2. The necessity to remove BOD, ammonia, nitrates and phosphorus from waste water

Transcription

1 Professor Navarro B-tech level : Biological treatment of waste water and sludge Figure 1 illustrates the water cycle in town ; in this course, we will study biological treatment applied to waste water and sludge purification, not to drinking water production. 1. Municipal waste water quality and discharge standard MWW quality is rather constant ; this board illustrates the average chemical composition od MWW and the discharge standard ( from Pollution control acts, rules and notifications issues thereunder, Central Pollution Control Board, May, 1998) Parameter unit Average value Discharge standard in inland surface water ph 7.5 to to 9 Suspended Solids SS mg / l 150 to BOD 5 mgo 2 /l 100 to COD mgo 2 /l 300 to 1, NH 3 mgn/l 20 to TKN mgn/l 30 to Nitrate NO 3 mgn/l <1 10 P mgp/l 10 to The necessity to remove BOD, ammonia, nitrates and phosphorus from waste water This board summarizes the origin and the toxicity linked to the presence of various chemicals in MWW. Undesirable compound C Origin in MWW Toxicity or inconvenient for the receiving water SS Wastes Turbidity, consumption of oxygen Organic carbon : BOD 5 Organic matter Consumption of O 2 in the medium Ammonia Organic nitrogen Nitrates Phosphorus Ammonification of urea, proteins Proteins, urea Absent in MWW Present in water after nitrification of ammonia Organic matter and washing powders Consumption of O 2 Toxic for fauna Eutrophication 3. General considerations about biological treatment 3.1. Total removal of carbon, nitrogen and phosphorus

2 MWW are biodegradable : - the ratio COD / BOD, called biodegradability ratio, is inferior to 3 ; - ph is neutral ; - there are nitrogen, phosphorus, and no toxic. Bacteria will be exploited for purification of MWW. They assimilate carbon (BOD), nitrogen and phosphorus according to the mass ratio : BOD / N / P = 100 / 5 / 1. Assimilation is the intracellular incorporation of a chemical in order to carry out anabolism. However, the ratio BOD / N / P of a MWW presents a large excess of nitrogen and phosphorus ; it can be for example equal to 100 / 20 / 10. It means that a simple assimilation doesn t allow to respect the discharge standard. Two other biochemical processes should be performed in order to remove enough nitrogen and phosphorus : - nitrification, and then denitrification, for total nitrogen removal ; - specific intracellular accumulation of phosphates, for total phosphorus removal The separation between biomass and treated water. Once the metabolism is performed, the exploited microbes must be separated from treated water ; there are two techniques : attached or suspended growth. The efficiency of these two technologies depend on the bacterial secretion of an extracellular polymer : figure 2. Biofiltration is performed in one step, but is a discontinuous process : when the medium is clogged, it must be backwashed. This medium both retains SS and is the place of biological purification of MWW. Figure 3 illustrates the structure of a biofilm. Suspended growth is a continuous two-step process : biological purification and then settling in order to separate biomass from treated water. Figure 4 illustrates a biofloc structure. 4. Activated sludge and suspended growth MWW is introduced in an aerated tank : biological purification takes place and flocculating biomass grows. A real food chain develops in this tank, responsible for purification, and including a large variety of organisms : - bacteria - protozoan - metazoan. The identification of these organisms allows to check the running of the process : some organisms are indicators of the treatment quality: figures 5 to 14. Figure 15 illustrates a food chain in an aerated tank. Figure 16 illustrates the flow sheet of an activated sludge process ; as biomass grows and circulates from the tank to the clarifier, sludge must be recirculated (in order to maintain a constant biomass concentration in the aerated tank) ; the sludge draw-off allows to remove the excess of produced biomass TKN and BOD removal Organic carbon is assimilated : it provides the cell with matter and energy ; these bacteria are chemoorgano heterotrophic and aerobic ; organic matter is oxidized with O 2 and the reaction generates water and CO 2. Ammonia and phosphorus are assimilated in different biochemical ways ; in definitive, ammonia is introduced in amino acids and proteins, phosphorus in proteins, ATP, nucleic acids

3 In order to remove the nitrogen excess in MWW, nitrification of ammonia must take place in the aerated tank ; it is performed by chemo-litho autotrophic bacteria like Nitrosomonas and Nitrobacter, and generates nitrates Nitrates removal Nitrification produces nitrates, which induces eutrophication of the receiving water ; then nitrates must be removed. Chemo-organo heterotrophic bacteria carry out the denitrification : they need nitrates, but also organic matter ; oxygen inhibits the reaction : nitrates are the final acceptor of electrons and many bacteria prefer using oxygen (they can carry out both respirations). Nitrates are transformed into N 2. The process presents two characteristics : figure 17 - mixed liquor is recirculated in an upstream zone : water inlet must contain organic matter (BOD is not assimilated yet) - this zone is anoxic : oxygen inhibits denitrification Phosphorus removal The excess of phosphorus is removed by a specific metabolism, carried out by bacteria like Acinetobacter, Moraxella : figure 18 It is a two step process : anaerobiosis then aerobiosis ; anaerobiosis means neither nitrates nor oxygen, while anoxia means only absence of oxygen. Anaerobiosis step : these aerobic bacteria are stressed, they excrete a quantity Q1 of P in the medium Aerobiosis step : they incorporate a quantity Q2 of P, and Q2 >> Q1. P is finally extracted from the plant in the same time than phosphated sludge (which treatment should be aerobic). Figure 19 illustrates a plant which removes BOD, N and P from MWW Bulking Bacteria growth can present three forms : - flocculating growth, which should be obtained for activated sludge process ; - dispersed growth which occurs when the activated sludge process is started (for the first weeks, before flocculation) ; - filamentous growth, also called bulking, which occurs with dysfunctions such as presence of toxic chemical in MWW, insufficient aeration of the tank ; this type of growth cause a sharp drop in the quality of treated water due to massive entrainment of SS outside the settling tank. Figures 20 to 25 illustrates the main filamentous bacteria responsible for bulking in MWW treatment. Their identification can help to know the origin of the dysfunction. 5. Aerobic attached growth : trickling filters, biofilters, biodisks Among these three technologies, only biofiltration (figure 26) is an efficient process : it allows to remove both SS and BOD from MWW ; sometime, nitrification and denitrification can occur. Biofiltration is an expensive, discontinuous process ; it is well adapted to large variation of load, and can be implanted in specific geographic area like mountains The medium can be either sand, or granular activated carbon, or polystyrene balls on which biofilm takes place.

4 Trickling filters technology (figure 27) is quiet rare : biofilm is fixed on large pozzolan or plastic stones and SS are not removed from MWW ; it is often used as a pretreatment before activated sludge, for very concentrated industrial waste water (high BOD). Biodiscs technology (figure 28) is also rare : the biomass is attached to discs that turn around a horizontal axis and are partially bathed in raw water ; rotation brings the biomass alternately in contact with the water to be treated and the oxygen in the air. Discs are spaced 2 or 3 cm from one another and tun at 1 or 2 rpm ; they are 2 or 3 m in diameter and made of polystyrene ; they must be cover to protect them against harsh weather. This process consumes little electrical energy. A downstream clarifier retains the excess sludge. 6. Extensive processes : lagooning Natural biological purification of pollutants can occur in water : in this way, many different metabolisms are involved ; in fact, the food chain is the same as the activated sludge one but the source of oxygen is photosynthesis and not artificial aeration. The Winograsky column illustrates all the nutritional types which can occur in a layer of water : figure 29. All these natural biological reactions are exploited in lagooning ; figure30 illustrates such a two-step process : in a first microphytes lagoon, SS settle, some fermentations occur ; on the surface, algae generates oxygen which allow aerobic metabolism like BOD removal and nitrification ; the second step consists in assimilation of nitrates and phosphates by macrophytes. This technology needs a lot of space (10 m 2 / habitant). 7. Anaerobic bacterial growth for industrial waste water purification and sludge stabilization In anaerobic conditions, organic matter is reduced to methane CH 4. This natural metabolism occurs in many different places, like in deep ocean, in the ruminants rumen Because of the very slow growth of methane-producing bacteria and the cost of the industrial installation, it is applied for very high BOD load, i.e. for industrial waste water (agro-food) or for sludge stabilization in large plants Biochemistry of the process Figure 31 summarizes the different biochemical ways leading to methane : only some of these ways are used in a specific place (note that their should be competitions, for example for H 2 between acetate- producing bacteria and some methane - producing bacteria). In a digester, the following ways take place : - acetogenesis OHPA (and not the homoacetic acetogenesis) - both methanogenesis. Methane producing bacteria are archaebacteria, strictly anaerobic ; their generation time is very long (15 to 30 days) Industrial waste water purification : suspended and attached growth Figure 32 illustrates a mixed digester (suspended growth) and settling tank : Analift (Degrémont) ; the degasification device is required to remove the occluded gas, which hinders settling, from the floc. It is suitable for concentrated effluents (distilleries ). The COD load varies from 3 to 15 kg / m 3. d. Figure 33a illustrates an attached growth on a support medium : the biofilm grows on a fixed medium, through which the water passes in upflow : Anafiz (Degrémont) ; it is suitable for relatively diluted effluents such as dairies, sweet factories The COD load varies from 8 to 15 kg / m 3. d.

5 Figure 33b illustrates an attached growth on fluidized bed : Anaflux system, Degrémont. The advantages of the process are : - no risk of clogging of the support - rapid start-up -compact unit - accommodation of considerable flow variation. It is suitable for effluents from breweries, canning factories ; the COD load varies from 30 to 60 kg / m 3. d Sludge stabilization Biological sludge stabilization (reduction of the pathogenic organisms and of organic matter concentration) can be performed in three ways ; - aerobic process in a structure equivalent to the activated sludge : figure 34 - anaerobic process, number of steps depending of the load : figures 35 and 36 - composting : figure 37 Conclusion : the figure 38 summarizes all the biological processes applied to waste water treatment.

6 drinking water treatment plant DWP water table drinking water consumption end use? sludge River collective sanitation individual sanitation Sewer subsoil * sewage treatment plant STP Industries : agro-food, nuclear power plant, steel, iron and steel... Figure 1 : Water cycle in town Caption : raw water for DWP or industries municipal and industrial waste water ;* the necessity to treat industrial waste water depends on its quality and the regulation sludge

7 Bacteria secreting an Extracellular Polymer (polysaccharides, proteins ) : Zooglea ramigera, Pseudomonas aeruginosa Biofilm on a surface Biofloc in a liquid medium Attached growth : biofiltration : one step (no need to separate treated water and depolluting biomass) Raw water : biodegradable pollution Suspended growth : two steps : biological purification of raw water by the flocculating biomass then separation of treated water and biomass : Raw water : biodegradable pollution Biofilter : granular medium on which a biofilm is developing - SS removal - biodegradation ONE STEP Treated water Tank : liquid medium containing flocculating biomass : biodegradation : FIRST STEP Separation treated water / flocculating biomass : SECOND STEP Applications : - for clear water to avoid rapid clogging of the granular medium : biological treatment of drinking water production (denitrification, iron removal ) - for turbid MWW : discontinuous process : filtration, washing. Treated water Applications : - for the most famous MWW treatment process : activated sludge Figure 2 : Attached and suspended growth in water treatment

8 Biofilm particles Water flow direction Biofilm growth Biofilm death DOC adsorption Biofilm Support Figure 3 : Sketch of a biofilm (Maul A., Vagost D., Block J.C., 1989) Polymers linking microcolonies bacterium (1 to 5µm) of the colony, linked by a polymer Microcolony 13 µm 125 µm Figure 4 : Model of structure microbial floc in activated sludge

9 F ig u re s 5 to 14 : b rie f p h e n e tic c la ss ific a tio n o f mi c ro fa u n a in ac tiv a te d s ludg e T h e c o n s id e re d ta x o n o mi c h ie ra rc h y is : K ingd o m : a n im a l S u b k in gd o m B ra n c h C la ss S u b c la ss O rd e r F a mil y G e n u s S u b k in g d o m M E T A Z O A N w o rm s h y p o tr ic h s P R O T O Z O A N B ra n c h R h iz opod a F la g e lla ta C ilia ta C la ss, s u b c la ss o r ho lo tric h s p e ritric h s o rd e r M o s t fa m o u s g e n u s in a c tiv a te d s ludg e m ic ro fa u n a h e lio z o a n a m o e b ie n s th e c a m o e b ie n s Z oo fla g e lla te d Amoeba Thecamoeba P le u r o m ona s B odo, M ono s iga Paramecium, Trachelophylum L iono tu s, C h ilodon e lla Vorticella, C a r c h e s iu m, Episitylis, O p e r c u la r ia E up lo ts, A s p id is c a Rotifers, G a s tro tr ic h s Nematodes In thick letters are the organisms studied below ; for each one, are detailed : a s k e tc h a n d th e a v e ra g e s ize o f th e o rg a n is m its p h e n e tic c la ss ific a tio n th e p re d a tio n, th e h a b ita t o f th e mi c ro o rg a n is m a n d th e re la tio n w ith th e p ro ce ss m a n a g e m e n t

10 0.5 to 1 m m F ig u re 5 : S k e tc h o f a n o r ga n is m b e lo n g in g to th e c la ss o f n e m a to d e s (b r a n c h o f w o r m s ) C r o w n o f c ilia c on stitu te d b y tw o r o ta to r y d is c s. 0.5 to 1 m m M a s ta x (pha r y n x ) C u tic le T e le sc op ic bod y Spu rs F ig u re 6 : S k e tc h o f a m e ta z oa n o r ga n is m * S u b k in gd o m o f m e taz o a, b ra n c h o f w o rm s, c la s s o f r o tifer s, fifte e n k n o w n g e n u s * b a c te rio - o r p ro to z oo p h a g o u s ; p la n k to n ic o r fix e d s p ec ie s ; lo w lo a d a n d h ig h s lu d g e a g e : s a tis fy in g trea tm e n t e ff ic ie n c y a n d n itrific a tio n

11 D o rs a l fiss u r e s C ilia B e lo w v ie w L a te ra l v ie w F ig u re 7 : S k e tc h o f a p r o to z o a n o r ga n is m * c la ss c ilia te, s u b -c la ss o f h y p o tr ic h s (s e v e n k n o w n g e n u s, m a in a re E up lo te s an d A s p id isc a ) * b a c te riop h a g o u s ; a d a p te d to th e s u rfa ce o f th e flo c s, m ob ile ; lo w lo a d a n d h ig h s lu dg e 30 to 6 0 µ m

12 P e r is to m e w ith c ilia b o d y M a c r on u c le u s 30 to 60 µ m R e tr a c tile p e d u n c le 50 to 80 µ m G e nu s V o r tic e lla (th e d ia m e te r o f th e p e r is to m is s u p e r io r to th e w id e st d ia m e te r o f th e bod y ) G e nu s E p is ity lis (pa r titio n e d a n d n on re tr a c tile p e du n c le ) F ig u re 8 : S k e tc h o f a p r o to z o a n o r ga n is m * c la ss o f c ilia te, s u b -c la ss o f p er itic h s (s ix k n o w n g e n u s) * b a c te riop h a g o u s (free b a c te ria ), fix e d a t th e s u rfa ce o f th e flo c, lo w lo a d, w e ll a a e ra te d m e d iu m

13 C ilia N u c le u s A p ic a l c y to sto m 30 to 50 µ m F ig u re 9 : S k e tc h o f a p r o to z o a n o r ga n is m p e rm a n e n t in mi c ro fa u n a o f a c tiv a te d s lu dg e * c la ss o f c ilia te, s u b -c la ss o f h o lo tr ic h s, g e nu s T r a c h e loph y lu m * a d a p te d to th e s u r fa ce o f th e flo c b u t n o fix e d a n d free s w imi n g, b a c te rio - a n d p ro to z oo p h a g o u s ; h ig h c o n ce n tra tio n o f o x y g e n, m o d e ra te o r h ig h lo a d. C y to p ha r y n x (o r cy to sto m e ) C ilia M a c r o e t m ic r on u c le u s 50 to µ m F ig u re 1 0 : S k e tc h o f a p r o to z o a n o r ga n is m : P a r a m e c iu m * c la ss o f c ilia te, s u b -c la ss o f h o lo tr ic h s * b a c te riop h a g o u s ; sw im e r ; n ee d a lo t o f o x y g e n, lo w lo a d.

14 T h e qu a c on s titu te d o f silice o u s pa r tic le s 30 to 4 0 µ m F ig u re 1 1 : S k e tc h o f a p r o to z o a n o r ga n is m * b ra n c h o f R h iz o p o d a, c la ss o f T h a ec a m o e b a, g e n u s E ug ly pha * liv in g o n flo c s, n o fix e d, n o s w im e r, b a c te rio ph a g o u s (s o m e c o n s u m e fila m e n to u s b a c te ria ) ; sta b le s ludg e, lo w c h a rg e. P s e udopoda F ig u re 1 2 : S k e tc h o f a p r o to z o a n o r ga n is m : A m o e b a * b ra n c h o f R h iz o p o d a, c la ss o f a m o e b a * b a c te rio - o u p ro to z oo p h a g o u s ; liv e o n th e s u rfa ce o f flo c s ; fe w ind ic a tio n a bo u t its re la tio n w ith th e qu a lity o f th e tre a tm e n t 40 to 70 µ m

15 50 to 7 0 µ m A x o s ty la (p s e udo p od a lik e n ee d le )) F ig u re 1 3 : S k e tc h o f a p r o to z o a n o r ga n is m : H e lio z o a * b ra n c h o f R h iz o p o d a * b a c te riop h a g o u s ; ra re in s ludg e, p la n k to n ic ; lo w lo a d a n d h ig h s lu dg e.

16 F lag e lle s V a c uo le c on tr a c tile m e m b r an e c y to p la s m iq u e 10 à 2 0 µ m N o y au V a c uo le d e d ig e stio n F ig u re 1 4 : S k e tc h o f a p r o to z o a n o r ga n is m : * b ra n c h o f fla g e lla, c la s s o f z o o flag e lla te s * s w imm e r, c o n s u m e s o rg a n ic m a tte rs a n d b a c te ria ; v e r y yo u n g s lu dg e, o r a d a p te d to IWW c o n ta in ing p h e n o l

17 B a c te ria D e c o m p o s e rs H e te ro trop h s C O 2 C o n s u m e rs n : P a n d M C O 2 P rim a ry c o n s u m e r s : B, P, M C O 2 M WW in le t T a n k a e ra tio n A tm o sp h e ric d is c h a rg e F ig u re 1 5 : F oo d c h a in in a n a c tiv a te d s lu d g e a er a te d ta nk C a p tio n : B : b a c te riu m P : p ro to z o a n M : M e taz o a n

18 M W W in le t D O C, N H 3 a n d P F lo cc u la tin g b io m a ss ; b a c te ria, p ro to a nd m e ta z o a : fo o d c h a in M ix e d liq u o r M O C OH A e : DO C + O 2 C O 2 + H 2 O N itro so m o n a s a n d N itro b a c te r : C L A A e : n itrific a tio n N H 3 + O 2 NO H 2 O A c tiv a te d s ludg e ta n k A ir S lud g e re c irc u la tion F ig u re 1 6 : S k e tc h o f a s tr u c tu re o f M W W tr e a tm e n t w ith a c tiv a te d s lu d g e p r o ce ss (b io lo gy ) T re a te d w a te r S e ttlin g ta n k S lud g e e x tra c tio n

19 M W W r a w w a ter F lo w Q R e c irc u la tio n o f mi x e d liqu o r ( NO 3 - ) 2 x Q NO D O C N 2 + C O 2 M O C OH A n : d e n itr ific a tio n U p s tre a m a n o x ic z o n e M O C OH A e : DO C + O 2 C O 2 + H 2 O N itro so m o n a s a n d N itro b a c te r : C L A A e : n itrific a tio n N H 3 + O 2 NO H 2 O A c tiv a te d s ludg e ta nk A ir S lud g e re c irc u la tion F ig u re 1 7 : S k e tc h o f a s tr u c tu re o f d e n itr ific a tio n in a n u p s tre a m a n ox ic z o n e T re a te d w a te r (Q ) S e ttlin g ta n k S lud g e e x tra c tion

20

21 B a c te riu m A ce ty l C o A R e s er v e o f in tr a ce llu la r e n e r gy vo lu tin e : P o ly P i : (P i)n n P i - Q 2 R e s er v e o f in tr a ce llu la r C : P o ly C : (P H B ) + Q 1 n P i e x ter io r F ig u re 1 8 : S im p lifie d sk e tc h o f ph e n o m e n a in vo lv e d in b io lo g ic a l ph o s ph a te re m ov a l in w a te r (C o m e a u e t a l., ) C a p tio n : m e ta b o lism in a n a er o b io sis m e ta b o lism in a er o b io sis

22 R a w w a te r F lo w Q DO C, P, N H 3 R e c irc u la tio n o f mi x e d liqu o r 2 x Q E x c re tio n o f P : + Q 1 A c in e tob a c te r, M o r a x e lla A n a e rob io s is z o n e M O C OH A e : DO C + O 2 C O 2 + H 2 O NO D O C N 2 + C O 2 M O C OH A n : d e n itr ific a tio n A cc u m u la tio n o f P : -Q 2 > > Q 1 N itr o s o m o n a s e t N itrob a c te r : N H 3 + O 2 NO H 2 O U p s tre a m a n o x ic z o n e A c tiv a te d s ludg e ta nk A ir P ho s pha te d s lu d g e r e c ir c u la tio n (Q to 2 x Q ) F ig u re 1 9 : S k e tc h o f a s tr u c tu re o f b io lo g ic a l r e m o v a l o f D O C, N a n d P in M WW T re a te d w a te r (Q ) S e ttlin g ta n k P ho s pha te d s lu d g e ex tra c tion

23 F ig u re s 20 to 2 5 : M a in fila m e n to u s b a c te r ia r e s p o n s ib le fo r b u lk in g in a c tiv a te d s lu d g e p r o ce sse s * s k e tc h * m o rp h o lo g y, G ra m s ta in, N e iss e r s ta in, s u lp hu r g ra nu le d e te rm in a tio n * c la ss ific a tion (B e r g ey s M a n ua l o f S y s te m a tic B a c te r io lo g y, J.G. H o lt e t N.R. K r ie g, ) a n d re la tio n s h ip w ith w a te r trea tm e n t

24 N o c a r d ia s p. : sh o rt a n d b ra n c h e d fila m e n t, n o n p a rtitio n e d,g +, N +, S - 50 µ m S e c tio n 2 6 : A c tino m y c e ta l S ta b le fo a m o n th e s u rfa ce o f th e a e ra te d ta nk ; e x ce ss o f g re a s e in M WW F ig u re 20 T h io th r ix sp : s tra ig h t o r n o t m u c h c u rv e d fila m e n t, n o n b ra n c h e d, w ith o u t sh e a th, p a rtitio n e d, s u lp h u r g ra nu le ( ), G -, N -, S µ m S e c tio n 2 3 : g lid in g b a c te r iu m, non pho to s y n th e tic a n d w ith o u t fru c tific a tio n ; o r d e r B e g g ia toa le s S e p tic M WW c o n ce n tra te d in su lp h u re d re du ce d c o m p o u n d s F ig u re 21

25 B e g g ia toa s p. : fle x ib le fila m e n t, m ob ile, p a rtitio n e d, s u lp hu r g ra n u le, G -, N -, S to 300 µ m S e c tio n 2 3 : g lid in g b a c te r iu m, non pho to s y n th e tic a n d w ith o u t fru c tific a tio n ; o r d e r B e g g ia toa le s O b s e rv e d in in su ff ic ie n tly a e r a te d a tta c h e d g ro w th F ig u re 22 H a lisc o m e no b a c te r : T h in a n d s tra ig h t fila m e n t, n o n p a rtitio n e d, sh ea th, G -, N -, S µ m s h e a th c y to p la s m ic m e m b ran e S e c tio n 2 2 : s h e a th e d b a c te r ia In s u ff ic ie n tly a e ra te d sludg e F ig u re 23

26 M ic r o th r ix pa rv ic e lla : th in fila m e n t, s inu o u s, e n ta ng le d, G +, N +, S to 500 µ m on e fila m e n t In s u ff ic ie n tly a e ra te d sludg e ; in su ff ic ie n t rec irc u la tio n flo w F ig u re 24 Spha e r o tilu s n a tan s : lo n g fila m e n t, q u ie t stra ig h t, p a rtitio n e d, sh e a th, fa lse ra mi fic a tio n s, g ra n u le s P H B ( ), G -, N -, S - 1 mm ce ll F a ls e ra m ific a tio n g ra n u le o f P H B s h e a th S e c tio n 22 : s h e a th e d b a c te ria D e fic ie n c y o f n itro g e n, p h o s p h o ru s o r o x y g e n T oo h ig h o r too lo w lo a d F ig u re 25

27 W a s h w a te r in le t S c ree n e d floo r T re a te d w a ter A tta c h e d g r o w th T h in g r a n u la r m e d iu m DO C + O 2 C O 2 + H 2 O M O C OH A e A ir p ro ce ss F lo w o f w a s h w a te r N itro so m ona s an d N itrob a c te r : C L A A e : n itr ific a tion N H 3 + O 2 NO H 2 O a e r o b ic z o n e p ro cé d é A n o x ic z o n e H e te r o tr oph ic d e n itrific a tio n DO C + NO 3 - N 2 + C O 2 M O C O H A n rec irc u la tio n o f n itra te s W a s h a ir R a w w a ter la v a g e W a s h w a te r ou tle t F ig u re 2 6 : S k e tc h o f a s tr u c tu re o f M W W tr e a tm e n t b y b io filtr a tio n : b io lo g ic a l r e m ov a l o f D O C a nd N (p r o ce ss B io s ty r, O T V )

28 R o ta tiv e s p rin k le r fo r ra w w a te r sp re a d in g F ilte r m e d iu m M O C OH A e : DO C + O 2 C O 2 + H 2 O and po ss ib le n itrific a tio n (M O C L A A e ) T re a te d w a te r R a w w a te r C h a n n e l fo r trea te d w a te r o u tle t F ig u re 27 : S k e tc h o f a tr ic k lin g filte r

29 R o ta tiv e b io d is c M O C OH A e : DO C + O 2 C O 2 + H 2 O L e v e l o f w a te r DO C a d s o rp tio n o n th e b io film A x is o f th e d is c C h a n n e l M WW F ig u re 2 8 : S k e tc h o f a b io d is c ; w a te r c irc u la te s in a p la n e p e rp e n d ic u la r to th e p la n e o f th is s k e tc h, a n d p a ra lle l to th e d ir ec tio n o f th e a x is

30 L ay e r o f w a te r : d ia to m ite s a nd c y a n ob a c te ria O x yg e n a te d s lu d g e : o x id iz in g s u lp h u r a e rob ic mi c ro - o rg a n is m s (B e gg ia to a, T h iob a c illu s, T h io th rix ) p h o too rg a n o tro ph ic : n o n su lp h u ro u s p u rp le b a c te ria (lo w [H 2 S ] ) R ho d o s p ir illu m an d R ho d op s e u d o m ona s (R hodo s p ir illu m, R hodop se udo m o na s ) A n o x ig e n ic p h o to s y n th e s is w ith s u lp h u r re d z o n e : C h r o m a tiu m ; a ss im ila tio n o f C O 2 in c a rbo n a te s g r e e n z o n e : C h lo r ob iu m L I G H T d iff u s io n o f H 2 S S lu d g e + N a 2 S O 4 + N a 2 C O 3 + ce llu lo se : d e g ra d a tio n o f c e llu lo se a n d fe rm e n ta tio n s b y C lo s tr id iu m ; a n a e rob ic s u lph a to re d u c tio n a n d fe rm e n ta tio n s (D e s u lfo v ib r io ) : u p w a rd d iff u s io n o f s u lph id e s F ig u re 29 : T h e W in og r a d s k y c o lu m n e x p e r im e n t

31 R a w w a te r S u n SS s e d im e n ta tio n C O D a lg a e O 2 b a c te ria C O 2, N O 3 -,... T re a te d w a te r to m a c r o ph y ta lag oo n : n itr a te s a n d ph o s ph a te s C H 4, N H 3, H 2 S... W a te rp roo f m e m b ra n e F e rm e n ta tio n s S e ttle d SS F ig u re 30a : S k e tc h o f a m ic r o ph y te s lagoo n in g I n le t o f w a te r fr o m m icr o ph y te s la g oo n C o llec tin g and r ev a lua tion o f p lan ts E n d o f C a n d N re m ov a l O 2 C O 2 T re a te d w a te r N itra te s a nd p h o s p h a te s a ss im ila tio n F ig u re 30 b : S k e tc h o f a m a c r o ph y te s lagoo n in g

32 P o ly m e rs (S lu dg e, IWW...) H y d ro ly s is a n d a nd a c idog e n e s is M is ce lla n e o u s o rg a n ic a c id s H 2 C O 2 H o m o ac e tic fe rm e n ta tio n a ce to g e n e s is O H P A In te rs p e c ific tra n sfe r o f d H 2 C H 3 C OO H H 2 C O 2 H y d rog e n o p h ilic m e th a nog e n e s is A c e to c la s tic m e th a nog e n e s is C H 4 C O 2 F ig u re 3 1 : T h e d iff e re n t w a y o f a n a e r o b ic d e g r a d a tio n o f o r ga n ic m a te r

33 ga s e x tr a c tion S tirr in g w ith ga s T re a te d w a ter DO C C H 4 I WW G a s re m o v a l S e ttlin g ta n k A n a e ro b ic re a c to r w ith s u s p e nd e d g ro w th S ludg e r ec ir c u la tio n S ludg e ex tr a c tio n F ig u re 3 2 : S k e tc h o f a s tr u c tu re o f I W W tre a tm e n t, w ith a n a e r o b ic d ig e s tio n s u s p e nd e d g r o w th

34 G a s A tta c h e d g ro w th F ilte r m e d iu m O rd e re d p a c k in g o r ra nd o m fill T re a te d w a te r I WW C OD C H 4 S lud g e e x tra c tio n A n a e ro b ic re a c to r F ig u re 33 a : S k e tc h o f a s tr u c tu re o f I W W a n a er o b ic d ig e s tio n a tt a c h e d g r o w th tre a tm e n t, w ith

35 b io g a s o u tle t tre a te d w a te r B io lite rec irc u la tio n F lu id isin g p u m p In le t ra w w a te r F ig u re 33 b : T h e A n a flu x S y s te m (D e g ré m o n t, F r a n ce )

36 R a w s lu d g e E n dog e n o u s r e s p ir a tio n : M O C OH A e : im p o r tan t o xy g e n d e m an d : B io m a ss and o r gan ic m a tte r + O 2 C O 2 + H 2 O + N H 3 + h e a tin g e n e r g y p a tho g e n ic m ic ro -o r gan is m s re m o v a l n itrific a tio n (C L A A e : N itr o s o m ona s e t N itr ob a c te r : C L A A e : n itr ific a tion N H 3 + O 2 N O H 2 O S lud g e a g e : 1 5 to 2 0 d S ta b le s lu d g e A I R F ig u re 3 4 : sk e tc h o f a s tr u c tu re o f a er o b ic s ta b iliz a tio n o f s lu d g e

37 g a z in le t fe e d in g th e b o ile r G a s m ix in g o r m ec han E x tr a c tio n o f b ioga ic a l a g ita tion s C OD C H 4 R a w s lu d g e S ta b le slu d g e B o ile r a n d h ea t e x c h a n g e r F ig u re 35 : S k e tc h o f a m o d e r a te loa d d ig e s to r

38 T h ic k e n e d s lu d g e in le t W a s te g a s b u rn e r G a s s tirring B e g in n in g o f m e th a n is a tio n H e a te d s ludg e rec irc u la tio n B o ile r a n d h ea t e x c h a n g e r F ig u re 36 : S k e tc h o f a h ig h loa d d ig e s to r E n d o f m e th a n is a tio n S ta b le slu d g e o u tle t

39 P a rtia lly d r ie d, fre sh, r a w s lud g e : o rg a n ic m a tte r (in s u ff ic ie n t C /N ) + w a te r ( 6 0 % ) + m in e ra l m a tte rs + p a th o g e n ic m ic r o -o rg a n is m s A dd itio n o f s tru c tu rin g ca rbo n a ce o u s c o m p o u n d (s a w du s t ) : * s ludg e a e ra tio n, p a rtia l d e w a te rin g * a d d itio n o f C M O C OH A e e nd o g e n o u s : b a c te r ia, m o u ld, m u sh r oo m C O 2 + H 2 O + in c re a se o f te m p er a tu r e (5 0 to 70 C ) + N H 3 + re s idu a l o rg a n ic m a tte r + m in e ra l m a tte r e v a p o ra tio n o f w a te r P a th o g e n ic mi c ro -o rg a n is m s re m ov a l C o m p o s t m a tu ra tio n fo r 2 to 3 m o n th s w ith re g u la r mi x in g : N itrific a tio n O x y d a tio n o f re s idu a l o rg a n ic ca rbo n e T h e fin a l s lud g e : is d ry (d r y n e ss = 6 0 to 7 0 %) is n o t p a th o g e n ic is a m a rk e ta b le o rg a n ic s o il im p rov e m e n t F ig u re 37 : S k e tc h o f s lud g e c o m p o s tin g

40 C U nd e s ir a b le c o m p o u n d O r ga n ic c a r b o n : B O D 5 A m m o n ia o r ga n ic n itr o g e n O r ig in in M WW A v er ag e c o n ce n tr a tio n in M WW O rg a n ic m a tte r 100 to 400 m g O 2 /l a m m o n ific a - -tio n o f u rea, p ro te in s p ro te in s, u rea N itr a te s A b s e n t in M WW P re s e n t in w a te r a fte r n itrific a tio n o f KN P h o s p h o r u s O rg a n ic m a tte r a n d w a sh ing po w d e rs KN = 30 to 10 0 m g /l E x a m p le o f d is c h a r g e s ta nd a r d T ox ic ity o r in c o n v e n ie n t 25 m g O 2 /l C o n s u m p tio n o f O 2 in th e m e d iu m NK + n itra te s = G L N = 0 10 m g /l c o n s u m p tio n o f O 2 to x ic fo r fa un a e u trop h ica tio n P h y s ic a l re m ov a l p re -tre a tm e n t b y c la rific a tio n : re m ov a l o f C, N a n d P lin k e d to SS 10 to 2 5 m g /l 1 m g /l p rec ip ita tio n w ith F e C l3 B io lo g ic a l p r o ce ss * s u s p e nd e d c u ltu re s A S o r AD (fo r a g ri fo o d IWW ) ** a tta c h e d g ro w th (D,B f,t f) * s u s p e nd e d c u ltu re s A S ** a tta c h e d g ro w th (D,B f,t f) * s u s p e nd e d c u ltu re s A S w ith up s tre a m a n o x ic z o n e ** a tta c h e d g ro w th B f A S w ith a n a e rob io s is z o n e I n v o lv e d m icr o - o r ga n is m b a c te ria, p ro to a n d m e ta z o a * flo c c u la ting * in b io film : fo o d c h a in N itro so m ona s a n d N itro ba c te r mi sce lla n e o u s : e n te rob a c te - -ria, P s e udo m ona s A e r o m ona s A c in e tob a c te r M o r a x e lla N u tr i- tio n a l ty p e R o le o f C in th e m e ta b o lism P r o d u c t o f re a c tio n ( C O H A S o u rce o f e lec tro n s a n d C C O 2 C L A A e S o u rce o f e lec tro n s N O 3 - C O H A n F in a l a cce p to r o f e lec tro n s N 2 C O H A e In tra ce llu la r a cc u m u la tio n o f P in s ludg e ) F ig u re 3 8 : B io lo g ic a l tre a tm e n t o f M WW C a p tio n : A S (a c tiv a te d s lu d g e ) ; AD (a n a e r o b ic d ig e stio n ) ; D (d isc ) ; B f (b io filte r ) ; T f (tr ic k lin g filter ) C o nd itio n fo r th e tre a tm e n t * o x y g e n a tio n * lo w lo a d * o x y g e n a tio n * lo w lo a d *h ig h s ludg e a g e * e ff ic ie n t n itrific a tio n * a n o x ia * p re s e n ce o f o rg a n ic m a tte r * n e ith e r O 2 n o r NO 3 - * a e rob ic s ludg e tre a tm e n t

41