: 1 tan

NUdc: l,5m^ Da: 0,25 tan

Da: 0,25 tan

Nudc: — •

Nudc thai 3,04 ± Aw(m-J)

Da: 0,5 tan ^ V Nudc thai: 3,36± A ^ (m-)

S' i ehe nguyen lieu |Nudc da tan: 1.5+ A\v

Nude thai: 1,5± A^y (m*') Riia lim 2, nhat tap chat [Nudc "dd ta"nro"25±2?u,

Phan cd hang

Rua Ian 3, de rao, can, xep khuon

Nude thai 2,1 ± Awta'O

Chd dong, cap dong. tach khuon, ma bang,

dong PE

Nude thai 1,777 ± Aw(m'^)

Bao goi carton

Bao quan

Hinh 2: Sd do can b^ng nUdc trong qua trinh san xuat torn

72

Can bang chat thai ran trong qud trinh che bien tom

* Qua ke t qua theo doi cua bo phan ky t h u a t ciia xi nghiej) cho thay:

- 1000 kg nguyen lieu (XL) dau vao sau khi ciua sd che khoi ludng

BTP thu dUdc t r u n g binh la 500 kg. Khdi ludng phe thai thu dude la

470 kg.

N h u vay lUdng phe tha i ran di vao dong thai t rong eong doan na>- la:

Phe tha i ran di vao dung thai - NL - BTP - Phe thai ran thu gom.

= 1000 kg- 500kg - 470 kg = 30 kg

500 kg BTP sau khi (lua cae cong doan riia Ian 2, nha t t ap chat ,

p h a n cd bang , riia kin 3 de tao den t h a n h p h a m (TP) cudi cung t r u n g

binh cd kbo'i lUdng la 490 kg LUdng phe tha i r an di vao dong thai long

t rong eac eong doan nay la: Phe thai r an di vao dong tha i long = BTP

- T P = 500 - 490 - 1 0 k g .

Tii ket (jua tren ta eo sd do can bang chat thai ran nhU sau (hinh 3):

Tom nguyen lieu 1000kg

Xiily

Phe thai ran Ihu gom: 470kg

Phe thai r n di vao dong thai: 30kg

BTF: 500kg

1 RUa. nhat tap chat phan cd hang

I Phe thai r^n di vao dong thai: 10kg

Thanh pham 490kg

Hinh 3: Sd do can b a n g c h a t t h a i r a n

Tu! sd do can b a n g chat tha i ran ta thay tong lUdng phe tha i di vao

dong tha i t rong qua t r inh san xua t torn la: 30 + 10 = 40 (kg/TNL)

73

LUdng phe thai nay di vao trong nUdc thai va day cung chinh la nguyen nhan lam cho nude thai che bien thuy san noi chung bi o nhi6m cac chat hUu cd nang. Oo do e^n phai c6 bien p h a p n h a m h a n ehe tdi da lUdng phe thai nay. Co nhU vay mdi lam giam dvrdc nong do cac chat 6 nhiom trong nude thai .

3 .4 . T i n h c h i p h i d o v i e c suf d u n g ni^dc

viftft d i n h mufc g a y r a

Chi phi dude t inh chii yeu t ren cd sd dien sii dung eiia may bdm

nUdc tUdng Ung v6i tong lUdng nUdc sii dung vUdt dinh miie ciia xi

nghiep hang nam: 7828.7nr', tUdng dUdng vdi 71 (ngay) sii d u n g

Xi ngbiep eo 3 may bdm nUde v6i tong nang lUdng tieu t h u la:

(1) May hut nudc tiT gicng Ion: 7.5kW/h x 12h/ngay x 71 ngay /nam =

6390 kW/nam

(2) May bdm Idn; 3.7 kW/h x 4h/ngay x 71ngay/nam = 1051 kW/nam

(3) May bdm nhd: 1.5 kW/h x 8h/ngay x 71 ngay /nam = 852 kW/nam.

T o n g = 8 2 9 3 (kW/nam)

Chi phi cho sii dung nUdc vUdt dinh mde t inh theo gia dien t r u n g

binh la 1000 dong/kW. NhU vay chi phi nang lUdng cho viec bdm nUde

diing VUdt dinh mdc la: 8293 x 1000 ^ 8.293.000 (dong).

Viec diing nUdc vttdt qua so vdi dinh miic se lam t a n g ehi ph i san

xuat eiia xi nghiep len 8.293.000 dong. O day ehung toi mdi chi t inb

den chi phi cho viee bdm nUdc. Trong thUe te, viee sii dung vUdt d inh

mUc se lam tang them eac ehi phi khac eho xi nghiep nbU ebi phi eho

hao mon may bdm. bao dUdng may bdm, chi phi xii ly nUdc thai , chi

phi cho eae van do moi trUdng pha t s inh do nUde tha i kbong dap l ing

dUoe cac yeu cau ve nUdc thai ebo phep theo TCVN 5945 - 1995.

3 .5 . D e x u a t c a c p h i i c f n g a n g i a m t h i e u v a x i l y n U d c t h a i

Qua ket qua phan tich nUdc thai trUdc va sau xii ly ciia xi nghiep

thay rang, he tbo'ng xii ly nUde tha i h ien tai ehUa hieu qua va khong

74

dap ijfng dudc cac tieu chuin chat lUdng nUdc thai hien hanh ciia Viet Nam (TCVN 5945- 1995 Loai B, va TCVN 6984 - 2001 (Q< 50m3/s, Fi). Nudc thai sau xii ly cua xi nghiep van con vUdt tieu chuan cho phep do'i vdi cac cbi tieu BOD, COD, pho't pho tong so', dau md dong thUc vat va coliform. Do do can c6 bien phap cai tao lai be thong xii ly nUdc thai de nUdc thai dau ra dap itng dUde eac tieu chuan hien hanh (xem bang 4).

TT

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

17

Bang 4. Ket qua phan

Thong so

Nhie t do

pH

COD BOD SS Ve Pb As Cd Dau md k h o a n g

Dau md dong thUc va t

Mn Tong nitd

Tong phot pho

Hg

S2-Coliform

Dtfn vi

oc _ mg/1

mg/1

mg/1

mg/1

mg/1

mg/1

mg/1

mg/1

mg/1

mg/1

mg/1

mg/1

mg/1

mg/1

MPN/ 100ml

tich ni/dc thai tai x

TCVN 5945-1945 (Loai B)

40

5 , 5 - 9

100

50

100

5

0,5

0,1

0,02

1

10

1

60

6

0,005

0,5

10.000

TCVN 6984-2001 (Q<50m3/

s , F i )

— 6 - 8 , 5

60

30

80

3

0,5

0,05

0,01

5

10

-_

5

-

-5000

n g h i e p F.37

Ni^dc t h a i

trifdc xuf ly

25,2

7,92

1970

1025

112

0,85

0,01

0,01

0,001

0,82

32,4

0.15

60,2

9,21

0,002

12.000

Nifdc thai sau

xijf l y

24,8

7,8

1449

811

36

0,25

0,01

< 0 , 0 1

0,001

0,65

24,5

0,11

51,59

9,56

< 0,002

0,33

14000

Nguon; [Bao cao danh gia tac dong moi trUdng Xi nghiep F. 37, 20031

Qua cac ket qua tren thay r^ng van de moi trUdng dang quan tam hang dau trong xi nghiep la van de moi trUdng nUdc. Vdi viec sii dung

75

nUdc vUdt dinh miic khong chi gay thiet hai ve kinh te cho xi nghiep ma con lam tang khoi lUdng nUdc thai ra moi trUdng. De ban che cac thiet hai ve kinh te va giam tac dong mdi trUdng, dudi day la cae bien phap dUdc de xuat.

Cac phi/cfng an tiet kiem nUdc

- Ldp dat dong ho do lUu lUdng nUdc d tifng khu vUc che bien ban che lUdng nUdc sii dung vUdt dinh mdc, dong tbdi de phat hien nhiing khau gay ton that nUdc cho xi nghiep.

- Nang cao y thdc tiet kiem nUde va tay nghe cua cong nhan.

- Dua ra cac bang dinh mijfc nUdc s^ dung cho tCfng cong doan che bien va cac so' gia thich hdp vdi moi loai nguyen lieu de tiet kien nUdc va dam bao chat lUdng san pham.

- Han ehe lUdng nUdc sii dung trong cong doan sd che nguyen lieu: (1) Thay dung nUde bang vdi sang diing nUdc bang chau hoac c6 the lap he tbo'ng vdi c6 te bao quang tU ngat khi khong sii dung; (2) Trong qua trinh sd ehe nguyen lieu c^n tach ngay phe thai ra khdi chau nUdc riia. Khong bo phe thai vao chau nUdc ma chi diing chau riia de nhiing phan nguyen lieu da dUdc xU ly; (3) Nudc diing trong cong doan ruta l§n 3 c6 the quay vong tai sii dung cho cong doan riia Ian 1. LUdng nUdc nay khoang 2,lm'^/TNL nhU vay tong lUdng nUdc tiet kiem dUdc trong cong doan nay trong mot nam khoang 636 m^/nam tUdng dUdng vdi sd tien tiet kiem la 344.000 dong. Nen lam ve sinh kho (nhu dung khan Udt hay dung cu ve sinh co xat) trUdc kbi dung nUdc de xa Ian euo'i.

- Thay viec diing 6'ng nhUa mem de ve sinh b^ng dung may bdm ap luc de tang hieu qua lam sach. Lap dat cac van khoa nudc tai dau cac 6'ng nhua mem diing de ve sinh thiet bi, nha xudng.

- Nudc t\i cong doan tach khuon va ma bang gan nhu la nUdc sach boan toan do do c^n xay dUng be thu hoi nudc trong cong doan nay de sii dung cho eac muc dich khac yeu cdu chat lUdng nudc kem hdn nhU dung de riia l4n 1, lam nUdc nhung ung hay thu hoi nudc nay de lam ve sinh c6ng nghiep. Ludng nudc dung de tai su dung nay khoang 1,717 m^/TNL. NhU vay lUdng nUdc tiet kiem dudc trong mot nam se la: 1,717 m^ x 302,7 =520 m^/nam.

76

Tuy nhien, viec quay vdng tai sii dung nUdc riia ciing can xem xet them qui dinh eiia Nganh nb4m tranh nbiim b^n trong thanh pham. Nude riia Ian 3 c6 the tai sii dung de ve sinh nha xUdng se phu hdp hdn.

Phi/cfng an xiC ly nUdc thai

Qua khao sat dac tinh nUdc thai ciia xi ngbiep, he thd'ng xii ly hien CO, dong tbdi de han che den miic toi da kinh phi cho xii ly nUdc thai cbiing tdi de xuat ra bien phap cai tao lai he tbo'ng xii ly nUde thai nhU sau;

Nudc thai sau khi qua be xii li ye'm khi eiia xi nghiep c6 cae tb6ng so dau ra nbu nhiet do la 24, 8^C, pH= 7,8, ty le BOD: N: P khoang 100: 5: 1. Day la dieu kien rat thich hdp cho qua trinh xii li hieu khi thdng qua be Aeroten [TranVan Nhan, 1999] hieu suat xii li eiia be Udc tinb khoang 85- 95%. Nhu vay, nUdc thai d^u ra se e6 ham lUdng cac chat hflu cd phii hdp vdi tieu chuan TCVN 5945- 1995 loai B. Nudc thai tiep tuc dUdc dUa qua be lang 2 de loai bd cac chat ran Id liing tao thanh sau qua trinb xii ly hieu khi. Tai day mot lUdng bun nhd se dUdc tuan hoan lai be Aeroten de tang toe do xii li ciia be. Sau khi qua be lang 2 nUdc thai dUdc khu trung de dam bao ham lUdng coliform eho phep CO trong nUdc thai. Co the bieu diln be thong xii ly cai tien nay bang sd do sau (binh 4):

Nudc thai tiep nhan nguyen lieu

Nudc thai che bien

Nguon tiep nhan

Be xii ly yem khi 3 ngan

Be kh^ triing Be lang2 Be Aeroten

Biin tuan hoan Cap khi

Hinh 4. Stf do he thong xu" ly nUdc thai de xuat cho Xi nghiep F.37

77

Cac thong so' ciia he thong xii ly nvtdc thai nang cap

* Tinh toan the tich cac be can xay dUng:

a. Be Aeroten The tich be Aeroten tinh b^ng cong thufc [Trinh Xuan Lai, 2000]:

V = Q x t trong do, V la the tich be (m^)

Q la luu lUdng nUdc thai ( m^I h)

t la tbdi gian luu bay tbdi gian can de oxi hoa chat hiiu cd tii nong do ban dau den nong do cuo'i. t dUdc tinb bang cong thiic sau.

t = o ~c p-X-d-z)

trong do: SQ la nong do BOD d^u vao

Sc la nong do BOD d^u ra

p la toe do oxi hoa rieng thUdng tii 12-30 g02/kg

biin boat tinh

X heu lUdng biin boat tinh trong be Aeroten tii 2-

5 kg/m^

z la do tro ciia biin, thUdng la 0,3.

Tii cac so' lieu dUa ra d bang 2 ta c6 tong lUdng nUdc diing cho san xuat ciia Xi nghiep (gom nUdc diing trong cac cong doan san xuat, nUdc san xuat da, nUdc ve sinh cong nghiep) la 28.080m3/nam. Trung binh so ngay san xuat trong nam la 200 ngay. NhU vay, khoi lUdng nudc sii dung trong mot ngay boat dong san xu^'t la: 28080m3: 200 ngay = 140,5 m3/ngay (5,85m3/h).

Nong do BOD ra khdi be xii li ye'm kbi la: SQ = 811mg/l

Nudc thai d^u ra theo de xuat la: Sc = 20mg/l (nUdc thai dat tieu chuan loai A TCVN 5945- 1995)

Cac gia tri p, X ebon gia tri trung binh la:

p = 21g02/kg biin boat tinh .

78

X = 3,5 kg/m3

Tbdi gian luu cua nUdc thai trong be la: t = 15,37 h

The tich be Aeroten can xay dUng la:

V = Q X t = 5.85 X 15,37 « 90 m3

b. The'tich be lang 2 va the tich bekhiC triing [Trinh Xudn Lai, 2000]:

Cong thiic tinh the tich be lang 2 va be khii triing la tUdng tU nhau do do se tinh toan the tich cho be lang 2.

Dien tich mat b^ng cua be lang 2 dUdc tinh theo cong thiic:

Q{l + a)-C„

s= c,.v, Q la lUu lUdng nUdc thai can xii li (m^/b)

^ la he so ' tuan hoan (thUdng c6 gia t r i 0,25 -H 1)

Co nong do biin boat tinh trong be Aeroten (thUdng cd

gia tri 2800 - 4000 mg/1)

Ct nong do biin trong dong tuan hoan (mg/1) (thUdng c6

gia tri 10000 mg/m^)

V] Van toe l^ng cua mat phan cbia phu thuoc vao nong do can l^ng. Doi vdi nong do biin can trong dong tuan boan la 10000 mglm^ gia tri V] c6 do Idn la 0,34m/b

Nhu vay vdi Q = 5,85 m^/h, cac gia tri a, Co, lay trung binh la: a - 0,6; Co = 3400mg/l ta tinh dUdc dien tich mat b^ng ciia be l^ng la: S = 9,36 m2

Chieu cao cua be l^ng ddt 2 (h) thUdng tii 3,7 - 6,1m, do do neu lay b = 4 m ta c6 th^ t ich be idng can xay dUng la: V = S X h =9,36 X 4 = 37,5 m^

The tich be khii triing c^n xay dUng la: 37,5m3

*Chi phi cho xay dUng he thong nUdc thai de xuat [Tran Diic

Ha, 1998].

79

Chi phi ebo xay dUng l m 3 be Aeroten Udc t inh la 900.000d6ng.

Chi phi cho xay dUng be l^ng 2 va be khii t r i ing Udc t inh la

600.000d6ng/m3.

Nhu vay ehi phi diing de xay dUng eho toan he tho'ng la:

900000 X 90 +600000 x (37,5 + 37,5) = 126000000 dong =126 tneu dong

Qua t inh toan sd bo tong chi phi eho xay dUng, cai tao lai he thong

xU li nude tha i cua xi nghiep Udc tinh la 126 t r ieu dong. Day la khoan

dau tu ckn thiet vi no khong nhOng giiip eho xi nghiep dap Ung dUdc

cae tieu chuan moi trUdng ma con giup giam eac tac dong tdi nguon tai

nguyen nUdc mat . Ngoai ra muc dich xii li nUde tha i khong chi dCfng

d viec de nUdc thai dau ra dat tieu chu4n xa thai . LUdng nUdc nay con

CO the tuan hoan tai sU dung de diing eho cac cong doan c6 yeu c&u

ehat lUdng nUdc khong cao nhu qua t r inh ve sinh cong nghiep. Dieu

nay c6 the giiip t iet kiem khoang 1348m-Vnam tUdng dUdng vdi so ' t ien

la 729.000d6ng/nam

Ngoai ra nUdc tha i t iep n h a n nguyen lieu va nUde tha i t rong eac

cong doan ehe bien nen tach r ieng va xii li sd bo trUdc kbi dUa vao he

tbo'ng xU li chung n h a m tang hieu qua cua qua t r inb xii li.

KET LUAN

Qua qua t r inh nghien crfu thUc hien kiem toan cha t t ha i vdi do'i tUdng chinh la day chuyen ehe bien tom cua Xi nghiep F. 37 c6 the dUa ra mot so ket luan sau:

1) Xi nghiep da quan t am den eong tac bao ve moi trUdng. Moi trUdng lam viee va moi trUdng xung quanh luon dUdc giU gin ve sinh sach se dam bao cae dieu kien san xuat an toan cho eong nhan .

2) Khi tha i va cha t tha i r i n ciia xi ngbiep chUa pha i la v a n de moi trUdng can quan t a m dae biet. Tuy nhien, Xi nghiep nen c6 bien phap de t an dung nguon chat tha i r^n nb^m giam lUdng cha t tha i r^n di vao nUdc tha i lam tang h a m lUdng cac cha t 6 n b i i m . 3) Nude tha i cua xi nghiep khi tha i r a moi trUdng chUa dap ling dUde cac t ieu chuan moi trUdng TCVN 5945 - 1995 loai B va TCVN 6984 - 2001( Q<50 m3/s, F l ) . Cac thong so 6 n h i l m con cao

80

hdn tieu chuan cho phep: BOD vUdt tieu chuanl6 Ian, COD vUdt 14 Ian, dau md dong tbUc vat vUdt 2,5 Ian, pho'tpho tong so'vUdt 1,6 Ian, va coliform vUdt 1,4 Ian. 4) Xi ngbiep da ap dung dinb mdc sii dung tuy nhien viec tbUc hien con chUa dUdc triet de va thieu dong bo trong tat ca cac cong doan. Do do, lUdng nUdc sii dung tang gap hdn hai l^n so vdi lUdng nude dinb miic. Tinb trang that thoat nUdc la do nhieu nguyen nhan nhU: ebUa s^ dung hdp ly n\Xdc trong cong doan sd ehe nguyen lieu ciing nhU qua trinb ve sinh cong nghiep, chua lap dat dong bo do nUdc va chUa thUc bien cac bien phap tai sii dung nUdc. 6) Cac giai phap tiet kiem nUdc dUa ra la rat kha thi, de dang ap dung dong tbdi se mang lai hieu qua to't ve kinh te va moi trUdng. Theo tinh toan sd bo chi rieng khau tach khuon, ma bang va khau rUa Ian 3 da c6 the tiet kiem dUde 1156 m^/nam, tUdng dUdng vdi 614.000d6ng/nam 7) Da de xuat mo hinh nang cap He tho'ng xii ly nUde thai cho Xi ngbiep F.37 nham dam bao van de moi trUdng nUdc cho xi nghiep va khu xung quanh vdi tinh toan sd bo kinh phi dau tU khoang 126 tneu dong va hieu qua kinh te la khoang 729.000d6ng/na.m.

TAI LIEU THAM KHAO 1) Bao cao DTM. Xi nghiep Che bien Thuy dac san xuat khau Ha Noi, 3- 2003. 2) Dang Xuan Toan, Tran ling Long. Hudng dan kiem toan giam thieu chat thai cong nghiep, Ha Noi, 1999. 3) Hoang Thi Trung Hieu. Nghien ct2u xii li chat ran Id liing trong niidc thai che bien Thuy san bang phitdng phap keo tu. Khoa luan tot nghiep khoa moi trUdng, 2002. 4) Tr^n Diic Ha. Xit li niidc thai sinh hoat quy mo vita va nho. TrUdng DH Kien True. NXB Khoa hoc Ki thuat, 1998. 5) Trinb Thi Thanh, Nguyen Thi Ha. Qiao trinh kiem toan chat thai cong nghiep. NXB DHQG Ha Noi, 2003. 6) Trinh Xuan Lai. Tinh toan thiet ke cac cong trinh xii li niidc thai. NXB Xay dung, Ha Noi, 2000. 7) Trinh Van Nhan, Ngo Thi Nga. Gido trinh cong nghe xit li nude thai. NXB Khoa hoc Ki thuat. Ha Noi, 1999.

81