Cng ngh v cng trnh ph hp x l nc thi bnh vinPGS.TS Trn c HVin Nghin cu Cp thot nc v mi trngc im s lng v thnh phn tnh cht nc thi bnh vinHng ngy mt lng ln nc thi y t c x trc tip vo mng li thot nc th hoc cc vc nc mt xung quanh bnh vin (BV). Do c th khm v cha bnh, nc thi y t bao gm nc thi t phu thut, iu tr, khm, cha bnh, xt nghim, git gi, v sinh ca ngi bnh, nhn vin y t... b nhim nng v mt hu c v vi sinh vt... to nn nguy c nhim, ly lan dch bnh cho cng ng. Theo thnh phn v ngun gc hnh thnh, cc ch tiu nhim trong nc thi BV c chia thnh 3 nhm:Cc ch tiu nhim hu c v cc cht dinh dng: Nc thi BV v cc c s y t c mt s thnh phn ging nh nc thi sinh hot, cha lng ln cht rn l lng, cht hu c c trng bng ch tiu BOD5, cc cht dinh dng nit v phtpho. Trong nc thi hm lng BOD5 thng dao ng t 80 n 250 mg/1, ph thuc vo loi hnh, quy m v c im ca BV. Trong nc thi cc c s y t, hm lng nit amoni thng dao ng t 30 n 50 mg/I. Tuy nhin, i vi cc BV a khoa v cc phng khm, do qu ti trong vic s dng khu v sinh nn hm lng nit amoni trong nc en c th ln ti 80-120 mg/1, ln hn trong nc thi sinh hot v nc thi th nhiu ln.Cc ch tiu vi sinh vt Nc thi BV v cc c s y t cha vi khun gy bnh, c bit l nc thi t nhng BV chuyn khoa cc bnh truyn nhim v bnh lao, cng nh nhng khoa ly v cc phng xt nghim ca cc BV a khoa. Nhng bnh truyn nhim thng gp lin quan ti cht thi y t gm: bnh t, thng hn, ph thng hn, do khun Salmonella, l, bnh do amip v mt s bnh khc.Cc cht nhim c bit: T qu trnh in trng phim chp X - quang hnh thnh nn cc ha cht c hi dng lng c th b dn vo h thng thot nc BV v cc c s y t. Trong thnh phn cht nhim t nc thi ca qu trnh chp X - quang c cc cht AOX v cc hp cht bc. Cc cht thi phng x lng pht sinh t cc hot ng chn on, iu tr, nghin cu v sn xut... Cc cht khng sinh nh Amoxicillin, Ampicillin, Penicilin... c trong nc thi khoa dc hoc nc thi trong qu trnh iu tr, c cu trc Beta-lactam (?-lactam). Hin nay, nc thi c cc hp cht ny rt kh x l bng cc phng php thng thng.Vi cc thnh phn nhim trn, khi x ra mi trng bn ngoi, nc thi BV v cc c s y t lm thay i ch xy, gy hin tng ph dng cc ngun nc mt. Cc cht nhim trong nc thi khng c x l khng nhng nh hng trc tip n nc ao, h, sng m ngm xung t, tch ly tn ng trong ngun nc ngm. Ngun nc thi cha vi khun gy bnh c th dn n dch bnh cho ngi v ng vt qua ngun nc v cc loi rau c ti nc thi.Vic s dng rng ri cc cht ty ra (cht hot ng b mt) xng git l ca BV cng c nhng tc ng xu n cng trnh x l nc thi (XLNT). Cc cht hot ng b mt c kh nng to huyn ph trong b lng v a s vi khun t tp trong bt.Hin nay, ti nhiu BV v c s y t, nc thi khng c thu gom nn chy ra cng thot nc hay trn ra cc ao, h, knh mng xung quanh. Vn ny e da n cht lng mi trng, c bit l nh hng nghim trng n sc khe ca bnh nhn n khm cha bnh cng nh cng ng dn c trong khu vc.Nguyn tc la chn cng ngh v thit k cc cng trnh XLNTBVQuy ch Qun l cht thi y t, ban hnh km theo Quyet nh s 43/2007/Q-BYT ngy 3/12/2007 ca B trng B Y t quy nh v hot ng qun l cht thi y t, quyn v trch nhim ca cc c s y t v cc t chc, c nhn trong vic thc hin qun l, x l v tiu hy cht thi y t. Theo Quy ch ny, mi BV phi c h thng thu gom v XLNTngb.Cng ngh XLNT y t phi p ng cc tiu chun mi trng, ph hp vi cc iu kin a hnh, kinh ph u t, chi ph vn hnh v bo tr. H thng XLNT y t phi c quy trnh cng ngh ph hp, XLNT t tiu chun mi trng; Cng sut ph hp vi lng nc thi pht sinh ca BV; Ca x nc thi phi thun li cho vic kim tra, gim st; Bn thi t h thng XLNT phi c qun L nh cht thi rn y t.BV phi c h thng thu gom ring nc b mt v nc thi t cc khoa, phng. H thng cng thu gom nc thi phi l h thng ngm hoc c np y. H thng XLNT phi c b thu gom bn. BV phi nh k kim tra cht lng XLNT, c s qun l vn hnh v kt qu kim tra cht lng lin quan.Cng ngh ph hp XLNT BV c la chn trn c s cc yu t: Lu lng, ch thi nc v thnh phn, tnh cht nc thi BV; Cc yu cu v sinh khi x nc thi BV ra ngun tip nhn theo quy nh ca Quy chun mi trng QCVN28:2010 - Quy chun ky thut quc gia v nc thi BV; Din tch t c quy hoch xy dng trm XLNT BV v v tr ca n i vi cc khoa, phng trong BV cng nh khu dn c ph cn; iu kin vn hnh v bo dng cc cng trnh XLNT.V nguyn tc, nc thi y t cn phi c x l sinh hc (t nhin hoc nhn to) v kh trng trc khi x ra mi trng bn ngoi. S khi h thng XLNT BV hoc cc c s y t c nu ti Hnh 1.Theo s ny, trong giai on tin x l, cc loi nc thi v sinh (nc en) cc khoa (phng) iu tr qua cc b t hoi, nc thi y t c bit (khoa dc, X-quang...) c x l s b v nc thi tm git (nc xm) c tch bt v lng ct. Sau ton b lng nc thi ny c a v cc cng trnh x l sinh hc. y c th l cc cng trnh x l sinh hc nhn to theo nguyn tc hiu kh (O), thiu kh- hiu kh (AO) hoc ym kh -thiu kh - hiu kh (AAO); hoc cc cng trnh x l sinh hc trong iu kin t nhin theo m hnh Dewats (h sinh hc hoc bi lc ngm trng cy). Nc thi sau cc qu trnh ny c x l cc cht nhim hu c (BOD), cc cht dinh dng (nit, phi pho)... m bo cc quy nh ca QCVN 28:2010/ BTNMT. Nc thi tip tc c kh trng bng ha cht nh do, ozon...Cc cng trnh XLNT BV c thit k theo cc nguyn tc:Tit kim din tch t xy dng: Cng trnh c xy dng bng b tng ct thp ton khi, lp t sn bng thp hoc vt liu composit chu c tc ng c hc. Vic xy dng hp khi cc cng trnh to iu kin d vn hnh cng nh thu mi x l, bo m cnh quan trong khu vc BV v khu dn c. i vi cng trnh xy dng bng b tng ct thp, nhit nc thi trong c n nh, m bo tt cho cc qu trnh x l sinh hc din ra. Cc cng trnh cng c thit k m bo ch t chy v hn ch n mc ti a vic s dng my bm v cc thit b cp thot nc khc.Moun ha cc cng trnh x l nc thi: H thng XLNT phi x l c lng nc thi hin nay cng nh m bo vn hnh n nh trong tng lai khi lu lng nc thi tng. V vy, cc cng trnh XLNT chnh (cc cng trnh x l sinh hc) c thit k thnh cc n nguyn. T hp cc cng trnh thnh dng modun, ph hp vi vic pht trin cng sut.Hn ch mi nc thi: Mi nc thi ch yu hnh thnh ti trm bm, ngn x l hiu kh, ngn cha bn... Cc cng trnh XLNT c y kn bng np b tng ct thp hoc np thp khng g. Ti cc cng trnh to mi hi b tr chp ht v qut ht a kh thi v x l bng than hot tnh ti b lc hp ph hoc b lc sinh hc trc khi x ra mi trng. Xung quanh trm XLNT c trng cy to cnh quan cng nh hn ch bc mi.Cc cng ngh v cng trnh XLNTHin nay, ti cc BV v c s y t nc ta ph bin cc cng ngh v cng trnh XLNT:Cng trnh lc sinh hc nh git: B lc sinh hc dng XLNT bng phng php sinh hc hiu kh mc hon ton hoc khng hon ton. B hot ng theo nguyn tc vi sinh vt dnh bm trn vt rn v hnh thnh mng lc sinh hc. B c cp gi t nhin hoc cp gi nhn to. i vi b lc sinh hc nh git, BOD5 ca nc thi a vo b lc sinh hc khng c ln hn 200mg/l, ti trng thy lc q ly - 3 m3/m3 vt liu/ ngy.c im dy chuyn cng ngh XLNT c b lc sinh hc nh git l: Khng cn hi lu bn t b lng th cp v b lc; Khng cn my thi kh. Bn hot tnh tp hp cc loi vi sinh vt XLNT. Cc loi vi khun hiu kh tch t trong cc bng bn (sinh trng l lng) s hp th v s dng oxy c bo ha trong nc oxy ha cht hu c. Cc thng s cng ngh c bn ca b bn hot tnh (b aerotcn) l Hu lng bn hot tnh ph hp vi ti lng hu c tnh theo BOD v lng khng kh cp cho qu trnh. Bn hot tnh t b lng th cp c hi lu thng xuyn v b aeroten.Cc cng trnh XLNT hp khi: Do nc thi BV v cc c s y t, ngoi hm lng cht hu c cao, lng nit amoni cng rt ln, mt khc lu lng nc thi cn x l nh nn hin nay ngi ta thng tch hp cc qu trnh XLNT trong cc modun dng b b tng xy ti ch hoc ch to sn bng cc loi vt liu composite ct si thy tinh (FRP), thp khng g... B hot ng theo nguyn tc AO (thiu kh - Anoxic v hiu kh - Oxic). V vy ngoi vic x l hu c, cc qu trnh x l sinh hc tch hp trong cc b ny cn x l c nit thng qua qu trnh nitrat ha v kh nitrt. S cc qu trnh XLNT tch hp trong b x l sinh hc theo nguyn tc AO c nu ti Hnh 3.Nhm tng cng hiu qu x l cng nh gim kch thc cng trnh, ngi ta thng p dng cc tin b mi v cng ngh nh dng gi th di ng vi sinh vt XLNT dnh bm v sinh trng trn hoc ng dng mng siu lc (UF) trong h MBR (Membrane Bio-Reactor) thay cho qu trnh lng th cp v kh trng.Cc loi cng trnh XLNT hp khi hin nay ang c ng dng XLNT BV l cc b johkasou ca Nht Bn, b bioast... vt liu FRP hoc b CN2000.V69... bng thp.Cc cng trnh x l sinh hc nc thi BV trong iu kin t nhin (Dewat): y l mt trong nhng phng php XLNT truyn thng cho hiu qu tng i cao vi chi ph qun l thp. Cng ngh ny s dng cc qu trnh x l ln men k kh v hiu kh trong iu kin t nhin m khng c cc qu trnh cung cp kh cng bc. Kh c cp cho cc h vi sinh vt trong h thng x l thng qua qu trnh lm thong t nhin trong cc h sinh hc cng nh cc bi lc ngp nc c trng cy.c bit vi cng ngh x l k kh bng b t hoi ci tin c vch ngn mng dng hng ln gip nng cao hiu sut qu trnh x l. S h thng Dewats c nu ti Hnh 4.Bi lc ngp nc XLNT gm hai dng: ngp nc b mt v ngp nc pha di (bi lc ngm), thng p dng i vi vng t ct pha v st nh x l sinh hc hon ton nc thi sau khi c lng s b. Cc bi lc ngp nc thng c trng cy pha trn nn thng c gi tt l bi lc trng cy.Mi loi cng ngh v cng trnh XLNT u c cc u, nhc im ring. Tng hp cc u, nhc im c nu ti Bng 1.Cc cng trnh XLNT nu trn c th ng dng trong cc iu kin ph hp. Cc cng trnh hp khi nh b johkasou, thp lc sinh hc nh git... d ng dng cho cc trm XLNT BV khu vc th khi yu cu nc thi sau x l p ng yu cu mc A ca QCVN 28:2008. Ngc li, h thng XLNT theo nguyn tc phn tn (Dewat) thng dng XLNT cc c s y t quy m nh, vng nng thn.TCMT 08/2013