Bn hot tnh v s dng bn hot tnh trong x l nc thi1. Bn hot tnh - vi sinh vtBn hot tnh l nhng qun th sinh vt, vi sinh vt bao gm: vi khun, nm, Protozoa, tch trng v cc loi ng vt khng xng, ng vt bc cao khc (giun, di, b). Bn c dng bng, mu nu xm.Vai tr c bn trong qu trnh lm sch nc thi ca bn hot tnh l vi khun c th chia lm 8 nhm sau:1. Alkaligenes - Achromobacter2. Pseudomonas3. Enterobacteriaceae4. Athrobacter baccillus5. Cytophaga - Flavobacterium6. Pseudomonas - Vibrio aeromonas7. Achrobacter8. Hn hp cc vi khun khc; Ecoli, MicrococusNgun dinh dng cho nhng vi sinh vt, sinh vt l nhng cht bn hu c. So vi sng, h t nhin, th qun th trong b bn hot tnh khng a dng bng; c th l: hon ton khng c to, giun, b v cc loi h ng th ngho hn. Ring v qun th vi sinh vt th bn hot tnh rt a dng. Vi khun l nhng nhm vi sinh vt quan trng nht trong vic phn hy cc hp cht hu c v l thnh phn cu to ch yu ca bn hot tnh. Bn cht ca hp cht hu c trong nc thi s xc nh loi vi khun no l ch o. Nc thi cha protein s kch thch cc loi Alcaligenes, Flavobacterrium v Bacilus pht trin. Trong khi , nu nc thi cha hydrat cacbon hoc cacbua hydro th kch thch Pseudomonas. C thi k ngi ta cho rng, bn hot tnh to nn do vi khun v Zoogloea ramigen. Nhng sau, ngi ta ch rng tt c cc loi vi khun ng vai tr chnh, cn Zoogloea Ramigera ng vai tr chnh, cn Zoogloea Ramogera ng vai tr ph i vi thnh phn bn hot tnh.Nm thng c coi l khng mong mun tn ti trong bn hot tnh. Nhng i khi iu kin nht nh vn thy c nm tn ti. Nu nc thi cha hydrocacbon, vi nng cao, hoc c cht hu c l, pH thp, thiu cht dinh dng th s kch thch nm pht trin. a s loi nm c xu hng to dng ch v ngn cn vic to bng v lm bn kh lng. Mt vi loi nc thi cng nghip to nm khng phi nh Fusarium, l loi nm to bn c kh nng lng bnh thng.Protozoa ch ng vai tr gin tip trong vic n nh - phn hy cht hu c m thi. Khi nng cht hu c thp to iu kin cho ng vt nguyn sinh pht trin v chim ch o trong bn hot tnh. Khi nhiu qun th vi khun bi t do s kch thch Ciliates bi t do. Khi qun th vi khun tr nn ngho, Ciliates bi t do li nhng ch cho Ciliates tim mao pht trin.Rotifers thng t thy trong bn hot tnh. Chng ch pht trin chim ch o khi cc loi Protozoa khc ngho. Chng c th n cc mu bng bn ln. V vy loi Rotifers c coi l loi ch th cho bit h sinh hc n nh ri.C s l thuytBn hot tnh c hnh thnh rt n gin bng cch lm thong sc kh vo nc thi vi s c mt ca vi khun. Vic sc kh c thc hin cho ti khi vi khun phn hy cht hu c. Bn hot tnh hnh thnh khng phi bi mt loi vi khun to bng bc bit m ch l mt hin tng bnh thng, bi mt loi vi khun u c mc nng lng nht nh. nghin cu l thuyt c s, tt nht l bt u vi nc thi th mi, trc khi bn pht trin v theo di qu trnh qua tng giai on.C th to bn hot tnh t nc thi cha nhiu keo nh nc thi sinh hot, hoc nc thi cha nhiu cht tan phc hp nh nc thi nh my ha cht tng hp. S hnh thnh bn hot tnh u din ra nh nhau khi tin hnh hai loi nc thi trn y, min l bo m n nh v c cht dinh dng, tc l cha y cc nguyn t dinh dng cn thit cho vi khun pht trin bnh thng. a s nc thi cha vi sinh vt sn ra bn hot tnh, khng cn phi gieo cy g thm. Nhng vi sinh vt ny thng c xut x t phn, cc cht bn sinh hot. i vi mt s t nc thi cng nghip c th phi c thm mt t phn gieo cy.Khi bt u lm thong, t l thc n v vi sinh vt (F:M) rt cao nn vi sinh vt trng thi d thc n. S sinh trng ban u theo qui lut Logarit. Khi vi khun bt u pht trin th Protozoa cng bt u pht trn. Trong sut pha sinh trng Log, cht hu c trong nc thi b kh vi tc cao nht - max, vi s chuyn ha ti u ca cht hu c thnh t bo mi. Mc nng lng cao gi cho tt c vi sinh vt tn mn hon ton, c th cha c c bn hot tnh ngay, chng no vi sinh vt cn ang trong pha sinh trng log. Tc trao i rt nhanh ca vi khun lm cho nhu cu tiu th oxy rt cao. Nu khng gi c iu kin hiu kh, tc l khng m bo oxy ha tan, th tc trao i s khng theo qui lut log, nhng vn theo cp s cng cho n khi oxy khng cn l yu t gii hn na. Protozoa s b nh hng ngc li nu iu kin ym kh c ko di mi.T l thc n - vi sinh vt (F:M) gim rt nhanh v thc n b cn v nhng t bo mi li sinh sn ra. Ti mt thi im nht nh, thc n ch va v l yu t gii hn trong vic sinh trng tip theo. Pha sinh trng log bt u chuyn sang pha sinh trng chm dn. S sinh trng tip theo t l thun vi thc n cn li. C vi khun ln Protozoa u bt u gim. Mt t t bo bt u cht v bt u hnh thnh bng keo t. Trong b aeroten chy ri, nhng vi khun thng xuyn tip xc vi nhau. Chng no vi khun c nng lng th chng phn hy cng nhanh v tip tc chc nng trao i bnh thng ca chng. Khi nng lng ca h gim, cng nhiu vi khun b thiu nng lng khc phc lc hp dn gia hai t bo, ngay tc khc chng lin kt keo. Hai t bo chuyn ng nh mt, chng bao lu ba ri bn... C nh th cho ti khi ht nh dng bng c hnh thnh.Nng thc n tip tc gim v vi sinh vt tip tc tng, nhng vi tc chm dn. T l F:M tr nn nh nht, kt thc pha sinh trng chm dn v bt u pha h hp ni bo. T l F:M c gi khng i trong sut pha h hp ni bo. C th ni h rt n nh pha h hp ni bo. Ch c mt lng rt t thc n cn li khng b phn hy (trao i) hoc b phn hy vi tc rt chm. Nhu cu tiu th nng lng gi cho vi khun sng rt thp so vi nng lng tiu th cho sinh trng.Vi khun khng th c nng lng t phn thc n cn li trong nc bao quanh chng, nn chng bt u phn hy phn thc n d tr trong t bo ring ca mnh. M d v hydratcacbon b tiu hao trc v sau l protein. Mc nng lng va gim th tc to bng li tng rt nhanh. Nhng loi Protozoa gi tc bi t do phi vt v mi tm c vi khun sinh sng v chng cng bt u cht. Khi , loi Protozoa c chn bt u pht trin v chng chim v tr ch o trong sut pha trao i ni bo. Vi khun bt u cht nhin hn. Enzyme ni bo ca chng tan rt nhanh trong thnh t bo, cht dinh dng (cn li trong t bo) khuch tn ra ngoi cung cp mt cht thc n na cho cc t bo khc cn sng st. Khi nim cho rng vi khun n nhau l khng c l. Cht nhy cho php vi khun cn sng ly c cht dinh dng t vi khun cht bn cnh, nhng ch sau khi t bo cht. Vn quan tm na l: phn cn li ca vi khun l phn bn vng, khng phn hy c, l hp phn khng nhy ni bo. Cht ch yu cu to nn thnh t bo phi l hp cht nhy polysaccarit th cng c th phn hy mng t bo v lp mng nhy cng l sn phm thi ca thnh t bo. Vi khun phi va to ra va phi cha enzyme , nn chng c coi nh mt bnh cha mui ton nng.Nu thi gian lm thong c tip tc th qun th vi khun s tip tc gim. Loi Protozoa gi tc bi t do cng cht ht, loi Protozoa c chn tim mao cng bt u gim, nhng tch trng Rotifers li bt u tng. Tch trng Rotifers c th n nhng ht bng keo t nh m khng ty thuc nhng t bo c th. Nu thi gian lm thong rt di th lm cho tt c mi loi sinh vt u cht v ch cn li phn tr bn vng ca t bo. Khng bao gi c php lm thong bn hot tnh qu lu v phi mt nhiu thng mi t c trng thi hot tnh ban u.Thng thng khi t c ti pha h hp ni bo th phi tch bng bn hnh thnh bng cch lng. Bng m c li c tun hon nui dng b bn hot tnh giu cht hu c. V lng vi sinh vt cao hn lc ban u nn t l F:M thp hn v vi khun li bt u pht trin nhng im cao hn trong chu trnh sinh trng. Thi gian lm thong khng i s cho php h c tng tin dn n pha h hp ni bo theo tng chu trnh. Kt qu s to c bng tt hn v nc ra khi h trong hn. Nh vy tc kh cht hu c s nhanh nht pha sinh trng, cn vic to bng bn s tt nht pha h hp ni bo.2. B bn hot tnh trong x l nc thiB bn hot tnh l mt cng trnh lm sch sinh hc in hnh nht v c tnh "nng ng" nht. N c th cho php u chnh nc ra vi bt k nng cht bn hu c m ta mong mun - t nng cao n nng thp.Qu trnh x l bng bn hot tnh c pht trin cc nc t u th k 20, n nay c nhiu thay i c bn v hon chnh, pht trin theo chiu hng nghin cu, thit k cu to v qun l.Khng c cng trnh x l sinh ha no nhiu u im cng nh nhiu nhc im hn so vi b bn hot tnh.2.1. Nguyn l cng tcB bn hot tnh l b bn c hnh ch nht di trn mt bng. Nc thi chy vo b c ha trn vi bn hot tnh tun hon. cung cp oxy cho vi sinh vt - bn hot tnh v khuy trn u hn hp, ngi ta dng thit b khuy trn bng khng kh nn hoc c kh.Thng thng khng kh nn c dn vo mt pha ca b. Nc vo u b v ra cui b. C khi ngi ta dn v phn phi nc dc theo cnh di v dn ra theo cnh i din - gi l b aeroten trn. Thi gian nc lu li trong b thng t 2 n 12 gi, i khi 20 gi.Cc cht bn trong nc thi s hp ph ln b mt bn hot tnh. Cng qu trnh hp ph rt mnh, nht l nhng pht u sau khi nc thi tip xc vi bn. Trong thi gian , nng nc thi gim xung qu na. Nhng cht hu c dng tan chuyn vo trong t bo vi khun nh men permeaza. , cc cht bn c phn gii v ti to cht mi ca t bo. Nhng cht hu c c kch thc phn t ln s nh tc dng ca men ngoi bo v phn chia thnh nhng phn t nh hn xm nhp vo t bo. Trng thi bn hot tnh, thnh phn tnh cht nc thi, t l gia nng cht bn v nng bn hot tnh v.v... nh hng n lng v t l gia cc cht hp ph trn b mt t bo v cc cht hp ph vo trong t bo.Cc cht l lng khng tan trong nc cng hp ph ln b mt t bo - bn hot tnh. Mt phn nhng cht ny cng vi vi khun l thc n cho Protozoa, giun b. Mt phn khc chu tc dng bi men vi khun bin thnh cht tan v c vi khun ng ha. V qu trnh khong ha cc cht l lng din ra chm hn so vi cc cht tan, cho nn trong thnh phn ca bn hot tnh bao gi cng cn mt lng nht nh cht l lng cha kp chuyn ha, phn gii.Sau khi ra khi b bn hot tnh, hn hp nc v bn qua b lng hai. bn hot tnh ng t li v lng xung. Nc trong - sch, cha rt t cht hu c, sau khi c kh trng s x ra ngun nc sng h. Bn hot tnh lng xung, phn ln c tun hon tr li b bn hot tnh, mt phn gi l bn hot tnh d c tip tc a i x l.Phi cho bn hot tnh tun hon tr v v phi gi nng bn trong b bn hot tnh mc n nh, ch x i lng bn d - tng ng vi lng tng sinh khi - khng cn thit cho qu trnh m thi.Bn hot tnh lng xung b lng hai cn cha kh nhiu cht cha c chuyn ha. Trc khi tun hon v b bn hot tnh, ngi ta cho ti sinh.Ti sinh bn hot tnh bao gm lm thong - sc kh vo bn m khng cho thm cht bn vo na. Khi cc cht hu c hp ph v hp ph cha kp chuyn ha trc y th lc ny s b oxy ha. Khi nc thi cha cc cht chm oxy ha, tc l cha cc cht bn vng th cn phi thc hin ti sinh v khi s tit kim c nhiu dung tch chung ca b bn hot tnh, trnh c hin tng ym kh trong b. Do vy ngay c khi nc thi cha cc cht d b oxy ha nn ngi ta cng thc hin ti sinh. b ti sinh, nng bn rt cao, ti 4 - 8 g/l gp 3 - 4 ln nng bn hot tnh b bn hot tnh (1,5 - 2,5 - 3g/l).Ngi ta c th lm sch nc thi vi mc hon ton hoc khng hon ton. Lm sch hon ton tc l trong b din ra c hai qu trnh hp ph v oxy ha. Nc thi sau khi ra khi b lng hai c nng BOD ton phn rt thp < 15 - 25mg/l. Nu vt qu gii hn v ch din ra mt giai on hp ph thi th gi l x l khng hon ton. Kiu b bn hot tnh, ch cng ngh, thnh phn ha hc ca nc thi... u nh hng ti s hnh thnh bn hot tnh - cc qun th vi sinh vt trong b.2.2. L thuyt vn hnhTrong h bn hot tnh, b bn hot tnh c kch thc c nh, khi c thi gian m thong cng c nh ng vi lu lng nc cho. Nh vy, thi gian t hot tnh sinh hc s b gii hn theo s bin i lu lng dng chy trong b. Vi nc thi sinh hot, b bn hot tnh c thit k vi thi gian trung bnh nc lu li trong v ti trng trung bnh gBOD/m3 b trong ngy m. Vi thi gian trung bnh, vi sinh vt s bin i theo chu k mt cch lin tc dc theo ng cong sinh trng.Khi bn tun hon c khuy trn vi nc thi, t l F:M s quyt nh thi gian m vi sinh vt lp li ng cong sinh trng. Thi gian nc lu li trong b bn hot tnh s xc nh thi gian phn ng din ra dc theo ng cong sinh trng. Vi ti trng cht hu c t 0,3 - 0,5kgBOD/mng v thi gian nc lu li 6 - 8gi vi sinh vt s pha sinh trng chm dn trong 2 gi, thi gian cn li l pha oxy ha ni bo. Pha oxy ha ni bo vi thi gian di s cho php h thng lm vic tt. Nc ra khi b bn hot tnh s d lng, cha t cht hu c, nhng li hn ch h khi phi lm vic vi ch ti trng tng t ngt.Mt trong nhng chng ngi i vi b bn hot tnh l khng n nh ca nc vo: Qu trnh vn hnh b nng n nht khi lu lng nc thi v ti trng cht bn hu c bin ng ln. V l do ny cho nn b bn hot tnh ch c p dng i vi cc th ln, ni c s n nh tng i v lu lng v nng cht bn. nhng b bn hot tnh thng vi sinh vt phi chu ng s khng n nh v nhng chu k dao ng ny.Khi vi sinh vt t ti cui giai on lm thong, chng s trng thi cn bng vi cht hu c bao quanh. thi im ny, s sinh vt sng t l thun vi lng cht hu c trong nc. Trong bn hot tnh ngi ta nh gi rng ch khong 25- 30% cht l lng khng tro trong thnh phn cu to ca vi sinh vt sng. Phn cn li ca cht hu c khng tro l cht hu c tr bn vng, v xc t bo cht ln vi nc ra. Tun hon bn lng v u b bn hot tnh s tng lm tng tc thi t l F:M v kch thch vic tng hp nhanh chng cc t bo mi. Vi sinh vt li trao i v phn hy cht hu c, ng thi li phc hi s cn bng.Vi chu k bnh thng ca nc sinh hot, lu lng v nng thp v ban m v tng ln v ban ngy. Ngha l vi sinh vt ko di thi gian trao i ni bo v ban m v khng c chun b tip nhn s tng t ngt ti trng cht bn hu c m li gim thi gian nc lu li lc bui sng sm. Kt qu l lm gim hiu sut qu trnh. Ban ngy, lu lng, nng tng ln, thi gian trao i b gim vi gi tr min - thp nht. Kch thc ca b phi cho php vi sinh vt t c v thc hin giai on trao i ni bo.Trong sut khong thi gian m lu lng v ti trng cht hu c cao nht (max), nu b bn hot tnh khng ln giai on din ra th lu lng nc ra khi b s c v ln nhiu vi sinh vt. S dao ng thng xuyn v s khng cn bng lin tc ca vi sinh vt l vn c bn cn lu thit k, vn hnh c hiu qu h thng b hiu kh vi bn hot tnh.Nhu cu oxyQu trnh vi bn hot tnh l mt qu trnh hiu kh, yu cu c oxy d t nht 0,5mg/l trong sut thi gian, bt k thi im no nu nh h hot ng lin tc. Nu h bin thnh ym kh th s c hi cho Protozoa, v Protozoa li cn thit cho vic lm trong nc. Nh vy phi ko di thi gian cn thit cho qu trnh n nh din ra. Oxy l yu t khng ch u tin trong h vi bn hot tnh. Nhu cu oxy l hm s thun ca qu trnh trao i sinh hc. Nhu cu oxy ln nht u b aeroten khi thc n v vi sinh vt khuy trn vi nhau. Nu nhu cu oxy ln hn lng cung cp th s to iu kin ym kh v vn vn hnh s tr nn phc tp hn. Nng oxy ha tan thp s lm cho nc ra khi h b c. Protozoa khng pht trin c ha tan chc nng ca mnh; vi khun dng ch s pht trin, ngn cn vic to bng mn v lng km. cung cp oxy ngi ta dng h phn phi khng kh bng my nn hoc c kh. x l nc thi sinh hot, khi lng khng kh cn cung cp khong 4 - 8m3 khng kh cho 1m3 nc thi vi hiu sut vn chuyn oxy khong 5%. h lm thong vi dng my nn kh, khng kh nn c phn phi qua ng khoan l hoc qua tm xp. Oxy t cc bt khng kh s c khuch tn vo nc, ri vo bng bn v vi sinh vt. Tc chuyn vn oxy ty thuc gradien nng oxy gia bt kh v nc, din tch tip xc gia nc v kh, thi gian tip xc, nhit v c tnh ca nc... Tc vn chuyn oxy ln nht khi nng oxy trong nc bng 0. Tuy nhin trong b bn hot tnh khng c ni no nng oxy bng 0 c.Din tch tip xc gia khng kh v nc s tng khi kch thc cc bt kh gim, cho nn cc bt kh cng nh th s chuyn vn oxy s cao hn so vi cc bt kh ln. Nhng mt khc, cc bt kh cng nh th sc khng i vi s chuyn vn oxy t kh sang nc ( bin gii phn chia) li tng thm. Oxy khuch tn t bt vo nc, bo ha mng nc quanh bt. Tip nh dng chy ri v ty thuc bo ha, cc mng nc quanh bt s i ch cho nhau v cui cng bt kh ni ln mt nc ri bung ra. Bt kh ni ln pha mt nc rt nhanh nn thi gian tip xc vi nc rt ngn, s vn chuyn oxy vo nc s t hn so vi nhng bt cng kch thc nhng ni ln chm. Thi gian tip xc c th tng (hoc gim) khi gim tc (hoc chiu cao) ni ln ca bt. Nhng nu gim qu nhiu v tc ni ln ca bt th s lm gim khuy trn ca hn hp v to nn nhng vng cht trong b.Nhit tng s lm gim ha tan oxy trong nc, nhng li tng tc vn chuyn oxy v n nh hng ti nhng c im khc ca qu trnh vn chuyn oxy.c tnh ha hc ca nc nh hng ti nhiu s vn chuyn oxy. Nng mui hoc cc cht hu c cao th s lm gim tc chuyn vn oxy. Bn thn nc thi cng lm chm s chuyn vn oxy. Ngy nay trong nc thi cha nhiu cht ty ra - hot tnh b mt, cng nh hng nhiu ti s chuyn vn oxy. Nhng nc thi, cht ty ra tng hp khng lm gim tc chuyn vn oxy nhiu hn so vi cc hp phn hu c khc. Vn ny v ang c nghin cu.Nh vy hiu sut chuyn vn oxy u b, ni nc thi v bn bt u xo trn vi nhau, s thp hn khong sau mt t, khi mt phn cht hu c b trao i - phn hy. Khi nhu cu oxy gim th hiu sut chuyn vn oxy cng gim. ni din ra giai on h hp ni bo nhu cu oxy rt t, hiu sut chuyn vn oxy s thp.Nhu cu cht dinh dng v nhng yu t khcTrong tt c cc h x l nc thi bng phng php sinh hc, u cn phi cung cp cc nguyn t dinh dng cho vi sinh vt chng xy dng t bo. Nc thi sinh hot cha cc nguyn t m vi khun cn. Nhng nhiu loi nc thi cngnghip thiu cc nguyn t ti cn thit. l Nit, Photpho. Lng cn thit ca cc nguyn t ny c th tnh c theo tng iu kin c th.Cc yu t mi trng quan trng l: pH, nhit v th oxy ha - kh.Khong gi tr pH = 6,5 - 9 c coi l bnh thng i vi h bn hot tnh. Nu di 6,5 th nm bt u pht trin v pH = 4,5 th nm lm ch hon ton. Nu trn 9 th tc trao i cht s b chm v ngng.Th nng oxy ha kh l th nng gia nhng tc nhn oxy ha v kh, cha k ti lng ca tng loi cht hoc tnh sinh hc ca chng. Gi tr th oxy ha kh rt quan trng i vi vic vn hnh h thng. N khng phi l nguyn nhn m l kt qu ca phn ng sinh hc.Ngy nay ngi ta nghin cu p dng rt nhiu loi hnh v cu to cng nh s cng ngh ca b bn hot tnh nh: b bn hot tnh kt hp lng hai, b bn hot tnh vi b ti sinh ring bit bn hot tnh, b bn hot tnh nhiu bc - x l trit ti hai giai on nitrat ha v kh nitrat...2.3. Cc qu trnh sinh hcQu trnh sinh hc xy ra qua 3 giai on:+ Giai on 1: Bn hot tnh hnh thnh v pht trin. Lc ny, c cht v cht dinh dng ang rt phong ph, sinh khi bn cn t. Theo thi gian, qu trnh thch nghi ca vi sinh vt tng, chng sinh trng rt mnh theo cp s nhn, sinh khi bn tng mnh. V vy, lng oxy tiu th tng dn vo cui giai on ny rt cao. Tc tiu th oxy vo cui giai on ny c khi gp 3 ln giai on 2. Tc phn hy cht bn hu c tng dn.+ Giai on 2: Vi sinh vt pht trin n nh, hot lc enzym t Max v ko di trong thi gian tip theo. Tc phn hy cht hu c t Max, cc cht hu c b phn hy nhiu nht. Tc tiu th oxy gn nh khng thay i sau mt thi gian kh di.+ Giai on 3: Tc tiu th oxy c chiu hng gim dn v sau li tng ln. Tc phn hy cht bn hu c gim dn v qu trnh Nitrat ha amoniac xy ra. Sau cng, nhu cu tiu th oxy li gim v qu trnh lm vic caa Aerotank kt thc.

2.4. Cc h thng b bn hot tnhH thng b bn hot tnh gm cc loi: b bn hot tnh truyn thng, b bn hot tnh tip xc - n nh, b bn hot tnh thng kh ko di, b bn hot tnh thng kh cao c khuy o hon chnh, b bn hot tnh chn lc...

+ B bn hot tnh truyn thng: B bn hot tnh dng truyn thng u tin c s dng l cc bn hiu kh di, hp. Lng oxy cn dng thay i dc theo chiu di ca b phn ng sinh ha. Do , h thng ny s dng cc thit b thng gi lm thong b mt lng oxy cung cp ph hp vi nhu cu s dng dc theo chiu di b. B phn ng thng c dng hnh ch nht, vi dng vo v tun hon bn hot tnh i vo b 1 u v cht lng trong b c ha trn (dng thi) s i ra u i din. M hnh dng chy gn ging nh h thng dng chy u, vi s phn b thi gian lu cht ph thuc vo t l chiu di v chiu rng ca bn cha, hn hp trong b gm oxy do thit b cung cp, cc cht nn c sn trong dng vo v dng ra.Lng gi cp vo t 55m3/1kg BOD5 n 65m3/1kg BOD5 cn kh. Ch s th tch bn thng dao ng t 50 - 150ml/g, tui ca bn thng t 3 - 15 ngy. Nng BOD u vo thng < 400mg/l, hiu qu lm sch thng t 80 - 95%.+ B bn hot tnh tip xc n nh: H thng ny chia b phn ng thnh 2 vng: vng tip xc l ni xy ra qu trnh chuyn ha cc vt cht hu c trong nc thi u vo, v vng n nh l ni bn hot tnh tun hon t thit b lc nc sc kh n nh vt cht hu c. Do nng cht rn l lng trong nc kh cao trong b n nh (tng ng vi nng bn hot tnh tun hon), tng th tch b phn ng sinh ha (vng tip xc v n nh) c th nh hn, ging nh loi b bn kiu truyn thng, trong khi vn duy tr thi gian lu bn nh c. V vy, b bn loi ny c s dng c th va lm gim th tch b phn ng, hoc c th lm gia tng kh nng lu cha ca b bn truyn thng.Trong vng tip xc, thi gian tip xc t 20 - 60 pht (ph thuc lu lng dng vo). Dng bn ti sinh thng chim 25 - 75% dng nc thi u vo x l. Th tch ca vng n nh chim 50 - 60% tng th tch ca ton h thng, vi thi gian lu nc thng t 0,5 - 2 gi, trong khi th tch vng tip xc l 30 - 35% tng th tch chung, vi thi gian lu nc l 4 - 6 gi ty thuc vo dng bn hot tnh tun hon. Hiu qu x l ca h thng ny thng t 85 - 95% kh nng loi b BOD5 v cc cht rn l lng khi nc thi x l.B bn tip xc - n nh thng c dng trong x l nc thi sinh hot vi s lng ng k cc hp cht hu c di dng cc phn t cht rn.Hnh 3: B bn hot tnh tip xc n nh+ B bn hot tnh thng kh ko di: Thng c thi gian lu bn ko di n nh lng sinh khi rn t qu trnh chuyn ha ca cc vt cht hu c b phn hy bi vi khun. Thi gian lu bn thng ko di t 20 - 30 ngy, ng ngha vi vic cn thi gian lu nc khong 24 gi duy tr kh nng pha trn nng cc cht rn l lng trong nc. Thi gian lu nc ko di c 2 tc ng: lm gim lng cht rn b loi b v lm tng s n nh ca qu trnh. Tuy nhin, i vi b phn ng loi ln th yu t ny s gy mt s bt li, l lm hn ch kh nng pha trn.Hnh 4: B bn hot tnh thng kh ko di+ B bn hot tnh thng kh cao c khuy o hon chnh: B hiu kh c tc thng kh cao v khuy o hon chnh l loi Aerotank tng i l tng x l nc thi c nhim cng nh nng cc cht l lng cao. Aerotank loi ny s c thi gian lm vic ngn. Rt ngn c thi gian thng kh bng vn hnh t s F/M cao, gim tui th bn hot tnh (thi gian lu nc trong b ngn). Trong b Aerotank khuy o hon chnh, nc thi, bn hot tnh, oxy ha tan c khuy trn u, tc thi. Do vy, nng bn hot tnh v oxy ha tan c phn b u mi ni trong b v dn n qu trnh oxy ha c ng u, hiu qu cao.u im ca cng ngh ny l:- Pha long ngay tc khc nng cc cht nhim bn, k c cc cht c hi (nu c).- Khng xy ra hin tng qu ti cc b mt ni no trong b.- Thch hp cho x l cc loi nc thi c ti trng cao, ch s th tch bn cao, cn kh lng.Hnh 5: B Aerotank thng kh cao c khuy o hon chnhDa trn nguyn l lm vic ca Aerotannk khuy o hon chnh, ngi ta thay khng kh nn bng cch sc oxy tinh khit. B phn ng thng c nhiu ngn, kn, v cung cp cc dng nc giu oxy dng kh ha trn trong cht lng. Dng nc thi vo v dng bn hot tnh tun hon ch c a vo ngn u tin cng vi oxy (thng tinh khit 98%). mi ngn c s pha trn hon ton trong tng . S pha trn cc cht rn l lng v oxy ha tan c cung cp cho mi ngn. Cc loi my mc s dng trong loi b ny l: my thi kh b mt tc nh v tuabin t trong nc. Vic s dng ngun oxy c tinh khit cao s c tc dng lm gia tng p sut oxy tham gia trong mi ngn, v vy s lm tng t l chuyn ha th tch oxy hn so vi h thng s dng khng kh. iu ny s lm cho th tch b phn ng sinh ha cn s dng nh li, v vy thi gian lu nc ch cn khong 2 - 4 gi. Thi gian lu bn ti thiu t 1 - 2 ngy thng c s dng x l nc thi sinh hot, cn i vi nc thi cng nghip cn thi gian lu bn di hn.+ B bn hot tnh chn lc: B bn hot tnh ny ch mi c pht minh gn y, c dng kim sot s tng trng qu mc ca cc vi khun ln men, c th gm cc loi gy hi. N cung cp iu kin mi trng c li cho s tng trng ca cc vi sinh vt kt bng, kt qu l lm gia tng kh nng lng ng ca bn hot tnh. B bn hot tnh chn lc s dng 2 c ch chn lc cc vi sinh vt: ng hc v trao i cht. B bn hot tnh chn lc thng chia thnh tng khi th tch nh, cha trong cc ngn ring bit. Dng chy xung t b phn ng c th c pha trn hon ton hay ch l dng chy kn.