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Tgp ehi Khoa hgc Tru&ng Dgi hgc Cdn Tha Phdn A Khoa hge Tu nhiin Cdng nghi vd Moi trudng 25 (2013) 76 84 Tap chl Khoa hpc Dai hpc Can Thd website sj ctu edu vn ITNG DVNG MO HINH TOAN MO PHONG DAC TINH[.]
Tgp ehi Khoa hgc Tru&ng Dgi hgc Cdn Tha Phdn A: Khoa hge Tu nhiin Cdng nghi vd Moi trudng: 25 (2013 Tap chl Khoa hpc - Dai hpc Can Thd website: sj.ctu.edu.vn ITNG DVNG MO HINH TOAN MO PHONG DAC TINH THUY LI/C VA DIEN BIEN CHAT LrONG NlTdC TREN TUYEN KENH XANG, THANH PHO SOC TRANG Truong Thi Ydn Nhi', Vdn Pham Dang Tri', Nguydn Thuy Kidu Didm" va Nguyen Hidu Trung' ' Khoa Mdi trudng vd Tdi nguyen Thien nhien, Trudng Dgi hgc Cdn Tha Sd Tai nguyen vd Mdi trudng tinh Sdc Trdng Thdng tin chung: Ngdy nhgn: 26/10/2012 Ngdy chdp nhgn: 25/03/2013 Title: Application of a hydrodynamic model to simulate hydraulic properties and water quality in the Xang Channel, the Soc Trang City Tir khda: Mo hinh thuy lire mgt chieu, chat luong nude, vd HECRAS Keywords: One-dimensional hydraulics model, water quality, and HEC-RAS ABSTRACT Application of a one-dimensional hydrodynamic model (HEC-RAS) lo simulate hydraulic properties (flow and water level) and water quality in the Xang Channel, the Soc Trang City After calibrating (Manning's n = 0,033), simulated water levels met the measured ones well (correlation coefficient was greater than 0.96) For calibrating the water quality module (dispersion coefficient D = 400 m2s-l, lime step = / hour, and initial condition of contaminant loads; COD = 13 mg/l BOD = 10,5 m^l, TN - 3,8 mg/l and TP = mg/l), the calculated error between observed and simulated data was lower than 20% Besides, the simulated water quality with scenarios oj changing the concentrations of contaminant (le COD, BOD, TN, and TP) in the Xang Channel was influenced by the changes of polluted masses and flows fi'om upstream Finally, the simulated water quality was also compared with the Vietnamese surface water standards (QCVN 08:2008, column A2, Bl) as a base of further discussion TOM TAT Md hinh thuy luc moi chieu (HEC-RAS) duoc sif dung de md phong dgc tinh thiiy luc (luu lugng vd muc mrdc) vd chdt lugng nude tren luyen kenh Xdng d thdnh phd Sdc Trdng Sau md hinh dugc hieu chinh vdi he so Manning's n = 0.03, muc nude duac md phdng gdn bdng muc nude thuc (he so tuang quan 1^ > 0,96) De hiiu chinh md hinh chdt luang nude (lie sd khuyen ldn D = 400 m s' vd diiu kiin ban ddu ciia cdc thong sd chdi lugng nude duac gdn cho COD, BOD, long dgm vd long ldn luang ung Id 13 mg/l, 10.5 mg/l, 3,8 mg/l vd mg/l), sai so giira cdc gid tri thuc vd md phdng thdp hon 20% Ben cgnh do, chdt lugng nude trin hi thong kenh Xdng cUng dugc md phdng dua tren cdc kich hdn thay ddi ve ndng dd chdt thdi vd lugng nude tir thuong nguon thay ddi Cudi cimg, chat luang nude mo phdng duac so sdnh vdi tieu chudn chdt lugng nude mat a Viet Nam (QCVN 08:2008, cdt A2, Bl) - day Id CO sd de ddnh gid chdt lugng nude mat md phdng de tdi Gidl THIEU Thanh phd Sdc Trang dang ttong thdi ky phdt tridn cdng nghidp va dd thi hda Bdn canh nhirng thdnh luu phat tridn kinh td-xa hpi mang lai, van dd d nhiem mdi irudng (ddc biel la mdi trudng nude mat) cung didn bien theo chidu hudng ngdy cang phiic tap; chdt lugng nude tai hau het cdc kenh rach tren dia ban loan Tap ehi Khoa hgc Trudng Dgi hgc Cdn Tha Phdn A: Khoa hgc Tu nhien Cdng nghe vd Mot Irudng: 25 (2013): 76-9$ Thanh hien dang ed ddu hidu d nhiem huu CO vd chdt rdn lo Itmg Tai cae khu vuc ndng thdn, ngudn nude mat bi d nhiem chu yeu nude thai tir boat ddng sdn xudt ndng nghiep va nudi trdng thuy san; dd, ddi vdi cac khu dd thi va khu cdng nghiep, chat thai rdn la ngudn chu yeu gdy dnh hudng ddn chdt lugng nude tai cac nhdnh kdnh / rach ndi thi [7] Trudc hidn trang dd, vdn de dat la phai cd gidi phap qudn ly thi'ch hgp, nhanh chdng vd hidu qud nhdm kidm sodt va gidi quyet hgp ly van dd vd sinh mdi trudng nude Trong nhung nam gdn day, vdi su phat tridn ciia cdng nghe thdng lin cung nhu khoa hgc ky thudt, cae md hinh toan iing dung linh vuc md phdng dac tinh thuy iuc vd chat Iugng nude cdng phd bidn va phat tridn nhu: HECRAS, MIKE, VRSAP, ISIS [10, 11] Vdi mdt so uu didm ndi bat (vi du, eho kdt qua tinh todn nhanh va linh hoat vide thay ddi cdc kich ban) md hinh loan irng dung dang ttd thdnh mdt nhiing cdng cu phuc vu ddc luc cho cdng tac qudn Iy tdi nguydn va mdi trudng [9] Do vay, nghien cuu dugc thuc hidn nhdm: (i) danh gid kha nang img dung eiia phdn mdm thdy luc chidu (HEC-RAS) eho h^ thdng song chiu tdc ddng bdi thiiy tridu d ddng bdng sdng Ciiu Long; vd, (ii) xem xet ddng thdi chdt lugng nude theo thdi gian ttong didu kien hidn tai va du bdo Ianttuydnd nhidm theo cac kich ban vd phdt tridn Thanh ph6 cung nhu su thay ddi ciia ddng chdy lir thugng nguon PHU'ONG PHAP NGHIEN CUtJ 2.1 Md hinh thiiy Iuc HEC-RAS HEC-RAS (phidn bdn 4.1) (phdn mdm thiiy luc chieu) &\iac xdy dung va phat tridn nhdm md phdng thuy Iuc ddng chay, chdt lugng nude va su thay ddi dia mao day sdng eua tiing nhanh sdng don Id hay ciia cd he thdng sdng phuc lap [4] He phuang trinh eo bdn sir dung HEC-RAS la phuong trinh lidn tue (1) va phuang ttinh dgng lugng (2): Phuang ttinh lidn tue md ta dinh ludt bao loan khdi lugng cho he mdt chidu: dA dt dS dt dx ^' (1) Phuong trinh dgng Iugng xudt phdt tir djnh luat bien thidn dgng Iugng: , 8(VQ) Bt dx ^fM- (2) Trong dd: x: Khodng each dge theo kenh (m); I: Thdi gian (s); Q: Luu Iugng (m^s'); A: Didn tich mat cdt udt (m^); S: Lugng iriS cua mat cdt udt (m^); q,: Luu lugng chdy vao lii- bdn, ttdn mot don vj chidu dai (m^s''); g: Gia tdcttgngttudng(ms"^); Sr: Dp ddc day sdng (khdng thii nguydn); vd, v: Van tdc trung binh ddng chdy (ms"') Hinh 1: Lug^c dd sai phanradhinh HEC-RAS Dao ham theo thdi gian: a / ^ A / _ 0,5(4/^,1+A/;) dt '~ At At Dao ham theo khdng gian: / , A/ _ (/,., - / , ) + ^( A/,„ - A/,) dx Ax Ax Gia trj ham: / » / = 0,5(/^ + /.,,) + 0,5e(A/, + A/^„) Cong thicc linh he s6 nhdm thuy luc He sd nhdm thiiy luc theo cdng thiic eiia Manning (3) [2] dugc sii dung vao vide hi|u Tap chi Khoa hoc Tnrcmg Dai hoc Cdn Thcr Phdn A: Khoa hoc Tit nhien Cong nghe va Moi truong: 25 (2013) • 76-84 chinh Icet qua mo phong dac tinh thuy lyc cua dong chay (?=ifi;VZyl (3) i Q =~R3^riA Trong dd, Q: Luu (ManninV); n: Hd sd nham tha>; Iuc (sm'"^); R: Ban kfnh ththuy Iuc (sm]nh kdt qud md phdng khdng thn kinh t); va, A: Dinh ththuy Iuc (sm]nh k') 2.2 M o hinh chat lugng nirdc Nhung thdng sd chdt lugng nude bao gdm nhirng hdng sd ty le eua nhiing phdn iing Iy hge vd hda hgc giiia lao, Nito, Photpho, DO, COD, BOD vd trdm tfch Nhirng hdng sd ty Id kidm sodt ty Id gidi ban cung edp/tieu thu ttong phuong trinh truydn tai - khuech ldn (4): -W) = ^ {Q,f>)Ax + ~(VA^)Ax±S ftc dx (4) Trong dd, V: Thd tfch cua d ludi chdt lugng nude (m^); ^ : Nhidt nude ("C) hoac ndng dd chdt nhiem (kg m"^); Q: Luu iugng (m^ s"'); r : He sd phdn tan dugc xdc dinh bdi ngudi sii dung (m^ s ' ) ; A: Dien Ifch mat cdt udt (m^); va, S: Chi sd cung cap vd tieu thu (kg s"^) Phucmg trmh tinh todn he so phdn tdn mo Mnh HEC-RAS Phuang ttinh tinh todn he sd phan tdn ciia Fischer dugc ung dung ttong IffiC-RAS Theo do, he s6 phan tan dirge tinh theo cong thfc (5) [3].- D = 0.011y^ (5) Trong dd, u: Van toe trung binh ddng chay (ms"'); w: Do rdng trung binh kenh (m); y: Do sdu trung binh kdnh (m); va, u': Van tdc trung binh cdt doc sdng (ms'); u' duoc xac dinh bdi (6): u =yfgdS (6) Trong dd, g: Gia tdc ttgng trudng (9,81 ms"^); d: Dp sdu trung binh kenh (m); va, S: Do ddc mat nude (khdng thii nguydn) 2.3 Thanh l^p md hinh Cdc so lieu ddu vdo cdn thiet cho phdn thuy luc cda mo hinh - DH lieu hinh hoc: Sd lieu thuc ve mat cdt cua doan kenh dugc md phdng (dugc tham chidu dia ly eu thd) - Dieu kiin bien: Bien trdn la chudi gia tri luu Iugng tinh toan theo thdi gian (tir gid ddn 20 gid ngdy 27.9.2009) tai mat cdt sd (Hinh 2a); bien dudi la chuoi gia tri muc nude thuc theo thdi gian (tir gid ddn 20 gid 27.9.2009) tai mat cdt sd (Hinh 2a) Hinh 2: Vj tri dac s6 li^u ve thiiy ^ (a) va chat lugng nude (b) tren do^n kenh Xang Tap ehl Khoa hoe Tnr&ng Dai hge Cdn Tha Cdc sd lieu cdn thiit luang nuac cho phdn Phdn A Khoa hgc Tu nhiin Cong nghi vd Mdi Iru&ng 25 (2013): 76-9* chdt Diiu kien ban ddu: Ndng thuc ban ddu eua cac bidn chdt lugng nude tren kenh (COD, BOD, Nito tdng (TN) va Photpho tdng (TP)) tai cdc didm NMl, NM2, NM3, NM4 vaNM5(Hinh2b) - Tdi luong gia nhdp: Tdi lugng (tinh loan theo quy dinh cua Thdng ttr 02/2009/TTBTNMT [8]) eua thdng sd chdt lugng nude (COD, BOD, TN va TP) tai vi tti tuong img vdi cdc cdng thai cua Nhd may chd bien thuy san (Stapimex, Thdi Tdn, va Phuong Nam tuoiig ling vdi mat cat 1, 2, vd 5) (Hinh 2b) 2.4 Hieu chinh va kiem dinh md hinh sai [5] cho ddn kdt qua md hinh duge ddnh gid la phu hgp vdi kdt qud thuc Sau dd, mo hinh dugc kiem dinh bdng bg dii lieu Ihuy lgc va chdt Iugng nude (thue do) tii 21 gid 27.9.2009 ddn gid 28.9.2009 2.5 Xay dung cac kich ban d y bao chat lugng nude Vide xdy dung cac kich ban cho md hinh dua tren su thay ddi tdi lugng thdi vd luu Iugng nude d thugng ngudn (Bdng 1) Trong dd: - Kieh ban A - dugc xdy dung iing vdi: (i) Luu lugng thdi tang 50% va 70% gid djnh cd su md rdng quy md san xuat cua nha mdy chd bien thiiy san; va, (ii) Luu lugng nude thugng ngudn tang 10% va 20% vdo mua mua va gidm 10% va 20% vao miia khd Md hinh dugc hidu chinh dua vao (i) bd sd ~ Kieh bdn B - Kieh ban dugc xay dung lieu thuy luc; vd, (ii) bd sd lieu chat lugng nude ling vdi vide dp dung cdng nghe xu ly nude thai (ndng COD, BOD, TN vd TP) thuc tir dugc edi lidn, ndng ciia cac thdng sd d nhiem gid den 20 gid 27.9.2009 bdng each thay ttong nude thai sau xir ly dat QCVN ddi cac thdng sd md hinh (he sd nham 11:2008, cgt B (ddi vdi nude thai cdng nghiep): thuy Igc Manning's n ttong phdn md phdng (i) Luu lugng thai tang 50% vd 70% (gi6ng thuy luc va he so phdn tan (D) phdn md kieh ban A); va, (ii) Luu Iugng nude thugng phdng chdt lugng nude) Viec chgn thdng sd ngudn giam 10% vd 20% md hinh duge thuc hidn bdng phuang phap thii Bang 1: Kjch ban md phong ch^t Iugng nu^c tuong lai Kich ban Luu lugng nuiVc thugng nguon Luu lugng va nong dp thai tix cac nha mdy Lmi lugng thai tang 50% va 70%; Nong dp thai tir cac nha may khdng Ihay ddi so vdi kjch ban hi?n t^i Luu lugng thai tang 50% va 70%; Kich ban B -10%;-20% Ndng thai tir cac nha may sau xu ly giam theo dung QCVN 11:2008 Xang tuong lai ed su thay ddi luu Chdt lugng nude md phdng dugc so sanh lugng nude tir thugng ngudn va su gia tdng td! vdi QCVN 08:2008 d cot Bl vd A2 (Bdng 2) dd lugng thai danh gia miic d nhilm trdn doan kdnh Kich ban A ±10%; ±20% Bang 2: Chi tieu chat lugng nuo'c dugc Iga chpn dl so sdnh (QCVN 08:2008) Thong so chat lugng nude COD BOD Nitrat (NO3) tinh theo Nito Pffn v} mg/l mg/l mg/l K £ T QUA VA THAO LUAN 3.1 Ket qua tinh todn thuy luc Md hinh thuy luc dugc hidu ehinh thdng qua vide thay ddi he sd nhdm thiiy tuc Manning'^ n Trong dd, vdi he sd nhdm thuy luc n = 0,033, kdt qud mirc nude md phdng d mat cdt (mat QCVN loai A2 QCVN loai Bl 10 30 15 10 cat 2, va 4) phii hgp vdi thue (Hinh 3a, b va e) Ket qua kiem dinh md hinh vdi bp dD lieu tir 21 gid ngdy 27.9.2009 ddn gid 28.9.2009 dugc thd hidn ttong hinh 4a, b va c Cd thd thdy, muc nude md phdng khodng thdi gian kidm dinh khdng dugc chfnh xac nhu d phdn hidu chinh Su sai ldch giua muc nude Tgp chi Khoa hgc Tru&ng Dgi hgc Cdn Tha Phdn A: Khoa hgc Tu nhien Cdng nghe vd Mdi Iru&ng: 25 (2013): 76-84 thuc va md phdng d phdn kidm dinh la do ddc mdt nude d chuoi sd lieu hieu ehinh (tir gid ddn 20 gid 27.9.2009) va d chudi sd lieu kidm dinh (tir 21 gid 27.9.2009 ddn gid ngdy 28.9.2009) khac (Hmh 5) Theo phuong trinh he so nhdm thuy luc Manning's n thaj; ddi ddc day (hay ddc mat nude) thi he sd nham thuy Iuc eung se thay ddi; dd, d trudng hgp vi ed chudi gia tti dd ddc khde nen edn phdi ed gid tti he sd nhdm thuy luc tuong iing Mac du vay, sai khac giua ket qud tinh loan cua mue nude thuc va md phdng vdn ndm khoang tin eay vdi he so Nash - Sutcliffe (E) tren 93%, (Hinh 4a, b vac) i:::«!-! i5!«:' tboifUB (gw) Hinh 3: Mue nirfrc thye va md phong tai m^t cdt (a), (b) vd (e) \if\ hd sd nham thiiy Igc n=0,033 (9 %iif - 20 gior ngdy 27.9.2009) DJtO fh0igiH(gM') ihoi^ui (giir) Blgiff) TTIHII J \%or nnoir rtinr ito n •rntH wiAna h talf eit ? lm\ \ tWt rk lr\ i-ni ti> u nhMH thnv Inr •• — A Ott 1^1 »ir, BC Hinh 4: Mue nude thyc vd md phong d mat cdt (a), (b) va (e) vdi hf s6 nham thuy lye n = 0,033 (21 gifr 27.9.2009 d^n gid 28.9.2009) £ 0EJJ4 i Hinh 5: Dp doc mat nuo'c (md phong) tuong ung \in sy thay ddi myc nmS'c 24 gior 35 1,3E4» S , ^ OE-04 Q5.OE.0S _ ' •**• ••• 00E*00 ^-^ -••• 11 13 15 17 19 21 23 3.2 Kdt qua tinh toan chat lugng nude He sd phdn tan theo ehidu dgc ciia ddng chdy trdn sdng tu nhidn thay ddi tCr 10 - 1,000 m"s"' nhdm phdn dnh su khac bidt ciia he sd phan tan dgc, dac linh hinh thai vd thuy van dnh hudng ddn qud ttinh khuech tan vd truydn ddn Ml Vi vay qua ttinh hidu chinh chdt lugng nude duge thuc hidn nhieu ldn (lir he sd phdn tdn (D) bdng 10 ddn 1000 m"s"'); ttong dd, vdi he sd phdn tdn D = 400 m"s"', budc thdi gian la gid vd didu kidn ban ddu nhu sau: COD la 13 mg/l, BOD la 10,5 mg/I, TN la 3,8 mg/l va TP la mg/l thi cac kdt qud md phdng phu hgp vdi thuc (Hinh 6) Mac dii vdy, vdn ton tai nhiing sai sd nhdl dinh va didu cd thd ly giai do: Trong md hinh HEC-RAS, doan kdnh nghien cuu ddi 800 m bj gidi han bdi mat cdt va chia doan, ket qud md phdng chdt Tgp chi Khoa hoc Ti-udng Dai hge Cdn Tha Phdn A: Khoa hgc Tu nhien, Congnghi vd Mditrudng: 25 (2013): 76-84 lugng nude xuat tii md hinh la d didm tten doan kenh giira mdt cdt (gia tri didm md phdng chdt lugng nude thay ddi theo thdi gian) Nhu vay, kdt qua md hinh lai mgt diem dai dien eho mdt doan sdng giiia mat cdt la kha rgng cdn vide lay mau dac thi lai dugc thuc hien ttdn vi trf xdc djnh; ket qua tij md hinh chi the hien dugc didn bidn eiia ndng cdc chat md phdng tir d o ^ sdng sang doan sdng khac nhung khdng dien td duge ddng thai d nhiem cue bd d khu vuc nhd Bdn canh do, day Id md hinh chieu nen viec md phdng chi theo phuong dgc cua ddng chdy va khdng thi phan anh day du dac tinh ddng chdy nhu d cac md hinh hay chieu acoD_TlniciIft acC>D_MAplu9osj, ^ Hmh6:N6ngdOCOD(a),BOD(b),TN (c) vd TP (d) md phong vd thyc tai vj tri doc kdnh Xang IE H £11 ILi! H nun fin K^ _ NMl NNC NM3 ^•^^l ^^ts V,m ^ »n SMJ ^oo NNM sots I yyt^\ iEllllfiyiEDdilBl SMI Hinh md td ddng thai COD theo thdi gian ma khdng phan tfch su thay ddi cua cdc chi lidu BOD, TN vd TP Nguyen nhdn la ndng COD thai tu cdc nha may chd bien thuy sdn ndm trdn doan kdnh Xang vugt QCVN 11: 2008 nhidu ldn (Theo Sd Tai nguydn vd Mdi trudng tinh Sdc Trang (2009), thdng sd COD nude thdi chua xu ly cua nganh chd bidn thuy san Id 785 mgi'', gdp khodng 10 Idn so vdi QCVN 08:2008, cdt B), ddng thdi gid tri COD va BOD cd su tuong quan vdi nhau, ndn chi cdn xem xet vdi chi tidu COD Ben canh dd, viec phdn tfch chi nhdm xem xet dien bidn thay ddi ndng chat d nhiem theo thdi gian cung nhu thay ddi luu lugng nude thugng ngudn dnh Hinh 7: COD md phong tang (giam) luu lugng nude thugng nguon (Q); tru&ng hgp tai Iugng thai tSng 50% (a va b) va 70% (c va d) tai doan kdnh tir m^t cdt d^n »C NM) MJl MM5 hudng nhu the nao den kdt qud md phdng chat lugng nude Cd thd thdy gid Iri ndng dd COD tang tdi lugng thai cua cac nhd may tang Bdn canh dd, vdi eae trudng hgp gia tang luu Iugng nude sdng d thugng nguon thi nhin chung chudi gid tri ndng dg COD thap ban so vdi cac trudng hgp luu lugng nude thugng ngudn giam Ngoai ra, ndng COD bidn thidn theo van loe ddng chdy, vdn tdc dong chdy nhd thi nong dp d nhidm tdng cao va ngugc Iai Kdt qud md phdng ndy phii hgp vdi kdt qud phdn tich bien thidn ndng COD theo thdi gian d vj tti thu mdu nude mat gdn nhd may Phuong Nam Tgp chi Khoa hx Truing Dai hoc can Tho Phin 4: Khoa hoc Tunhiin Congnghi va Mot truong: 2S (201 i): 76-S4 3.3 Dien bi£n chat lutfng niro'c tren doan kenh Xang theo c i c kjch ban duoc xay dmig TP d doan tu mat cdt ddn mat cdt (Hinh 8, va 10) ' ^ Theo kich ban A va B da dugc xay dimg thi hiu hit dSu cho ket qua diln bifa COD va TN tren cac doan kenh dSu khong vugt QCVN 08:2008 cot B l Tuy vay, gia tri BOD mo phong lai vuot gia tri quy dinh o cot Bl a mot s6 thoi diem nhit dinh D6i vdi chi tieu TP thi khang so sanh voi QCVN 08:2008 dugc vi Quy chuan khong quy dinh doi voi chi tieu Ngoai ra, so sdnh kk qua ciia cac chi tieu COD, BOD va TN vdi cgt A2 cua QCVN 08:2008 thi 6hu cao hon rit nhi6u Sau day sg chi xem xet k6t qua COD, BOD, TN va Vdi cac kich ban gia tdng tai lugng thai vd luu lugng nude thugng ngudn thi hdu het cae chi tidii ddu vugt QCVN 08:2008 d miie A2 nhieu ldn, nhung vdn chua vugt nguong d cdt B1 Kdt qua phdn anh viec luu lugng nude ttdn kenh van cdn du ldn dd pha loang vd phan tan cae chdt d nhiem theo thdi gian Tuy nhidn, chi lieu BOD md phdng vugl miie B i d mdt vai trudng hgp ttong chudi thdi gian md phdng (Iuc 17 gid, 18 gid, va tir gid ddn gid) (Hinh 8b vd 9b), ddng thdi da sd cae trudng hgp vugl ehudn la thugc kich bdn gidm luu lugng nude thugng ngudn 10% vd 20% Kit qud kich bdn A ,= r= 1-4-00 M 15-50 li.i0 ^^j 19.00 ^I'^'Qf^ s n QtioiIC * — QC.-:; A2 13 iS r —• (a> i9 : i _ ; j i ; i ~ Q ^ ? N B : '* (hM giSB (siig (b) 730 s n 1.; 15 r 19 21 25 ! S - -—QC^^NA: 11.00 , St -S 9,00 7.00 n QC.7.- XI 13 l i 1' 19 21 23 • QC\-N Bl I LS 17 19 31 23 t Hinh 8: Kk qua diln bien COD (a), BOD (b), TN (e) va TP (d) gia tang tai lugng thai 50% or doan kenh tu m|t cat din mgt c5t so sdnh voi QCVN 08:2008 theo kich ban A i\ 13 i ; 1" 19 :\ 2= "SJ^-J-'?'" — Đ ^ ? a ? * ôfcM Bi-B (gi*) Hinh 9: Kit qua diln biln COD (a), BOD (b), TN (c) va TP (d) gia tang tai lugng thai 70% d dogn kenh tu mgt cdt den mgt cSt so sanh vol QCVN 08:2008 theo kjch ban A Tgp chi Khoa hgc Tru&ng Dai hge Cdn Tha Phdn A Khoa hgc Tu nhien, Cdng nghe vd Mdi iruang: 25 (2013): 76-84 Kit qua kjch ban B kich ban B, ndng cua ede thdng sd d nhidm nude thai sau xii ly dat QCVN 11:2008, cdt B (doi vdi nude thai cdng nghiep) ndn hdu hdt cac kdt qud ciia ede ehi tieu COD, , | JOO ' ^ ]linSiTlP2123 I S •• ,1 •••• Qpiml3% — — QCTI-NA: QpaaB20H i, BOD vd TN d cac trudng hgp tdi lugng gia tang 50% va 70% ddu cho kdt qud khdng vugt QCVN 08:2008 d cdt B l Do vdy, Hinh 10 ehi the hidn kdt qua ddi vdi ttudng hgp tai lugng thai cua nha may tang 70% 11IS13iri93l23 S -QCVN A; QpiBld'i QpimJM* - QC\2i A2 — * — Qa-NBl Hinh 10: Kit qua diln biln COD (a), BOD (b) va TN (c) gia tdng tai Iugng thai 70% fr doan kdnh tu mat c3t den mdt eat so sanh vol QCVN 08:2008 theo kich ban B KET LUAN K^t qud cho thay, md hinh thuy Iuc chieu (HEC-RAS) cho kdt qud md phdng thdy Iuc cd tin cay eao, ddng thdi md hinh cung cd thd dugc dp dung nhdm md phdng vd du bdo chdt lugng nude d doan kdnh Xang ttdn dja ban tinh Sde Trdng D6i vdi ph^n thuy lure: Sau hidu chinh, md hinh ddm bdo dg chinh xac cdn thidt vdi budc thdi gian tinh toan Id gid vd he sd nhdm thuy luc n = 0,033 D6i vdi phkn chdt lugng nude: Vdi hd so phan tdn D = 400 m V , budc thdi gian la gid va dieu kien ban dau dugc xdc dinh (COD = 13 mg/I, BOD = 10,5 mg/l, TN = 3,8 mg/I vd TP = mg/I) thi sai sd giiia ket qud tinh todn vdi ket qua thuc nhd hon 20% Goi vdi phan d u bao chat lirgng nirdc: Su thay doi ndng COD, BOD, TN va TP trdn doan kdnh chiu dnh hudng bdi su gia tdng ldi lugng thai ciia cac nha may va phu thudc khdng nhd vao su thay ddi luu lugng nude thugng ngudn Vdi kjch bdn A: Khi so sanh cae chi lieu md phdng (COD, BOD vd TN) d eae trudng hgp khdc vdi QCVN 08:2008, kdt qua md phdng ddu vugt muc Trong dd, ddi vdi miic Bl thi chi cd ndng BOD Id vugt quy dinh d mdt vai thdi didm (Hinh va 10) Ben canh dd, da sd cac thdi diem vugt c h u ^ la gidm luu lugng nude thugng ngudn 10% va 20% Vdi kjch bdn B, cae chi tidu COD, BOD va TN ddu khdng vugt QCVN 08:2008 d miic BI, nhung vdn vugt miic A2 Tuy nhidn, neu sir tiep nhdn ldi lugng thdi cua doan kdnh la lien tuc vd chiu anh hudng bdi nhidu ngu6n thdi khdc chua dugc dua vao md hinh (nude thai sinh boat tir khu dan cu, nude chdy tran tii be mat ddt, ), cdng vdi viec gidm luu lugng nude thugng ngudn ngdy cang ldn ttong tuong lai thi cd the cae chl lieu se vugt chuan nhieu ldn Didu se anh hudng ddn siic khde va sinh boat cua ngudi dan xung quanh ttong dieu kidn hidn tai da sd cdc hg ddn ddu su dung nude trdn kdnh vao muc dich sinh hoat Vl vdy, tuong Iai, cac nhd may ndn cd he thdng xii 1^ nude thdi tot ban dd dam bao ddu khdng vugt quy chuan quy dinh; ddng thdi, can xem xet lua chgn su gia tang quy md ciia nha mdy cho phii hgp vdi he thdng xii ly nude thai Tuy vdy, ket qud eua nghidn cihi chi dugc thuc hidn ttong mdt doan kdnh ngdn vdi chudi sd lieu ddu vdo ehi 24 gid, ndn chua the hidn het dugc d^c tinh thuy lue va didn bidn chdt lugng nude mdt each chi tiet thdi gian dai Mgc dti vdy, ket qud chi Id budc eo ban nhdm t?o tidn de can thidt dd thuc hidn nhung nghidn euu vd sau vdi mang ludi sdng ngdi cd dac tinh ddng chay va ngudn xd thdi Tap chi Khoa hgc Tru&ng Dgi hgc Cdn Tha Phdn 4: Khoa hge Tu nhien Cong nghe rd Mdi iru&ng 25 (2013): 76-84 phirc tilp hon Bdn canh dd, kdt qud md phdng doi vdi chi tidu TP vdo khoang thdi gian cudi md phdng lai tang cao (Hinh 9, 10) Tuy nhidn, ehi tidu ndy (TP) khdng duoc quy dinh ttong QCVN 08:2008 nen khdng thd so sdnh vd danh gia dugc; vdy, nghien ciiu vd ddng thai d nhiem ngudn nude mat chi tidu TP dugc 6.1 xudt dd nghien cuu sau hon lam co sd de dua vao QCVN, dac biet la d nhung vCing cd ddc thii phat ttidn nha may chd bien Ihuy san Ngoai ra, de ehinh xac eua md hinh tdt hon thi chuoi sd lieu quan trdc phdi dugc dac ttong thdi gian dai (thang hodc nam) ve cd dac tinh thuy Iuc vd ch^l Iugng nude TAI LIEU THAM KHAO Biii Ta Long, 2008 Mo hinh hoa mdi tnrdi^ Nha xudt ban Dai hpc Qudc gia Thanh phd H6 Chl Minh, 447tt Chow, V T, 1959 Open Channel Hydraulics McGraw-Hill Book Company, Inc, 6%Qpp FischerH.B ListE.J., KohR.C.Y ImbergerJ., & Brooks N.H., 1979 Mixing in inland and coastal waters Academic Press, New York, 483pp Gary W B., 2010 HEC-RAS River Analysis System Hydraulic Reference Manual Version 4.1, US Army Corps of Engineers, American, 790pp Phgm The Bdo, 2009 Cac phuong phap giai quydt bai loan tren may dnh Khoa Toan - Tin, Trudng D^i hgc Khoa hpc Tu nhien, lOtt Sd Tdi nguyin Mdi Irudng tinh Soc Trdng, 2009 Bao cao '"Danh gia tac dgng moi tnrdng Du an ddu lu Xi nghiep Chd bidn thiiy hai san Khanh Lgi" Sd Tdi nguyen vd Mdi irudng tinh Sdc Trdng, 2010 Bao cao "Hidn trang moi truong linh Sdc Trang giai doan 2006 - 2010" Thong ne 02/2009/TT-BTNMT Quy dinh ddnh gid khd ndng tiep nhdn nude ihdi cua nguon nude Trdn Hdng Thdi Vuong Xudn Hoa, Nguyen Vdn Thao vd Le VU Viet Phong, 2009 U'ng dung md hmh loan hpc tinh toan du bdo xu the dien bien chdt lugng nude phu thupc vao cdc kich ban kinh tl xa hpi luu virc song Sai Gdn D6n§ Nai Tuydn tap bao cao Hpi thao Khoa hpc ldn 10, Vien Khoa hgc Khi tugng Thuy van va Moi truimg, tt.304 - 313 10 Van P.D.T Carting P A and Atkinson P M., 2012 Modelling the bulk flow of a bedrockconstrained, multi-channel reach of the Mekong River, Siphandone, southern Laos Earth Surf Process Landforms 37 : 533 - 545 doi: 10.1002/esp.2270 11 Van, P.D.T., L Popescu, A van Grienven, D Solomatine, N.H Trung and A Green, 2012 A study of the climate change impacts on fluvial flood propagation in the Vietnamese Mekong Delta Hydrol Earth Syst Sci Discuss., 9, 7227 - 7270, doi: 10.5194/hessd-9-7227-2012