used for andenhanceddewatering. disinfection involvemechanisms employing additivesoptimise mainly to andare andcontrolreactions, desired Chemical activityofmicroorganisms. viathe andpathogens constituents, of organic andtransformation removal berobust. to allow considered Biologicalmechanisms the generally most and are widely employed methodologies, FS treatment the These are in current mechanisms andvolume reduction. drying ofFS.Physical treatment includedewatering, mechanisms used for the physical, mechanisms biological,andchemical the sections,presenting three isdividedinto This chapter treatment wastewater specifi textbook anengineering to on refers reader the that itisrecommended mechanisms, topic. this c to information background detailed more For operation and technologies. design treatment the FS improve of to order in overcome is knowledge of lack this that important is It years. over the observations and has been acquired via empirical (FSM) FS management islimited ofphysical, in mechanisms biological andchemical andviscosity.content understanding Thecurrent sizeanddensity, load,particle dissolved organic pH,water , temperature, include stabilisation, consider to sludge (Spellman,1997;mechanisms ofthe properties Kopp 2001). andDichtl, Important andhave effi impact adirect from wastewater, on the greatly differ FS characteristics ciency oftreatment cannot bedirectly technologies transferred. these that remember to butitisimportant treatment, sludge andwastewater rely. developed for wastewater Many basedonthose are technologies FStreatment discussedinsubsequent chapters technologies treatment the onwhich based,andhighlightsthose are processes (FS)treatment sludge faecal onwhich mechanisms ofthe anoverview presents This chapter 3.1 INTRODUCTION • Learning Objectives • Understand the mechanisms for key parameters that can be controlled to increase treatment treatment increase to controlled be can that parameters key for mechanisms the Understand • of needs maintenance and operation the affect mechanisms how into insight basic a Obtain • mechanisms treatment biological and chemical physical, of combinations how Understand • Know the difference between physical, mechanisms. andbiologicaltreatment chemical difference Know the efficiency andmeet objectives. treatment technologies. treatment treatment. sludge for responsible faecal are Magalie Bassan, Pierre-Henri Dodane andLindaMagalie Bassan, Pierre-Henri Strande Treatment Mechanisms Treatment Chapter 3 45

Technology Technology the weight of the solidsfrom above, liquid. removing more weight ofthe the blanket sludge is‘squeezed’ by whenthe bottom ofasettling tank ‘blanket’. Compression atthe occurs asa settle outtogether particles streams,the where waste inhighly concentrated settling occurs Van through der Waals held together are settlingforce, in increased resulting velocities. that Hindered mass and settling velocity. for their smaller particles increasing and merge, This is important together join whenparticles Flocculentsettling occurs particles. other with reacting individually without settle out streams whenparticles waste inlower settling concentration occurs particle Discrete flThe four particle, typesofsettling includediscrete mechanisms andcompression.occulent, hindered, chambers. 6) andgrit and flocculation. These are (Chapter basic used fundamentals design in of the tanks settling-thickening suspended solidsconcentration, basedonsizeofparticles, settle outunderquiescent conditionsatrates water heavier are than that Particles andunboundwater. ofsuspendedparticles separation the achieve most commonly employed inFSM.Itcan isprobably the Gravity ofliquid –solidseparation method separation Gravity 3.2.1 orevaporation. pressure useofcentrifugation, orthe additionofchemicals the itrequires water; free isphysically diffi more solids,itismuch liquid. boundto Whenwater the releasing removecult to than lysingofcells,thus inthe result andisonly removed by that mechanisms treatment , within iscontained water andadhesion.Intracellular by adsorption solidsandmicroorganisms to isbound ascolloidalwater) to (alsoreferred water forces. Surface capillary solidsthrough bound to spaces,but isinpore water) ascapillary to (alsoreferred water Interstitial ofbound water. forms andintracellular 3.1, surface, forces. Asshown includesinterstitial, inFigure by boundwater capillary assettling such orfi technologies phase by dewatering Itisnot adsorbed,bound,orinflltration. uenced solid from the Itcanbeseparated sludge. inuntreated ofwater majority the usually represents water) is diffimuch more bound water of the as to bulk (also cult referred (Kopp and Dichtl, 2001). water Free easily isfairly removed, whileremoval water free becausethe mechanisms treatment understanding in differentiation This isan important Water orbound forms. infree inFS can beavailable fi force andpressure. evapotranspiration, centrifugal attraction, charge gravity, surface ltration, isbasedonphysical processes asevaporation, such composting, orcombustion asafuel.Dewatering for as applications such recovery resource to prior is also necessary impacts.negative Dewatering environment hassignifi the to water polluted this anddischarging transport, and expensive to cant comprised mainly is FS dewatering. is technology. typeofonsite Water isdependentonthe ofwhich FSM isheavy proportion the of water, in mechanisms treatment important most the of One PHYSICAL MECHANISMS 3.2 iue31 Water forms in asludge floc (adapted from Kopp and Dichtl, 2001). Figure 3.1 46 Interstitial water Free water Surface water Intracellular water g = Gravitational constant (9.81 m/s constant g =Gravitational d Equation 3.3:F law asshown inEquation 3.3: Stokes’ the by represented be flcan (non-turbulent force number drag the particles, spherical and ows) low Reynolds For of gravity. that to direction opposite force is also in the and turbulent). The drag coeffidrag fl numberandthe Reynolds isafunctionofthe cient which ow (laminar, regime transitional, fl velocity anddiameter, the particle force isdependent onthe The drag uid densityandviscosity, anda (9.81 m/s constant g =Gravitational for settling, where the terms for F terms for settling, the where superfi is the design parameter and the Equation 3.4 times is length). called cial Stokes’ Lawarea (width velocity. The needed of length tank forthe to particle this settle can be calculated based on velocity,this settling isatitsterminal particle forces equals0,the to gravity,anddrag buoyancy sumofthe When the d F Where: ρ F Where: μ =Water viscosity (N Where: V ρ V d Equation 3.2:F liquid. densityofthe sign inEquation 3.2),anditisdependentonthe negative by the ofgravity, (represented that to direction opposite isinthe The forcebuoyancy dueto layer as there istypically asignifilayer asthere cant accumulation(Figure3.2). ‘scum’. In design the and of ponds stabilisation settlingfor tanks FS, it to is address scum important the is suffi as to liquid isreferred ofthe flcient to surface onthe forms Thelayer that surface. the to oat them have this water, asimilar densityto andifthey particles, to Airbubblescan attach oils,andgrease. fats, cells, whensuspendedsolidshave for occurs asimilarorlower example algal water, densityto Flotation Equation 3.4: F Equation 3.1: inEquation 3.1. aspresented canbecalculated Theforcegravity dueto particle. volume ofthe the fl and the particle densities of the force is dependent on the The gravity resistance). frictional uid, and mainforces infl three are There force (or gravity,anddrag buoyancy settling ofaparticle; uencing the b g L p p p p p p = Force due to gravity (N) gravity dueto =Force = Force due to buoyancy (N) buoyancy dueto =Force =Densityofliquid (kg/m = Particle density(kg/m =Particle = Diameter of the particle (m) particle ofthe =Diameter (m) particle ofthe =Diameter = Diameter of the particle (m) particle ofthe =Diameter = Particle volume (m =Particle volume (m =Particle g d b v = =-3πμd = particle mass = particle = liquid mass . (ρ

s/m 3 3 ) ) p - ρl)gd 3 18 p ) 2 3 ) ) μ 2 p . g

+F

g =-ρ . g=ρ 2 2 ) ) b +F L p

. .

d

V V = 0 are substituted: substituted: =0are p p

. .

g =-ρ g =ρ p L (1/6 πd (1/6πd p p 3 3 )g )g 47

Technology Technology the head loss of the liquid, or the energy each unitvolume each fl energy needsto liquid, orthe headlossofthe the fi the ow through lter. fidivided by the fi of the The depth area. surface lter time, and hydraulic retention the determines lter fiby the fi the volume passing through asthe and reported iscalculated lter. The rate inone hour,lter fl to resistance bedisdependent onthe the through (by gravity) percolates that fraction ow exerted 7and8).Thefl bottom (Chapters atthe gravel to top size media,from sand atthe liquid ofthe ow rate layers of increasing usually beds are designed with potential for clogging. FS drying of loaded FS and the solidsconcentration the mustand removes bebalanced with solids.Theneedfor more solidsremoval fi solids,whereas ofmore passage liquid fl the to resistance frictional ner mediaprovides agreater ow sizesoffiVariable the spaces andallows pore hasmore media(e.g.gravel) mediacanbeused.Coarse lter removed not are by aseffectively fi assmallerparticles performance affect ltration. can sizedistribution andparticle performance, overall andthe surface atthe solidsretained impact the infl inthe higher suspendedsolidsconcentrations fiuent canincrease clogging,fllter can oc strength infl typeoffiuent, the fi media,and the ltration (Metcalf andEddy, loadingrate lter example, 2003).For impact onslow fi greatest have the that The parameters effiltration ofthe characteristics the ciency are rates. faster than andmaintenance lessoperations requires which solids. In fifrom the beds, slow fi drying lter fi with is occurring ltration of 0.1-0.4 m/h, rates ltration fithe fi the through liquid percolates bed,whilethe lter orevaporates inadrain, bedandiscollected lter beds.Theseprocesses usefi unplanted drying are andplanted of surface solidsonthe trap mediato lter (biosolids)processing. sludge However,most commontypes andtreated inFSMthe wastewater water, appliedto are orpressurised) driven andtypes(e.g.slow, gravity rapid, granular) media (e.g.membrane, fi inFSM.Several isalsoacommonly for appliedmechanism liquid –solidsseparation Filtration ltration 3.2.2 Filtration tank at Niayes Settling sludge faecal treatment plantinDakar, (photo: Senegal Linda Strande). Figure 3.2 48 Equation 3.5: Wood, 1974): fl to resistance The laboratory. fi‘clean’ a by exerted ow and (Huisman 3.5 Equationby given be can lter fi ofthe laminarconditions.Theresistance ensure enough to slow inthe mediaisbest determined be ltering to fl considered fithe is sand as ow slow ltration, of modeling the in used be can law Darcy’s modelshaveDiverse beendevelopedbasedonfi behaviors. observed explain to mechanisms ltration above four removed mechanisms. by oneofthe then are which particles larger form to of particles particles are removed from the liquid flow when they stick to the fi lter media. Flocculation is the joining liquid fl ofthe path ofthe mediaasaresult with contact comeinto particles ow. when occurs Adhesion settling. Interception is when media of is gravity a result the onto Sedimentation pass through. able to sizeandnot pore the than larger are basedonsizebecausethey exclusion ofparticles isthe Straining processes cannot be individually quantifi calculations. on empirical beds relies design of drying ed, the for responsible fi are The mainphysical that mechanisms 3.3.Asthese shown are inFigure ltration to ensure that fi that ensure to donot infi result ne soilparticles clogging. lter the operating and building fidesigning, whenbuildingafiwhen sandandgravel usewashed to 7and8).Itisalsoimportant (Chapters lter taken bed, lter be to needs care occurring, from this prevent To fi incloggingofthe Thiscanresult head lossesincrease. offi decrease andarapid lter effiltration ciency. fi ofthe surface for liquidspassthe to resistance the increases lter, fl inreduced andresult as ow rates fiof ner slow sandfiamounts With particles. fi of the greater surface on the trapped solids are most ofthe ltration, of retention lter. This the fi with the lter effiof increased ciency in results ‘ripening’, as known phenomena, This media. the biofion biological develops a lm of growth fi the the and lter, fi ofthe operation During in trapped are sizeswillbecomesmallerasparticles pore effective lter, the coeffik =Permeability cient (m/s). bed(m) ofthe h =Thickness iue33 Schematic presentation ofthemechanisms affecting flow infi lter media(modifi ed from Metcalf and Figure 3.3 v cleanfi ofthe H =Resistance drop (m) bedorpressure lter Where: f = Filtration rate per unit area of the bed(m/s) ofthe perunitarea rate =Filtration collude withmedia Large particle Str aining Eddy, 2003). H = on media Sedimentation v k f

. h Interception leads tocollusion Flow streamline Adhesion to themedia Attachment offlocs 12 Flocculate another mechanism attach tomediathrough P articles flocculateand 12 49

Technology Technology E Where: Equation 3.6:E air(Equation 3.6): ofthe pressure vapor illustrated by Dalton’s law of partial pressure, of rate depends the evaporation on wind velocity and the air. As dry air with of saturated replacement the as it increases of evaporation, rate on the has an effect speed also Wind for heat requirement evaporation. the canincreasing be stored, that energy more the massofanobject, total the bed.Thelarger drying ofthe area andtotal depth are parameters Important (MusyandHigy, insludge) infl water versus 2004). water standing (e.g.free rate evaporation uence the canalso isoccurring evaporation fromthe where Thesurface especially ofairare important. content isstrongly inflconvection). Thus,evaporation heat andmoisture available uenced byandthe climate, lossesdueto occurisprovided to (with by solarenergy for required evaporation The energy airisnot saturated. the means that demand,which environment have needsto surrounding anevaporative occur, to mechanisms the both For evapotranspiration. bedsthrough drying planted andwith evaporation, through also occurring two fi Inadditionto mechanisms. combinationofthese is the bedsis indrying dewatering ltration, processes. Evapotranspiration metabolic oftheir airasapart the to vapour water plantsrelease which process by isthe airasavapour, andtranspiration the into isreleased whenwater occurs Evaporation Evaporation andevapotranspiration3.2.3 fi the within al.,2009). andBOD et occurring ofnutrients biological removal (Panuvatvanich lter availability. ofoxygen,in presence Thiscanalso result andnutrient carbonsources depending onthe fi the happensthroughout Biological growth surface, nearthe intense bemore lter, to buttends infl result processes that Chemical processes includeattraction fiocculation oradhesionto surfaces. lter fi the physicalIn additionto and biologicalprocesses chemical alsooccurwithin mechanisms, lter. bedsat Niayes Drying sludge faecal treatment plant, Dakar, (photo: Senegal Linda Strande). Figure 3.4 50 e e’ windvelocity ofthe constant f(u) =Proportionality s a a = Effective vapor pressure (mmofmercury) pressure vapor =Effective = Contribution of mass transfer to evaporation (mm/day) evaporation to ofmass transfer =Contribution = Vapor pressure of water at saturation at the temperature of the surface (mmof mercury) surface ofthe temperature atthe =Vapor atsaturation ofwater pressure a =f(u) . (e’ a -e s ) G =Soilheatflux density(MJ/m γ R (kPa/°C) curve pressure vapor saturation ∆ =Slopeofthe in(mm/day) evapotranspiration PET =Reference Where: Equation 3.8: typesofplants. several locations,andbetween year, indifferent ofthe periods atdifferent ofevapotranspiration comparison al., (Allenet 1998; rate evapotranspiration Uggetti potential the inEquationevaluate 3.7)isusedto equation (aspresented Penman from the derived equation, involves andadjustments. ThePenman-Monteith extrapolation control experiments for adefi determined experimentally are that on values the andlocation.Therefore, ned context relies therefore Calculatingevapotranspiration beconsidered. typesneedsto reference standard to typeandcomparison vegetation asthe evaporation measuring complex Thisismore sites. than reference invegetated lossismeasured water To transpiration, measure Maximal Evapotranspiration. the smallerthan isalways ofplants.Thisvalue state relative humidity, rate, andgrowth evaporation recorded utilisesthe conditions.Actual Evapotranspiration phase,assumingoptimal growing growth for individualplantspeciesandfor each canbedetermined phase.MaximalEvapotranspiration growth inanintensive- andplantsare isdenseplantcoverage, there isavailable, water adequate assuming that evapotranspiration lossthrough water theoretical accountsfor the Potential Evapotranspiration (MusyandHigy2004). ofevapotranspiration rates for measuring accepted methods afew are There allow to maximumbiomass productionbe considered ofplants. needto data loadandrainfall sludge beds,the drying planted occurwith to optimal evapotranspiration 2011). For Tsihrintzis, and (Stefanakis evaporation on than infl greater evapotranspiration a on uence have variations temperature that Ithasalsobeenobserved alone(MusyandHigy,evaporation 2004). of rate the than greater isalways ofevapotranspiration ofleaves. Therate surface onthe stoma, pores by released the plant,andthen ofthe system circulation internal the through is transported water transpiration, 2011). Tsihrintzis, During and (Stefanakis zone root the in availability water and color, phases,plantdensity, leafshapeand asplantspecies,growth such dependent onadditionalfactors infl are oftranspiration rates evaporation, As with uenced by also heat,moisture, andwind,butare heatofvaporisation λ =Latent E γ (kPa/°C) curve pressure vapor saturation ∆ =Slopeofthe in(mm) E =Evaporation Where: Equation 3.7: al.,1998). (Allenet requirements’ –Guidelinesfor computing crop water as‘Crop andindocumentssuch evapotranspiration org), (www.fao. Nations United the of (FAO) Organisation Agriculture and Food the as such websites on cantypically befound Thistypeofinformation basedonlocalclimaticdata. evaporation calculate to factors empirical incorporates and law Dalton’s utilises 3.7 Equation in shown formula Penman The = Psychrometric constant (kPa/°C), (kPa/°C), constant =Psychrometric = Psychrometric constant (kPa/°C), (kPa/°C), constant =Psychrometric c n = Evaporation measured on a Colorado basin(mm) onaColorado measured =Evaporation = Net radiation at the crop surface (MJ/m crop surface atthe =Net radiation PET = E = + +2 0.408 γ γ . E 2 c .. /day) - () γ ( R γ γ (2-λ) +2 + = 0.00163 = 0.00163 n γ -G + . . (1+C E γ ) 2 2 /day) γ T+2 d .

u . . C et al.,2012).et Thisequation (Equation the 3.8)allows P/

, where P = Atmospheric pressure P=Atmospheric P/λ, where n 2 73 γ ) , where P = Atmospheric pressure P=Atmospheric , where u 2 . (e s -e a ) 51

Technology Technology

e u at2mheight(°C) T =Meandaily airtemperature from the center of a cylinder to its surface can be calculated by canbecalculated Equation 3.9(Spellman,1997): ofacylinder itssurface center to from the movement the force driving its initialmovement. toward Thecentrifugal anya force against obstacle inmovement itexerts itsdirection, isforcedchange to whenaparticle that fact This processonthe relies separately.collected then are Theliquid andsolidfractions andconcentrated. pressed are they where walls, centrifuge at the process. Solidssettle out sedimentation the forces accelerate centrifugal atahighspeed,and the rotates while it centrifuge Sludge is placed inside the of bound water. employed removal partial for FS for the butcanalsobe sludge, ofwastewater ismainly usedfor liquid – solid separation Centrifugation 3.2.4 Centrifugation C Plantedbedsinthegarden ofaschool, drying Bangkok, Thailand. Thelarge leafs contribute to the Figure 3.5 52 C e a s 2 d n = Vapor pressure at saturation at the temperature of the surface (kPa) surface ofthe temperature = Vapor atthe atsaturation pressure = Effective vapor pressure (kPa) pressure vapor = Effective =Daily windspeedat2mheight(m/s) =Coeffi (mm) vegetation and0.38for tall vegetation, for short 0.34 cient: =Coeffi and1600 vegetation, vegetation 900for short for tall cient: evapo-transpiration anddewatering ofthesludge (photo: Linda Strande). fl settleability, scrollability andthe the plantsare treatment the (Kopp 2001). andDichtl, oc strength were identifi that characteristics important three from sludge wastewater with beimportant ed to inflThe parameters effiuencing the not are completely but understood, centrifugation ciency ofthe V =Volume (m) particle ofthe ρ (m) particle the to ofrotation center from the r =Radius persecond) W =Angularvelocity (radian force (N) Fc =Centrifugal Where: in wastewater sludge is reported to be1.95 to (KimandParker, kJ/kg/°C 2008). isreported sludge in wastewater by water 1°C. were values No found literature forheat capacity the of FS, heat but capacity the of solids of 1kg of temperature the raise 4.18 is 25°C to at needed are 4kJ water of that means which kJ/kg/°C, specifi the example, For 1°C. by capacity mass heat unit c a of temperature the raise to required energy specifi dependsonthe The amountofheatrequired amountof isthe FS,which c heatcapacityofthe (Chapter 5). systems drying ininfrared andradiation systems, drying conductioninindirect employed systems, drying indirect involves processes. Convectiondrying is convection, ora combinationofthese conduction,radiation, Heat moisture content. andthe temperature sludge, the of the physical characteristics depends on the that atarate and evaporated surface the to moisture isalsobeingtransferred internal be transferred, humidity,temperature, fl As heat is continuing to sludge surface. exposed ow and the and pressure, ambientair dependsonthe that atarate surface, sludge atthe water offree evaporation the allows which heatsource, from anexternal transferred energy through isincreased sludge ofthe temperature The ofvapour. form islost inthe weight andvolume aswater both reduction, achieves Heat drying andpilot studies. from manufacturers canbeobtained information andfurther shouldbetransferable, technology for FS,butthis processing sludge than for wastewater is appliedmore passive, more orconventionalCurrently, other heatdrying methods. with achieved (biosolids)beyond sludge whatcanbe wastewater anddewater evaporate isusedto Heat drying Heat drying 3.2.5 retained. quantity and typeofsolidwastes dependsonthe aheadlossthat create fl ofthe strength the dueto bars the beingpulledthrough wastes coarse 1976).ow (Mara, Thebars Thefl 0.3m/sfor wastewater). than velocity (greater ow shouldalsonot exceed 1m/sinorderavoid to fl shouldbeavoided.which the Therefore, self-cleansing ow ataminimum,the velocity shouldreach, it, leading upto channel solidsdeposition inthe ofsolids,butinvolves removal an increased agreater flThe velocity ofthe infl bars the ow ofFSthrough Alow velocity allows performance. screen uencesthe trapped. solidsare larger while the canfl liquid andsmallsolid particles the set that are such bars between the 3.6). Thedistance ow through incoming fl the or inclined position against solids (Figure coarse retains that ow make a physical barrier in a vertical endproducts. of treatment installed Bar screens value and enhancing the and pump failures, clogging preventing FS,thereby solidobjectsfrom the andlarge removeimperative to municipalwaste infl physical atthe inFSM.Barscreens mechanism important isanother Screening are uent ofaFSTP 3.2.6 Screening liquid (kg/m ρ =Densityofthe Equation 3.9:F s = Density of the particle (kg/m particle =Densityofthe c =Wr(ρ s -ρ)V 3 ) 3 ) 53

Technology Technology sludge sludge consists of particles like cellulose, lignin, inorganic matter, and cellular matter of microorganisms uponscientifiagreed Stabilised c defi biodegradation. further to resistance to refers nition, butingeneral exact an have not does matter organic ‘Stabilised’ (Vesilind,2001). manipulation and storage easy for andallow odors, reduce characteristics, andpredictable oxygen demand,produce stable the reduce to inorder This is important organics. less degradable leaving stable, behind more material, degradable fi to prior stabilised of putrifi involves degradation nal enduse or disposal. Stabilisation the able, readily butusually source, be needsto dependingonthe inFSvaries matter organic The biodegradable environment. the canaffect byproducts that andother gases alsorelease They binding upnutrients. matter, and andreleasing oforganic by system, modifying forms the dynamically are altering they microbes grow, Asthe usually rely systems oncomplexTreatment populationsofmicroorganisms. outcomes. desired optimise processes,incontrolled andemployssituationsto the them occurring innaturally ofmicroorganisms rate andgrowth metabolism the harnesses Biological treatment following section. covered inthe are ofinactivation inChapter 2,whilemechanisms presented are ofconcern reduction. ofpathogen mechanisms inunderstanding Biologyisalsoimportant andnutrients. matter organic of transformation objectives oftreatment through achievement In FSM,biologyisessentialinthe BIOLOGICAL MECHANISMS 3.3 Barscreen at Niayes sludge faecal treatment plant, Dakar, (photo: Senegal Linda Strande). Figure 3.6 54 VSS magnesium,iron andcalcium. sulfur, potassium, includenitrogen, phosphorus, growth for orcarbondioxide. matter Essentialnutrients from organic cellscanbeobtained ofnew synthesis usedfor Thecarbonsource the andchemolithotrophs). (i.e.chemoorganotrophs orinorganic organic canbeeither forms chemical the (i.e.phototrophs, and chemotroph forms or chemical ), solarenergy (e.g.aerobic canbeprovided oranoxic). andelectronsource, Energy receptors through carbon source, includingenergy properties, metabolic basedontheir together grouped are 3.7, inFigure Asillustrated andcarbonsources. needenergy occur, to microorganisms growth For 3.3.1 Metabolism iue37 Nomenclature ofmicroorganisms requirements andcarbon based ontheirenergy (fiFigure3.7 gure: Linda Strande). VSS ofdegradation ρ =Percentage Where: Equation 3.10: ρ ρ=1(Kopp 2001). andDichtl, FS)ρ=0;whenfully andstabilised, digested FS (unstabilised ‘fresh’or ‘raw’ For treatment. FS during occurred has that degradation of level the assess to used be can matter. Equation 3.10 organic becomposed to considered are ofreadily degradable asthey stabilisation, Volatilecompounds proteins, andsugars. ascarbohydrates, such for usedasameasure solidsare easily degradable contains sludge unstabilised whereas organics, consumedreadily degradable that e- acceptor absence ofterminal NAD isregenerativee-acceptor substrate levelphosphorylation 0 1 =Volatile SuspendedSolids(g/L)attime0 =Volatile SuspendedSolids(g/L)attime1 (Heterotrophs) Chemoorganotrophs energystoragemolecules - oxidationtochargeup Energy source organic Chemotrophs

VSS O chemical 2 = aerobic = e- donor =(1-(VSS source e- acceptor terminal energy source proton motiveforce oxidative phosphorylation R espiration mineral e.g. Fe mineral becomesoxidised litho =mineral Chemolithotrophs

Other acceptor 1 = anaerobi /VSS P but couldbephotoheterotrophs most areautotroph hototrophs 2 +, S sun

c 0 )) it todriveanabolicreactions energy frome-donorandstores Generation of 2 , FeS .

100 2 A TP harnesess chemolithoheterotroph but couldbe organotroph typically chemo- Heterotrophic Organic C Carbon nutrientsource - buildcellularcarbon Autotrophic CO to organicmatter rubisco andconverted 2 CO grabbed byenzyme 2 55

Technology Technology 3.3.4 Aerobic treatment 3.3.4 CO from carbon and sun, the from energy molecules(e.g.incomposting). photoautotrophic, are getting their Algae organic recalcitrant of more stabilisation inthe important are ofenvironments. Fungi aerobic variety oranaerobic, andlive inalarge can be of , yeasts, comprised and mushrooms. chemoorganotrophs, They are of organisms, group alarge are Fungi predation. through pathogens ponds,andcanreduce andmaturation stabilisation frequently are predators of Protozoa bacteria. lack and chlorophyll and cell walls. They bacteria, also play an role important in than waste larger and motile often are They organisms. eukaryotic unicellular, are Protozoa risk. pathogenic determine helminthes and protozoa pathogenic while algae, and fungi protozoa, are mechanisms treatment for importance greatest of the FSM, In nuclei. bound The complex and cells enclosed membranes, contain haveof within structures eukaryotes a membrane or saltcontent). environments environmental chemotrophic, inextreme (e.g.hightemperature andmany grow archea history. all are They evolutionary intheir from bacteria differ orcocci(sphere). (spirals), spirilla 0.5-1 are Bacteria nucleus. a in enclosed not is DNA Prokaryotes their and eukaryotic. eukaryotes, than complex or less structurally prokaryotic celled, single are either archaea, and is bacteria of that consist structure cellular a have organisms living All Types3.3.3 ofmicroorganisms and 45-80°C) temperature (optimal thermophilic at 80°C orgreater). (optimal temperature hyperthermophilic 20-45°C), temperature (optimal mesophilic lower), or 15°C at temperature (optimal psychrophilic namely: range, temperature optimal their on canbedefi which four are typesoforganisms 3.8,there proteins. Asshown inFigure ned depending of denaturation dueto grow cannolonger above microorganisms which a maximumtemperature, and possiblerates; greatest happenattheir enzymaticreactions where range, an optimum temperature defi hasaminimumtemperature, cannot grow; organism pointbelow the which ned asthe Each for organism. each range agiven 10˚C growth within doubles for every intemperature increase Biologicalactivityoften isalsoheavily ontemperature. reliant ofmicroorganisms rate The growth 3.3.2 Temperature 56 and fi lters trickling reactors, batch sequencing sludge, activated include treatment wastewater in aerobicprocesses treatment inanaerobic conditions.Typical survive alsoable to are meaning they oxygen grow, to orfacultative purely aerobic requiring canbeeither Microorganisms respiration. rely onoxygen for ofoxygen, their presence andaerobic organisms Aerobic environments the to refer risk. pathogen asa aconcern primarily are InFSM,they a host. typically are They not livingorganisms. considered without not and are replicate able to protein plants, infect animals, and bacteria, able to capsid. They are ina orDNA andconsist ofRNA ofacore (20-300nanometers), bacteria smallerthan are Viruses ponds. andmaturation stabilisation role inwaste produce oxygen. play They animportant Figure 3.8 Partition ofthedifferent Partition oforganisms based ontheiroptimum types temperature. Figure 3.8 -20 0 20 40 2 T . Algae usechlorophyll plants,and to . Algae inasimilarfashion emp (˚C) 60 m in size, and have the shapeofbacilli(rods), μm insize,andhave the 80 100 120 140 60%, then it can impede microbial growth by anaerobic creating conditions. itcanimpede microbial growth 60%, then than is greater moisture content the pile. If the throughout nutrients occur, transport and to to for biologicalgrowth The optimal is40-60%by moisture content weight. Moisture isnecessary andnot matter bio-available. nitrogen is‘locked up’inorganic the 30,then than greater C:Nis orammoniavolatilisation. leaching Ifthe nitrate dueto willbelost following mineralisation that system willbeexcess nitrogen inthe 20there C:Nislower than Ifthe amino acids,enzymesandDNA. of nitrogen for synthesis with extraction, andenergy be abalanceofenoughcarbonfor cellsynthesis needsto There growth. their microbes utilisecarbonandnitrogen during that ratio 30, basedonthe andoxygen(C:N), moisture content, supply. optimal C:Nisbetween 20and observed Theempirically nitrogen massratio carbonto optimisation ofthe The composting the process iscontrolled through ascelluloseandlignin. moleculessuch organic recalcitrant more degrading phaseactinomycetes further this andfungiare During lowers. temperature and the down, activityslows bacterial depleted, are substrates readily degradable last of the asthe being reached is phase, stabilisation third Inthe high temperatures. ofthe asa result plant seeds (e.g. weeds) occurs of andinactivation reduction phase pathogen this matter. During organic decomposing the further active, become bacteria thermophilic and achieved are 50-75°C of temperatures thermophilic phase, second heat can atescape. which In the rate the than is faster which reactions), catabolic exothermic to (due ofgrowth rate rapid the dueto isalsoincreasing temperature the period, this protein). During compounds starch, (e.g.sugar, whileconsumingreadily degradable rapidly growing are bacteria fi the phaseprocess. During athree goesthrough system composting, the In thermophilic phase, rst compounds. ofnew microbial synthesis andthe andimmobilisationofnutrients, release the compounds, oxidation oforganic processthe are this govern that mechanisms decomposed. Important of added plant haveand animal residues major portions the after remaining matter soil organic of the defifraction is Humus stable amendment. soil the a as as ned used be can that matter humus-like rich, the same organisms that naturally organic matter degrade in the soil. The resulting endproduct is a dark, by occurs controlled matter Composting process by biologicaldecomposition which isthe oforganic 3.3.5 Composting Where C Where on aeration or mixing, which can be energy intensive. canbeenergy ormixing,which on aeration typically rely aerobic, remain they processes to low For solubilityofoxygen inwater. oxygen, andthe available depletes low microbial rapidly activitywhich dueto The dissolved oxygen inFSisvery content Organic matter +O matter Organic Equation 3.11: synthesised: cellsare and new respiration. As shown in Equation 3.11 during oxidation organic matter is consumed, CO consumed, is matter organic oxidation 3.11during Equation in shown As respiration. and endogenous growth, rapid during phases include oxidation and synthesis Aerobic growth bedsand composting. oxygen includingFSdrying ispresent, ponds. Aerobic processes occur in any or maturation solid or liquid process treatment where facultative Equation C 3.12: Equation 3.12: Thisisshown reaction. in metabolic maintain to consumecellularcontent and microorganisms isdepleted, matter organic readily degradable where period the to corresponds respiration Endogenous 5 H 7 NO 2 are the newly synthesised cells. newly synthesised the are 5 H 7 NO 2 +5O 2 g5CO 2 + nutrients gCO +nutrients 2 +2H 2 O +NH 2 +H 3 + energy +energy 2 O +C 5 H 7 NO 2 + other products +other 2 released, released, 57

Technology Technology Equation 4H 3.13: Equation 3.15 al. , 2003): et (Madigan Equation3.13in presented processesare Methanogenic temperatures. to (49-57°C) thermophilic and use the of hydrogen and carbon dioxide. occurs Methanogenesis more readily at mesophilic (30- 38°C) through produces methane group andcarbondioxide, whileanother methane into splitacetate archea of onegroup methanogenesis, methanogen 3.7).During (Figure aschemoorganotrophs Therefore, canbecharacterised archea accepters. and donors electron both as used are molecules Organic ). ammonia, heavy metals, andsulfiammonia, heavy metals, des. ofoxygen, presence free by alsostrongly inhibited the are Methanogens convenient andusefulmethod. most beingthe pHmonitoring with occurring, are andmonitoring operation consistent that ensure to important is it relationship, microbial balanced carefully this of Because ‘sour’. going digester the as to itisreferred activity. occurs, methanogenic Whenthis ofthe disruption lowered pH,andafurther reactor, ina resulting acidsproduced by volatile willbuildupinthe acidogens fatty the down, then process slows process. Ifthis inthe limitingstep isthe ofmethanogens rate slow growth Hence, the acidogens. for the pressure hydrogen an optimal partial produceduse the by acidogens, maintaining have asyntrophicThemethanogens relationship. microorganisms Acidogenic andmethanogenic (e.g.H substrates methogenic acidsto andfatty sugars, aminoacids, degrade further microorganisms acidogenic (oracidogenesis) fermentation During acids,andmonosaccharides. aminoacids,fatty into converted are proteins, lipids,andpolysaccharides sametime, At the bioavailable. andbecomemore compounds complex degraded and more are organic matter particulate which Hydolysisisanenzymaticprocess through acetogenesis andmethanogenesis. acidogenesis, by hydrolysis, fermentation, isacomplex process characterised anaerobic digestion. (i.e.microbial lesssludge biomass)isproduced during of anaerobic metabolisms, (Arthur (30-45%) dioxide carbon and 75%) production of that can be used for energy generation. Biogas is a mixture of mainly methane (55- can provideof sludge. Anaerobic a benefi digesters FS, as in it the also results of stabilising cial method can also be employedAnaerobic fermentation and settlingponds, septictreatment fortanks. the tanks, stabilisation waste oxygen where for hasbeendepleted, FSM systems example anaerobic andfacultative Anaerobic conditions are by characterised the lack of oxygen. Anaerobic degradation occurs anywhere in Anaerobic treatment 3.3.6 the until compostingcontinues process phaseofthe isreached. stabilisation third process This again. up back speeds activity biological as temperature in increase asambientairisintroduced, butisfollowed temperature by arapid the pilelowers the matter. Turning decomposed partially introduce oxygen, to andredistribute intervals pileatcertain the turn and to pile, the allow to for oxygen passthrough to ofmaterials textures have to amixofdifferent important To itis 10% this, aerobic achieve than isoccurring. that ensure to airgreater of the anoptimal oxygen volume, content with atleast 20% spaceshouldrepresent ofthe pore The free 58 Equation 3.15: CH CH Equation 3.14: 2 3 3 + CO COO OH +H 2 - gCH +H 2 gCH 2 O gCH 4 +2H 4 +H 2 4 O +HCO 2 et al.,2011).et nature lessenergetically favorable the Dueto O 3 - 2 , CO , 2 , formate, methanol, methylamines, and methanol, , formate, iue31 Theprocess ofmineralisation andimmobilisation ofnitrogen intheenvironment. Figure 3.10 hydrolysis process. this during isreleased as ammoniathat in FSispresent ofnitrogen Themajority isdegraded. matter organic andthe dieoff asorganisms forms bioavailable into back released and mineralised then is Nitrogen structures. and components cellular microbial as such molecules organic asitisboundupinto it isutilised,nitrogen bioavailable isimmobilisedandnolonger 3.10, As shown in Figure once growth. use during to for of nitrogenavailable microorganisms are forms environment. Inorganic the into discharged shouldnot beindiscriminately that potential pollutant canbecaptured for benefi that nitrogen. Nitrogen isanessentialnutrient cial enduse,andisalsoa highinammonia bevery to aspectofFSM,asFStends Biological nitrogen cycling isanimportant Nitrogen cycling 3.3.7 Biogas reactors at 2iEinOuagadougou, Faso Burkina (photo: Linda Strande). Figure 3.9

(microorganisms, Organic matter protozoa) mineralisation immobilisation NH 4 + ; NO 3 - 59

Technology Technology bacteria that can oxidise NH that bacteria anammox with BOD without conditions anaerobic in occur also denitrifinitrifican and cation cation Simultaneous systems. denitrifying – nitrifying for requirement alkalinity total the calculating when NO Where: N NO =nitrogen oxide NO 3.57 g of alkalinity as CaCO as alkalinity of g 3.57 addtion In Eddy,2003). and (Metcalf reduced nitrate of g per needed is BOD of g 4 that estimated is it but calculated, be can values precise More occur. denitrifi to for cation BOD adequate is there ensure nitrifi includesboth that When designingasystem cation anddenitrifi to cation, itisimportant N Phosphorus cycling Phosphorus cycling Equation 3.18: NO shown inEquation 3.18. forms intermediate nitrogen oxide products. Denitrifigaseous some combination of the proceeds through cation generally of intermediate a series aerobes. The process happens through many facultative are of which bacteria, is 7.0-8.0. optimal pH range process and the heterotrophic and both autotrophic with The process occurs anoxic the inhibit 0.1-0.5mg/L than greater concentrations oxygenDissolved receptor. electron an as air. Anoxic environments isused the nitrogen to releasing low are inoxygen, andnitrate thereby gas nitrogen to ofnitrate reduction happens inanoxic the environmentsBiological nitrogen removal with Denitrifi cation g of alkalinity as calcium carbonate (CaCO 1mg/L.Thenitrifi than dissolved isgreater oxygen concentration the that cation process 7.14 requires (7.0), below pH6.8.Sincenitrifi butbecomerestricted cation isanaerobic process, itshouldbeensured 10°C. The optimal pH range is between 7.5 and 8.0. Reasonable rates of nitrification occur at neutral pH 2003). forThe optimal nitrifi temperature process becoming ineffi the cation is 28˚C, with cient below rely onnitrifiand potential for toxic compounds that whendesigningsystems cation (Metcalf andEddy, nitrogen concentration, biochemical oxygen demand (BOD) concentration, alkalinity, pH, temperature, 3.16 andEquation 3.17. considertotal to important Thisisasensitive biologicalprocess anditisthus asshown inEquation nitrate, to oxidising nitrite oxidising bacteria followed rapidly by nitrite nitrite, nitrifi oxidise ammoniato isanaerobic,cation, which autotrophic process. Ammoniaoxidising bacteria biological through canbeoxidised nitrate to mineralisation, during isreleased Ammonia nitrogen that Nitrifi cation 60 acidorbase ofthe ismostly moleculescomprised asphosphates; present inFSandexcreta Phosphorus environment. the into discharged shouldnot beindiscriminately that is alsoapotential pollutant canbecaptured for benefi that isan essentialnutrient nitrogen, phosphorus As with cial enduse,and Equation 3.16: 2NH nitrifiinhibit the cation process (Metcalf andEddy, 2003). (Metcalf and Eddy, above 100 nitrate ammonia to concentrations 2003). Free mg/L at pH 7 can also to N to 2NO Equation 3.17: 2 2 =nitrogen gas. O =nitrous oxide 2 3 2 - - . = nitrite =nitrite =nitrate 3 - 2 2 NO g - +3O +O 4 3 + is regained during denitrifi cation which should be taken into account into taken be should denitrifi which during cation regained is 2 2 to N to + Nitrobacter g2NO +Nitrobacter 2 +Nitrosomonas g2NO - gNO gN 2 , utilising NO utilising , 3 ) for each gram of ammonia nitrogen (as nitrogen) converted ofammonianitrogen (asnitrogen) converted ) for gram each 2 O gN 2 - 2 3 as an electron acceptor, also getswhich reduced

-

2 - +2H 2 O +2H +

FS treatment is due to removal by plants in planted drying beds. bydrying plantsinplanted removal isdueto FS treatment Temperature processes treatment functionasdesigned. that ensure to considered be allbiologicalprocesses, needto which affect They FStreatment. during isachieved reduction pathogen that ensure to mechanisms, interrelated ofallthese have to anunderstanding is important 2. It inChapter detail inmore presented are ofpathogens covered. are mechanisms Types and chemical from physical, biological, ofpathogens inbiologicaldie-off result that mechanisms section,the In this Pathogen reduction 3.3.8 Figure 3.11 Pilot scale co-composting facility with faecal sludge with faecal andmunicipalwaste Pilotco-composting facility scale inBangalore, India(photo: Figure 3.11 inactivation. lesstimeisneededfor increases, pathogen temperature as well Asthe aslimetreatment. 3.11, co-composting asshown inFigure inprocesses asthermophilic Thisisachieved such denatured. of60˚Cwhencellproteins above andnucleicacidsare temperatures inactivated are Most pathogens Al be increased through biological dephosphatation, or through chemical precipitation with FeCl with precipitation chemical orthrough biologicaldephosphatation, through be increased can This microorganisms. by up During taken is phosphorus 10-30%of about processes, treatment biological potential. redox and due to off gassing or uptake, leaching like nitrogen, as the plant soluble inorganic form is adsorbed in is not Phosphate and released. lost mineralised are bound phosphates pH, the material, of organic sludge. degradation During mineralisation, sedimentation, complexation, precipitation, assorption, such processes intreatment dependsonfactors ofphosphorus The fate proteins). nucleic acids,phospholipidsandphosphorylated form of orthophosphoric acid (H oforthophosphoric form 2 (SO 4 ) 3 or FeSO or Chris Zurbrügg). 4 which are used for wastewater treatment. The greatest loss of phosphorus during during lossofphosphorus Thegreatest treatment. usedfor are wastewater which 3 PO 4 ) or phosphate (PO 4 3 - ), or as organically bound phosphorus (e.g. bound phosphorus ), or as organically 3 or 61

Technology Technology 62 Verstraete, 2001). (Weemaesand inactivation adequate in result not does 10°C than less temperatures at Storage 20˚C. at two and years 35˚C, of temperature ambient an yearat one to forup FS of time storage recommends (2009) example, Niwagaba For ambienttemperature. alsodependsonthe reduction for pathogen duration storage Therequired years. to months viabilityfor several andcanmaintain persistent, (Feachem average days 50 on for coliforms survives Faecal and spp. days 30 Salmonella for example, For months. 2 and week 1 between survive only can most bacteria conditions. In faeces, time in adverse have survival a limited as they reduction, pathogen in canresult sludge oftreated storage beds)orthe drying (e.g.planted oftreatment The duration Time 3.4 CHEMICAL MECHANISMS CHEMICAL 3.4 reduction. pathogen considerdownstream whenemploying to steps treatment pHcontrol for important and itistherefore However,pHcanalsoupset reduction. composting the andanaerobicpathogen digestion processes, below pH3andabove pH10.survive way, Inthis additionfor chemical pHcontrol in canresult can few of 2-3pHunits,andvery arange within andgrow canonly survive Most microorganisms pH ofUVradiation. penetration andturbidityprevents matter organic high the as surface, the at occurring only likely most therefore is mechanism This treatment. FSduring the must penetrate beableto light rays the be effective, to mechanism for this that remember inactivate effectively to shown been has light UV 1998). al. , et (Borrely molecules viaphotochemical reactions DNA denaturing by pathogens inactivates effectively nm 300-400 of range the in radiation Solar/UV UV water. available ofthe reduction the dueto disinfection to alsocontributes storage Further has aneffect. desiccation pointwhere gets below content acertain water beds)ifthe (e.g.drying ofpathogens die-off the to contribute therefore technologies 2001). Alldewatering conditions(Carrington, drier in much activityof0.9,whilesomeyeast andeggssurvive underawater 1, cannot survive andmost pathogens activityof hasawater water sameconditions. Pure underthe water ofpure pressure vapour water the to sludge of the pressure vapour ofwater ratio Water by the activityisrepresented for survival. water need asmicroorganisms active indesiccationordehydrationreduces pathogens, resulting Evaporation Desiccation must beconsidered. ofallpathogens fate the fraction, solids the with eggs partition of Helminth majority the protozoan cysts). Although types of bacteria, different (e.g.viruses, ofallpossiblepathogens representative not are necessarily bacteria indicator al. , 2008).However, et (Pepper bacteria asdoes90%ofindicator solidfraction, the with eggs remain al. , 1998). ofHelminth settlingdue to (Heinsset In fi majority beds,the fraction drying with occurs liquid that ltration the from separated are eggs helminth the of 50% about tanks, thickening and settling In inFSsystems. solidsfraction the with sorborsettle, to andhencepartition eggstend Helminth Sorption beneficost andthe oftreatment, becarefully weighed. needto ts therefore asignifi canrepresent FS.Theadditionofchemicals and stabilise pathogens overall inthe cant increase fladdition ofacationic the polymer increase to settling effiocculation and the inactivate ciency), or to physical (e.g. mechanisms ofother improve FSto performance Chemicals canbemixed with the , 2009). However, it is important to to al.,2009).However, et itisimportant ponds(Maïga stabilisation E. coliinwaste , 1983). Helminth eggs however are very al.,1983). eggshowever very are et Helminth rapidly enzymatically transformed to NH to enzymatically transformed rapidly NH of concentration the increasing ofpH,thereby inadecrease soilitwillresult the FSisappliedto treated The total aqueous NH The total Equation 3.19: by Equation 3.19.based onpHcanbedetermined bacterial inactivation are that NH that are inactivation bacterial (2013), inVinnerås for possiblemechanisms not are mechanisms yet As described fully understood. exact butthe microorganisms, atinactivating aqueous ammoniaiseffective that It iswell established Ammonia treatment 3.4.2 andlimescaling. ammonia odors process include this with canoccurover time.Concerns pathogens ofbacterial regrowth noted that limeisaddedinexcess. Itshouldalsobe that requiring therefore pHwilllower again, the reaction, Helminth inactivating settling and increase to effi has eggs. also The been reaction documented reduction, ciency. initial the However, pathogen after increasing thereby 2001), (Andreasen, 60°C to up temperature the increase can that reaction exothermic an in result also will it used, is (CaO) lime quick andproteins, alsohydrolysesaswell carbohydrates, reaction asammoniafrom aminoacids. If fats, causeputrifi that factors dueto an odorreduction Thischemical ofpathogens. cation, andinareduction 12, microbial pHto activity. stops the which the in Thisresults quantitiesFSraises of adequate oflimeto polisheffl plants,andto treatment from liquid streams inwastewater phosphorus uents. Theaddition precipitate additives Limeisalsousedto more willberequired. dewatering, to outprior If carried post-dewatering. or pre- either FS, of stabilisation the for used be can lime, as such additives, Alkaline Alkaline stabilisation 3.4.1 by adding potential determining ions (strong acid or base) that reduce the total surface charge. Polymers Polymers charge. surface total the reduce ions(strong acidorbase)that by addingpotential determining Coagulation andfl or between particles, abridge form by that achieved occulation are addingpolymers charge. surface their with together particles, ofthe characteristics hydrophobic orhydrophilic basedonthe Theseadditives chosen are enhanced sedimentation. fl larger form other, each with comeincontact to allowing them achieving ocs andsettle, thereby in suspension. In coagulation and fl stable them particles, destabilise occulation additives added that are making charged, be settlingnegatively to tend gravity notare removed through that Colloidal particles Coagulation andfl3.4.3 occulation to avoidNH to lossofgaseous nitrogen concentration (NH nitrogen concentration It isaqueous NH phaseofdevelopment. research in the al.,2009),butapplicationsfor still FSare andcompost al. , 2007), et et (Adamtey (Pecson sludge sewage al.,2008), et (Vinnerås inurine hasbeenshown Ammoniadisinfection beeffective to fully understood. still are mechanisms not the ashelminths, such organisms, butfor larger ofRNA, cleavage the due to is inactivation possibly cytoplasm loss resulting of in (K). alkalinisation of the a Viral potassium critical of ammonia is 9.25 (the pH where 50% is NH is 50% where pH (the 9.25 is ammonia of (Vinnerås, 2013).(Vinnerås, Ammonia can be added as as aqueous NH aqueous NH for specifi each empirically determined the stable, pHremains Aslong asthe ofconcern. c organism 4 + , which isbenefi, which cial asafertiliser. 3 will remain constant and pathogen regrowth will not occur (Vinnerås, 2013). willnot occur(Vinnerås, Ifthe regrowth andpathogen constant willremain 3 that is responsible for microbial inactivation, not the ammoniumion(NH not for isresponsible the microbial inactivation, that NH 3 ,% = 3 concentration will also depend on temperature and total ammoniacal and total will also depend on temperature concentration 3 3 +NH . At this stage, the time for inactivation of microorganisms needs to be needsto ofmicroorganisms timefor inactivation the stage, . At this 1+ 3 [H denaturates proteins, destroys membrane potentials, or causes rapid proteins,potentials, orcausesrapid destroys membrane denaturates 4 10 + + ). For NH ). For ]/K 0 a 3 . The treatment needs to be carried outina confi becarried needs to . Thetreatment ned space 3 3 disinfection to be effective, the pH has to be above 8.5 above be to has pH the effective, be to disinfection and 50% is NH is 50% and 3 solution, or urea (CO (NH (CO urea or solution, 4 + ), and the percent NH percent ), andthe 3 concentration concentration 2 ) 4 2 + ), which is ), which ). ThepK 63 a

Technology Technology Carrington, E.G. (2001). Evaluation of sludge treatments for pathogen reduction –fi reduction E.G.(2001). for treatments ofsludge pathogen Evaluation Carrington, E.Communities. nal report. Del E.S. Mastro,Sampa,(1998). N.L., and processing Borrely, M.H.O., of A.C., Somessari, sewage Radiation S.I., Cruz, by Edited Utilization. Disposal, Processing, Biosolids: into Sludge stabilization. Chemical (2001). P. Andreasen, an of part as region irrigated an -Guidelinesfor computing M.(1998). crop water D.,Smith, Crop evapotranspiration L.S.,Raes, Allen, R.G.,Pereira, over method coefficient crop dual FAO-56 the Using (2000). R.G. Allen, (2011). R.,Baidoo,M.F. inGhana:Asolutionto Arthur, infour publicuniversities from sewage generation Biogas co- N-enriched of Cofistorage and Production N., (2009). D. Adamtey Forster, S.K.A., Danso G.K., Ofosu-Budu O., e 3.5 BIBLIOGRAPHY constituents. other oxidation ofthese willbeusedupinthe chlorine the for FS,orliquid disinfecting effl isnot effective load. Chlorination as highorganics, contain uents that oxidation process isnot specifi organic total considerthe to important microbes, anditistherefore c to The asithasahighcapacityfor oxidation, cellmembranes. damages which microorganisms, to constituents in effl and other load, temperature, is toxic load). Chlorine organic uent (e.g. remaining pathogen concentration, time,chlorine includecontact designparameters Important liquid form. asolidor andcanbeappliedineither ofdisinfection, most widely usedmethod isthe Chlorination asfi meanssuch mechanical through but itisalsoachieved ormembranes. lters UV,and ozonation, chlorination, include disinfection of forms Chemical sterilisation). as to referred is elimination(which not atotal discussed inChapter 10. ofpathogens, areduction to refers Disinfection enduse, as intended for levelsof treatment the andappropriate ofadequate context inthe considered to in prior fi reduction a treatment nal achieve Liquid of FS treatment. effl to form further and is not a primary pathogens step require ‘polishing’ be also needs to uent treatment a typically as considered beds be should drying Disinfection disinfection. or tanks settling from effluents Liquid is treatment). and (e.g.ponds,wastewater references treatment andwater specifiFS, inwastewater covered indetail not to is c it as book, this in detail in covered efflnot liquid is of uents Disinfection ofliquidefflDisinfection 3.4.5 uents isnecessary.scale testing and pilot- laboratory, from manufacturers, FS, information to technology Totreatment. this transfer sludge wastewater to relates available iscurrently simple that settling Theinformation jartests. with laboratory the in determined is dosage the general, In alkalinity. and concentration, solids source, pH, age, sludge considerare aspects to use,important to chemical solids.To appropriate total selectthe the and lime can increase the total solids of dried sludge (increasing bulk), whereas polymers do not increase Iron salts polymers. lime,alum,andorganic chloride, Commonadditives includeferric performance. enhance inSection3.4.3to asdescribed ofdewatering physical to forms outprior can becarried ascoagulationandfl samephysical properties Chemical conditioningisbasedonthe occulation, and 3.4.4 Conditioning particles. adsorbedto are that polymers highmolecularweight with abridge orby forming polymer particles, to and non-ionicendsofthe anionic between the bridge a work They forming chemicals. based by synthetic or either natural be can 64 Luxembourg. 33(1–2),p.3-21. inNuclear Energy Areview.sludge. Progress Vesilind.L. SpinosaandP. A. IWA . Publishing,United 56,FAO, Paper and Drainage Rome. FAO Papers. Irrigation andDrainage FAOrequirements. Irrigation study. ofHydrology 229(1),p.27-41. intercomparison Journal evapotranspiration 35(7),p.3086-3093. Biomassand Bioenergy risk. potential health compost. Waste 29,p.2429-2436. Management eme, . Vrtat, . 20) Ohr ramn tcnqe. lde no isld – rcsig Disposal, Processing, – Biosolids into Sludge techniques. treatment Other (2001). W. Verstraete, M., Weemaes, B.(2013). M.L., andhygiene In:Sommer, management. Vinnerås, inmanure Sanitation S.G.,Jensen,L.S.,Christensen, inhumanurine andviruses ofbacteria K.(2008).Inactivation C.,Nyberg, Niwagaba, B.,Nordin, A., Vinnerås, Utilization. and Disposal Processing, – Biosolids into Sludge stabilization. to Introduction (2001). P.A. Vesilind, treatment sludge of operation optimal for model Dewatering (2012). J. García, I., Ferrer, A., Argilaga, E., Uggetti, of Effect Beds: Reed Drying Sludge pilot-scale in mechanisms (2011). Dewatering V.A. Tsihrintzis, A.I., Stefanakis, Biosolids.Technomic (1997).Spellman, F.R. Publishing,Lancaster, States. United Dewatering Pepper, I.,Gerba,C.,Gentry, T., Maier, Microbiology, R.(2008).Environmental Elsevier. pH, and ammonia of temperature, Jimenez, B.E., Nelson, K.L. The (2007). effects J.A., B.M., Barrios, Pecson, regime impounding percolate and depth layerInfl sand (2009). of D. uence Koné, T., Koottatep, A., Panuvatvanich, of University Swedish Thesis, PhD Urine. and faeces Human for Technologies Treatment (2009). C.B. Niwagaba, Romandes, Universitaires et Polytechniques Presses nature. la de science une Hydrologie, (2004). Higy,C. Musy, A., eds. F.L. Tchobanoglous, disposal,reuse. treatment, G.,Burton, Metcalf and Eddy(2003).Wastewater Engineering: Pearson microbiology. Brock’s D.(1976). Mara, inHot Wiley, Climates. Kingdom. Treatment London,United (2004). Sewage S. M. Pérez, C.R., Fernández, J., Parker, J.M., Martinko, M.T., Madigan, by Edited Utilization. Disposal, Processing, – Biosolids into Sludge Characterization. (2001). N. Dichtl, J., Kopp, Kim Y., Parker W. (2008). A technical and economic evaluation of pyrolysisthe of sewage sludge for productionthe of Huisman, L.,Wood, W. E.(1974). Slow sandfi (Vol.ltration 16). World Geneva. Organization, Health (1998). sludges treatment of faecal forsystems and S.A. pond the forSolid systems separation the Heinss, Larmie, U., andWastewater Management. AspectsofExcreta R.G.,Bradley,Feachem, D.J.(1983). andDisease–Health Sanitation Utilization. Edited by Vesilind.Utilization. Edited L.SpinosaandP. A. IWA Kingdom. Publishing,United UK Oxford, (In Press). Wiley-Blackwell, Management. and Treatment Recycling, – Waste Animal (eds). T. Schmidt, Water 42(15), Research anddilutionrate. depending ontemperature p.4067-4074. by Vesilind.Edited L.SpinosaandP. A. IWA Kingdom. Publishing, United wetlands. Water 46(2),p.335-344. Research 172(1), Journal p.430-443. ChemicalEngineering parameters. design andoperational Water sludge. eggsinsewage 41(13), Research ofAscaris inactivation onthe p.2893-2902. concentration (10), p.2623-2630. invertical-flon nitrogen transformation Watersludge. wetlands faecal 43 treating Research ow constructed Science,Uppsala, Sweden. Agricultural Lausanne, Switzerland. BookCompany.McGraw-Hill Jersey,Education, Inc.,New States. United Vesilind.L. SpinosaandP. A. IWA Kingdom. Publishing,United Technologybio-oil. Bioresoures 99(5),p.1409-1416. tropics. EAWAG.in the Switzerland, EAWAG. Dübendorf, TheWorldWashigton, D.C,USA, Bank. 65

Technology Technology 66 treatment andinwhich reduction for responsible pathogen are mechanisms Which 3. Does composting rely on physical, What are mechanisms? or biological chemical treatment 2. Give two ofphysical, examples each andwhattreatment andbiologicalmechanisms, chemical 1. End ofChapter Study Questions technologies do they exist? dothey technologies for required effi are conditionsthat three cient composting? to. relevant are they technologies