WO2012105847A1

WO2012105847A1 - System and method for the treatment of municipal and industrial wastewater and sludge

Info

Publication number: WO2012105847A1
Application number: PCT/NO2012/050001
Authority: WO
Inventors: Svein STORÖ
Original assignee: Salsnes Filter As
Priority date: 2011-02-04
Filing date: 2012-01-11
Publication date: 2012-08-09
Also published as: NO332969B1; NO20110201A1

Abstract

System and method for treatment of wastewater and sludge at municipal or Industrial wastewater treatment plants. The system includes one or mere rotating belt sieves (18) arranged for simultaneous primary treatment of wastewater and dewatering and/or thickening of primary and biological (secondary) sludge. The rotating belt sieves also facilitate nitrification in biological reactors.

Description

System and methad for the treatment of ^municipal and industrial wastewater and sludge

The invention relates to a system for simultaneous primary treatment of wastewater and dewateringand/or thickening of primary and biological (secondary) sludge. at municipal or industrial wastewater treatment plants according toithe preamble, of claim 1.

The invention also relates to a method for simultaneous/primary treatment of wastewater. and dewatering:and/or thickening of primary and biological (secondary) sludge at municipal or industrial wastewater treatment plants, according to the preamble of claim 9.

Background

Traditionally ftne mesh screens and ^:sievesⁱhave^;bee;n;.used^'fo.r pre-treatment, onasithe .only treatment at.smailer plants:that:discharged wastewater to the ocean.. emoval Efficiencies reported for screens and sieves with less than 1. mm ©penings, were only typically 2 to ¾ % for organicmatterand only 10 to 20¾:fprtotal suspended sdlids-(TSS). The.^:effect was mainly

Worldwide, TOOstof ^

primary treatment.

From lJSZ00919 75iVit iscknpwn ¾ method .of tFeating a mixture of microorganisms containing phosphorus and magnesium,

and magnesiUnTwHich;are theR^:ta^;pped d as.the:mi¾ure¾

magnesiumrich liquid. and phdsphdrus and magnesiumreduced treated mixture. This treated mixture is placed in an anaerobic digester.where ammonia is/farmed :but combines er littlewith. phosphorus^r m;agne5ium¾s¾^

the high iammohia^tmixtureiis dewatere ¾ produce an ammom^"arich ^:¾ is combined with the hbsp o^ one;preferred embodimertt^::a¾seable struyite product is harvested from this combination. Additionally, the production of nuisance struvite in the anaerp;plc.:diges^ prior art waste_:;treatmerit methods. liS20G4i6¾019Aidescribes^;a sewage f re¾meh6sysi¾m ¾ a wast stream fir separated into a primary sludge and rwater effluent, and the primary sludge is anaerpbically digested and dewatered to. prodtlce a Glass .A biosolid.^'The'water effluent is.aerd^ically digested and separated ;to provide a waste activated sludge. The waste activated sludge is heated in a two- stage process with steam injection and indirect steam before it is passed to a hydrothermal process, The^!:p| of the treated waste actiyated:

stripped-and recovered as an ammonium :salt. A . low nitrogen ^stream with volatile fatty acids and sd:lub!e.-o¾^ during anaerobic digestion provides energy for heating the waste activated sludge for the hydrotherma! process, and reject heat from the hydrotherma! proeess hea^'ts the::primary sfudge-for thermophilic anaerobic digestion.

From EP115.60.15A it isvkhown a sludge wastewater treatment process which comprises:.(l) discharging activated sludge and water from a first basin to a settlement basin; (II) subjecting sttm icff the- activatecksludgeto wemb|3ne-fiitratloWin-;Wh(dh^' flltriite¾-idra n;ofP;.-¾iwf ^'{.ΙΙ|) returning some of the -activated siudge to .the first basin. An Independent claim is also included for an;assembly with.-a low pressure , membrane f ilter which^'is_;eontinuaily exposed to the . turbulent passage of fluid everthe membrane;in:a membrane module.

US5976375A describes a proeess^:iorreducing_:^

treatment ofpulp -and paper

sludge. (RAS) prior to its return.into the .aeratio n tank. The conditioning is typically performed within the siudge return line¾nd^: invdives^;RA& exposure to 3 waste acidic eft luent originating from passes

through an' aerobici bioio ica I oxidatio h zone fo r oxid iziagiBSD an co nve rtingia m mon ia nitrogen _. ^'to ^;nitrate^ mixed with effluent from an anaerobic/anoxi zone receiving;^

removal.

i_!S535:653i7A_: describe^

.essentially nos!udge remains for disposal,

activated ;sludge solids-in anaeration tank. Ihe mixedliquorfrom the arifcis hen rapyet Qsa :Clar1fier^;setttihg iahk. :ft^

returned to an aerobic digester and treated for about 16-24 hours. The aerobic digester can be a batch.:unit:o;r;a. continuous^pro^

From¾S5447633Ait is known a two-stage . activation plant, where a part of the activated sludge {first siudge circuit) from the first stage is transferred to the second stage and a part of the

is¾rans¾tredtp:te

tHa mixed bipcenoses areiformed in both stages. The biornassitb ½ denitrified :fra

;stage.:istransferred to the second stage by the first sludge circuit and the biomassto be nitrified fromthe second::St3ge¾^ carbon compounds are decomposed but nitrogen compounds may be removed by nitrification and de-nitrification in both stages.

US5032289A describes an offshore sewage treatment facility or sludge facility being serviced on a ship. The:fad!ity. is totally and/otpartiafly energy selfsufficientby means of . utilizing methane -gas enerated:^;by the;processing plant. The. processing facility allows forprimaryand'secondary wastewater treatment and digestion, dehydration of sludge orsdlids, generation of methane gas, drying of sludge or sQlids and pelletization of sludge w1th¾nd products .or¾y-products of

with potash, or theory^, sludge may be manufactured into.blocks suitable for the construction of buildings.

From US49_.1584QA it is^:½iown an:improved . processifor the treatmentof muniGipal waste and particularly to the reduction :of orgahic siudge-generated in the.biologicai digestion. of organic ^■material. ln the conventional'processes the waste containing organic matter is contacted with an oxygen containing gas in the presence of biologically active organisms tinder conditions to produce ^:biomass.which,.::on separation, forms sludge. Abortion :of the;Sludge: is Often: returned to the

?aerdbic digestioreprocess. Thrsiinvention relates to an improvement^'for/Sludge reduction in these processes wherein a portio_.ri

in an autothermal aerobic digestion zone. The effluent from the autothermal aerobic digestion ¾one usually . is returned to!theJriiy In anotherembodiraentOf ¾ sludge is charged to an autothermal; methane and the effluent from the autothermal anaerobic digestion process subsequently icharged^'ito tneautptherm

•jwffter; B -these combinationspne^

one can Operate.under conditiori5^;such:triat;there is;no net-generation of kludge.

US4818405A describes that municipal sludgers converted from an.ehvironmentai problem into isoil-ame dmentand^

generate electricity and partially to dry the; cop^

_.the_.dryer is¾sed to maintain the temperature in the digester at approximateiy 105 DES to 130 DEC F. Heavy metals are removed so that the dried sludge can be safely used as a soil amendment. ; From^:EP029!665¾\it is:

sludge. The ease with which biological sewage sludge, particularly digested sludge, can be dewatered is mproyecrif the^sewage sludgeistreated with hydrolyti ehzyrnes such as

carbohydrases (amylases, cellulases), proteases, glycoproteinases and/or lipases, followed by the ^addition of a synthetic flocculant, particularly a cationic polyelectrolyte. These prior art solutions: have- many disadvantages compared to the present invention:

- larger energy costs, . due/to. high power consumption. of oxidation ditches and aeration tanks,

- none :br. very: low primary sludge . roduction,

- "higher organic and nitrogen load to biological treatment,

- larger volume Of aeration tanks,

- : igher biological sSudgeproduction,

- lower surplus-sludge concentration,

- hjghersurplusisludge volume,

- higher oxidation ditch JvlLSS-concentratlon,

- higher RAS¾ow,

- higher WA¾prod uctton,

- lower overall capacity.

It should also be mentioned that there- exist lants using^'CEPT (Ghemically . Enhanced Primary

15 Jreatraent) or DAF (Dissolved: Air Flotation} for primary treatment but these.:piantsido_. not have¾ roxatEngrsieve as will -be theicase fer the present invention. They neither provide sludge dewatering.

¾ isinot:known¾;prop:Osed ihpr orart or system: for simultaneous primary treatment and dewatering and/or thickening of primary and .bio!ogical.:(seco^:n.dary:). siudge system.

Object.

The main object of the invention is to provide a system and a method which partly or entirely ,25: solv.es hedisadvantagesO.f prior-art,. and to provide a cheaper:and more: effective system

compared to prior art.

it is further an object of the invention tdprovide- a system and a method which provides: simultaneous pnmary treatment:ot wastewater an :^ thlckeriing-df primary and

Biological (secondary! sludge at municipal wastewater treatment plants.

30; It is also.an object of the fnventionto utilize afine mesh sieve.systemto provide:_:sim:ultane.o:us ; primary treatment of wastewater anddewa

(secondary) sludge.

It is also an object that of the invention ^

and/or wash water- from :_:backwas.hi ng of sand filter if the system has tertia y treatment_s for 35 example for phosphorus removal or improved solids removal fsand filter). ^: Further, it is an object of :the;present inv.ention to reduce the space needed for a system for treatment of. municipal and industrial wastewater and sludge due i to removing or replacing equipment for dewatering and/or thickening secondary sludge.

Finally it i an^object of the invention to dispose sliidge-at_:an early stage :for maintalning hfgh energy in the sludge, so that the sludge may be used for producing bio energy.

The invention

A system. according to the invention is described in elaim.l.. Advantageous features of the system are described in claims 2-8.

A method according . to the invention is described in claim .9. Advantageous features f the : method are described in ciaims.10-16.

Worldwide, most of the iarge biological WWTPs have. rimary . treatment. However, a lotOf the :.5ma11erbIo.logi.cai WWTPs are designed withoutprimary treatment. Many-Of these smaller plants .arejoxidation ditch type/plants for emoval . of organic matter. These_:,plantS:include a coarse;Scra.en fonhandling the infJuent-wastewater and a biological treatments/system which consist of an oxidafton diichwith^ is-pumped ^■from the bottpm Of the final clarifiera

sludge (WAS) is disposed. Theiinal clarifier also :. o.vldes the .effluent wastewater._.

A converitional act ivated-sludge plarvtferthe removal of _:organ|c^;rnatter mcliides one:Gr mpre ¾co rse screehsand:sand and grit trapsfe handlingthe influent w^

provided to one.or more ..activated . sludge: aeration tanks_:and nextto means'for^econdary and/or te.rtia ry biological and natural removal treatment. The; r¾S ^'f rom the^means: f rom. s^cdhda ry and/or tertia ry biological a nd natural removal treatment is bro ught back to the activated sludge aeration itanksandthe . WAS is. disposed from^;the means . for se natural, removal treatment, which also provides the effluent wastewater.

The new and inventive feature of the invention is to introduce a rotating balt.sieve, also called ine mesh sieve, to these above , described systems arid y.af^'iants.df these, a nd the results ithe : introduction of the rotating belt sieve result in.

By introducing a rotating belt sieve in. a system/plant like the ones mentioned and the like, simultaneous primary treatment of wastewa

:biblogical (secondary) sludge atmunicipal or industrial waste ater^;treatment syste_.ms/pl-ihts can- be provided. The WAS can be returned to the rotating belt sieve instead of being disposed.

This has many advantages compared to prior art solutions: - considerably lower energy costs, due to lower power consumption :df oxidation ditches and aeration tanks,

- high primary sludge production compared to none in prior artsolution,

- lower organic and nitrogen load to biological treatment,

- lower volume of aeration tanks,

- lower. iological sludge production,

- higher s.urplus sludge concentration,

- lowensurplus. sludge volume,

- lower oxidation ditch MLSS-concentration,

- lower RAS-flow,

- lower AS-produci ion,

- higher overall capacity,

- increased removal efficiency for TSS: and BO.D₅,

- higher-energy content waste of the biological sludge,

- provides, dewatering and/or thickening. of biological sludge without using, chemicals.

The latter system described aboveiand. referred to as a conventional. activated sludge plant-can further be URgraded for nitrification^' by-1ncr-easmg^;:te

sdfficientsolids retention time.

By introducing a rotating belt sieve as described above, the same result is achieved in that the sludge yi^;e!d ;and -waste _^activated sludge production wiil.be sufficiently^{^}

retention time in:the;exjsting:aeration tanks that iwi!l be sufficiently longfor rtitrtftcaiicfrj to take place. Together with t e. other above mentioned advantages.

^ y th the system s^

convehtipna! systems plants, resulting in that this;spare capacity may:bettsed¾o connect more population equivalent to the treatment system/plant.

If the new- onriectiohs- have the_/sa me: wastewater concentrations as the existing!connections, ihe¾rgahte and . ydraulic ad on thetreatmeht; system/plant can be increased by about 30 % before the capacity of the final clarifier is reached. The existing aeration system will still have some spare capacity.

If the hydraulic load from new connections-is compensated for by similar reductionsTn infiltration and inflow elsewhere due to upgrading of the sewer system, then the load of BOD and TSS may .be increased by 45 to 50 %:hefore the capacity of the treatment system/p!ant js-reached. However, if the:aeration system originally had some spare capaci

10 %, then the load of BOD and TSS may be increased by 60 % before the capacity of the treatment system/plant¹ is reached. A system/plant like the ones describe above -usually includes an inlet chamber wherein the rotating belt sieve runs. To further emphasise the overall efficiency of the system/plant, the influent wastewater can b measured by suitable means and the wastewater leve!-ΐη the inlet chamber can be measured by suitable means, so thatthe rotating belt-siev&can be controlled by utilizing information on: how much influent wastewater is supplied to rotating'bel sieve a any time, and the variations of the fluid level (rise-time) and particle concentrations at any time in the inlet chamber. By this way, the rotating belt sieve,ean be controlledto create as hick filter mat.on the rotating beit.sieve ;as ossible, to achieve as good cleaning-efficiency/particle reduction as possible, and at the same time the information: is used to control the rotating belt sieve to avoid that the inlet chamber/rotating belt sieve overflows. The overflow is generally brought back. to the inlet and-will then provide lower capacity, if. not, the cleaning. efficiency/particle . reduction will be redueed because uneleaned fluid-gdes directly to the. outletand iticreases he.pollutioh or¹ because the overflow (normally for.larger systems piants with several^' cleaning/treatmentsteps

(biology/chemistry/membrane) goes to the next cleaning step and overloads the system, or that the^: operating costs increase because increased supp!y of oxygen becomes necessary.

fluid level :{Fise-time) and particleiconcentrations in the inlet chamber, the. rbtattng-b.elt sieve- an be controlledto -achieve aifltermat as . thick as possible^The conditions and settings for the

Thisis well.tfesc ibediin :WO2009Q91260~"Meiht>ii and system _:for particle recJuction'', i the^ name.o^'f:theapplicaht..WO2DQ909 260 is indud.ed:herein . as whole.

The. system .preferably further includes ^{^}m

Patents No.310182. and ^:178608,¾:¾he name of the ap te

mat as possible it is important that the means for removing sludge do not include mechanical contact on the article side of he dtating belt-sieve, as a mechanical contact at the particle side will resujt in thatthe. particles: are_; ^:erushed/d

whichicould resultinthatthe ro^ particles-through the rotating beltsieve .and thus- reducing the: rate of pa rticte

escapethrough he rotating belt sieve. to the outlet, water, or-jacking::hydra,ulic^: _;capaiCity:.so that uncleaned fluid overflows. ^'!t..is.therefore,a great sdvantagethatthe. means .used for .cleaning arfe of a type as described in the Norwegian Patents No. 310182 and 178608, in the: name, of the applicant. These are known solutions which will not be further described herein, but the

NorwegianPatertts No.3101S2 and. 78.608 are included herein as whole. The system is preferably provided with :one or more, sensor means¹ for measuring conditions at different positions for controlling the system, such as total suspended solids, waste activated sludge,, return activated sludge, BGD_S concentrations and the sensors mentioned above.

The system can also include meanstor further dewatering and/or thickening of dewatered and/or thickened sludge by means of, for example, a simple screw press or a filter press or other suitable, dewatering methods.

The system furfher ihcludes a control unit for controlling the performance of the rotating belt sieve,^" based on measured. conditions, such as a.sludge dosing method, e g. based on . that.primary sludge volume: should always be larger than the volume of waste activated sludge.

Even though it above is describedihe^use . of active-aeration sludge tanks, the system according to the invention. can be used in biofilm systems/plants. There would then be no RAS, but the biological (surplus) sludge can be provided to the rotating belt sieve for dewatering and/or thickening together with the primary siudge.

Details and advantageous features of the invention wiii appear from the following example description.

Example

The-invention will beto be described in^detaitwith -references tothe-attached drawings, where;

Figure_: ila is;a flow sheet of a conventional wastewatertreatmen system piant,

Figure b fe.a flow she.et;ofa . astewater treatment system according to the invention,

Figure Za^b is simplified fiow sheet.o a^;conventio.nal activated^:sIudge system {plant^:for removal of organicmatter,

Figure 2 c isa^

a ccording to the

Figure 3 is anVexample of a biofilm system^plaritprovided with: a.fota:ting::;be t.sieve ^:acco.rdiri_.g to the invention.

Reference is now made to Figure la which shows a flow sheet of a conventional wastewater treatment system/plant in the form of a biological system/plant. A conventional wastewater treatmentsystem/plarit includes a coarse screen 11 fCir removing objects from influent waste.water.12 before it eriters a oxidation ditch with.surface aerators 13 for the removal of orgari)c:matter. After organic materiai is removed from the wastewater, the wastewater is supplied, to a fifial clarifier M which separates the wastewater into return activated sludge (RAS) 15, waste activated siudge .16 and effluerttwastewater 17. The.RAS.15 Is pumped ;.fro.m ;the:^bo.ttom of the final ciarifier 14 and back to the oxidation ditch 13. Reference is now made to Figure lb which shows a flow sheet of a:system for treatment of municipal and industrial wastewater and sludge according to the invention. As above the system includes an xidation ditch with aerators 13 and the final elarifier 14. !nstead of using a coarse screen li as above, the system is provided with a rotating be!t sieve 18, also called fine mesh sieve, which is arranged directly to the inlet 12 before the oxidation ditch 13. Instead of the waste activated sludge 16 being disposed, the waste activated sludge .16 is pumped back.to the . rotating belt.sieve 18, The rotating belt sieve 18 will here be arranged for both primary treatment of wastewater and dewatering. and/of thickening of both primary sludge and waste activated sludge 16. The rotating belt sieve 18 will, in this way dispose dewatered and/or thickened sludge 19. The system can of course have the coarse . screen .11 in . addition if appropriate. By this man advantages are achieved. The most important is . increased removal efficiency of organic matter. The second advantage is reduced sludge volume, as the sludge is dewatered and/or thickened.19. The third:advantage is reduced aeration consumption needed due to reduced oxygen ^demand in biological reactors, The/fourth advantage is increased ca.pacityvof the system, _;.as,the;,s_:ystem will-be able to process more wastewaterand^ludge dueto the_:prima

rotating belt sieve. 8. which" resuitin that the spare capacity can be used: to connect more populatiori-^:.equivalBnt!tio^: the treatmeifti-^Stem..-The-iotatln^belt jsieve.1-8 -will- also result invthat. the oxidation ditch :i3 nd the final.clarifier W

treatment system will have more capacity.

There are also considerable economic savings,asthis result in iowerisludge volame-which needs to ¾e:transporied^:away%orrt the; system and be.further processed. Asthe . operation ari maintenance cost aiso are reduced (for example power savings of the aeration tank), the total costs of the system/plant are considerably lower for a system according to the invention.

Surplus sludge concentration is considerably increased ^'and -surplus-sl udge volume is:

considerably reduced. The oxygen demand-is considerably reduced and theOxidation;dltch fvltSS- concentration is reduced. The RAS-flow and WAS production are considerably reduced and the primary sludge production is considerably increased.

Reference is now made to Figure 2a which shows a simplified flow sheet of a conventional activated. sludge system/plantfor removal of organic: matter. The system:inciudes:as above of one. or more coarse screens 11, but also sand and grit traps 20 are included. The system further includes one or more-activated sludge aeration tanks 21 for removing .organic matter and orie.o more means 22 for secondary and/or tertiary fciologlcal and natural -removal treatmefit for separating the wastewater into return activated sludge :(RAS) 15, waste activated sludge (WAS) 16 and effluent wastewater 17. The RAS 15 is pumped from the means 22 for secondary and/or tertiary :btoio_.gicaI and natural removal treatment and back to the activated sludge aeration tanks 21.

Reference is_^no madeto. Figure.2b which shows an upgraded conventional sludge system for nitrification. This can;be achieved by increasing the vo!ume.of the activated sludge aeration tanks 21. By increasing the volume of the,activated sludge aeration tanks.21 the solids retention time in the activated sludge production will be sufficiently long for nitrification to take iplace.

eference s-now made to Figure 2c which. shows another embodiment of a system for treatment of wastewater and sludge according to theinventton. As above he system includes one or mOre coarse screens:ll :but ;aiso:sand;^;and grit traps20 can . be included. The system further includes one or more activated -s!udge aeration . tanks 21 for removing organic matter and one or more means 22. for secondary and 6r tertiary biological and natural removal treatment for separating.the. wastewater into return activated sludge (RAS).15, wsste activatedisludge (WAS) 16 and efflaent..W3stewater l7. The: RAS:i5.is.pumped from :the means^' _;22 for secondary and/or tertiary biological and natural removal treatment and back to the activated sludge aeration tanks. 21. The system further includes. a rotating befesieve ¾ .^ -xalled^'-fine_;:mesh¾sleve -wMch ^'is_. arranged;,between the coarse screens ll/sand and grit traps 2O;an.d the -aeration tank 21. Instead of the AS.16;.being..dispQsed, the WAS .16 Is brought back to the; otating¹ bett sieve,:i8. The rotating' bel sieve iS ill here be arranged for both . rimai^treatment-Gf wastewater and dew.atering-and/or..thickening.of_:both primary :sludge and WAS 16.^;The rotating: belt sieve .18 wltl in this way dispose dewateredaRd/orthick efficiency of organic rh^'atten^^

thickehed .19. he. aeration consumption heeded is. educed due' to reducedioxygeri demand in biological reactors. This^mbodSmentalso- rovides as the sludge yield and WAS;

■productiortwli be: sufficiently tow to allow a solids retention time in :the_;existing ae tion^:.tanks thatwill.be.sufficientiylongfor nitrification totake laee. The capaeity ofthe-system is^'inereased, a.s the:systera^: wiH be able to process more wastewater and sludge due.to the primarytreatment;. :pertorm.ed^'by-the otatingvbelt sieve 18 which. esults.inthat the spare capacity^', can. be .used to connect. more population equivalent tothetreatmentlsysterri. The rotating¹ belt ,s^'ieve 18 will also result in thatthe aeratipn.tanks 2i.;and the means 22 for secondary and/or tertiary .biological^'ahd. natural removal treatment will have spare capacity resulting in that trtetotal treatment system will have more capacity,

There;are also considerable economic savings, asthis resui in lower sludge oiunie which needs, to b_.e_.transported away from the system and be further processed. As the operation. and maintenance cost also are reduced (for example power savings for the aeration tanks), the total costs of the system are considerably lower of a system according to the invention. Surplus sludge concentration is considerable increased and surplus sludge volume is considerably reduced. The oxygen demand is considerably reduced and the oxidation ditch MLSS- Eoncentration can be reduced ifthe flow through the means for^:secondary:and/or tertiary biological and natural removal treatment is significantly increased. The WAS.produdtion is considerably reduced: and the primary s!udgeproduetion is considerably Increased

As mentioned in the general part of the description the -system can include means for measuring the influent wastewater and the level of wastewater in an inlet chamber, wherein the rotating belt sieve runs:

Mentioned -in the genera! part is also means for removing sludge from the rotating belt sieve. It is important to notice that when using means like. described Norwegian Patents No. 310182 and 178608, the dew.atering and/o^^{^} is completed- by the::dewatering . unit. The. means for removing ;siudge _;as described in Norwegian. Patents No..3.10182 and.l 7860S, is,also: the first.step of :dewatering and^orthickening, and highly influencing t e; dewatertngi thickening efficiency a ndihe characteFistics-Ofthe.dewatered^nd or thickened :siudge.

The^:systenxis preferably also provided withione .or more sensor meansfor measuring con itions

suspended¾o!ids, waste;activate.d slUdge^return. activate¾:sludg¾ BDD_S con

Thesy_:slem can.al.so.;inelude meansfor ^'-further. dewatering_;and/or thickening of ^wate ed

suitable-dewateringimetho

Theisyitem furtherinefudes cohtrol unit for controlling the: performance of th rdtating:belt^; sieve,. based .on-measuradkonditions.T^ beflo , beit speedi pressureidrop, influept TSS^-effluepi^'TSS, fluid level, etc.

Modifications

As shown in Figure 3, the^system according to the invention can. include^ibfilrh reactors 30, in addition to oxidation dltches;and conventional actiyated.-sluci.ge systems. Ther^wouid'be no RAS, butthe biological ifsurpius) sludge :3i,can goto.¾^

thickening together with primary sludge.

Even though it is described in the .example the use of oxidation ditches!wiihi. surface aerators^K, is obvjbusthat.the oxidattoh . ditches may other means for aeration such asVibptto diffusers or standard propeller mixers to provide a circular flow pattern.

Claims

1. System for treatment. of wastewater -and sludge at municipal or industrial wastewater treatment plants, which system includes one or mo e of: coarse screens {ll):and/orsand and grit-traps (20) for removing objects from jnfluerst wastewater (12); one or more means (22) for secondary and/or tertiary .biological and natural removal treatment or one or more final clarifiers (14) for the separation of wastewater into, return activated sludge (15), waste activated sludge ^;(.16)^,and effluent wastewater;(17);_:and .one or more means (13) or removing organic matter; characterized in that theisystem includes one ormore rotating belt sieves (IS) arranged for simultaneous primary treatment of wastewater and dewatering and/or t ickening of primary and biological (secondary) sludge.

:2. System according to claim 1, characterized irvthat the system. is arranged for nitrification. ;3.:Syste.m accordingito claim ^ characterized in . that the- waste activated sludge^'.(.16}¾ . rovided to the.:i)neor more 'rotating belt sieves .(IS)_*

^?4. System -according to claim 3, characterized: in that the rotating be lt sieves (l8) 1s¾rrariged to dispose dewateied a^d/or ^

.5. System ;according td claim ^ characterized in that the-system includes meahs. such asia -screw press, for farther dew^^

S. System according to e!aim:!, characterized In . that the ./system' in non-mechanicaf means for removing-sludgefrorn the rotating beit sieve..(18).

7: System according to laim 1_/ characterized in that the system is provided with one or more sensor. meartsifor measuririg conditions at . different positions of the system, such as: total suspended solids, waste activated sludge, return activated sludge, 30D₅ concentrations, influent total suspended-solids, effluent tota suspendedsbiids-or fluid level in an inlet chamber.

8. System according to claim 1, characterized in that means (13) for removing organic matter are oxidation d itches or biofilm rea ctors.

9..^'Method for treatmerit .of waste water and sludge at municipal or industrial wastewater treatment plants., by means of a system hich inciudes one or more of: coarse screens (11) and/or sand and;grittraps (20) for removing objectsfrom influent wastewater (12); one or more means (22) for secondary and/or tertiary biologicaLand natural removal treatment (22),or,one or more final . ciarifiers (14) for the separation xif wastewater into return activated sludge: (15), waste activated sludge (16) and effluent wastewater (17); and one or more means (13) for removing organic matter; characterized in that the method includes simultaneous.primary treatment of wastewater and dewatering. and/orthickening of.primary.and biological (secondary) sludge,

10. Method according to claim 9, characterized in that simuitaneous primary treatment of wastewater a nd dewatering and/or thickening of prima ry and biological (secondary) sludge is performed by^;means.:of one or more rotating beltsieves (18).

11. Method according to claims.9-¾ characterized by . roviding waste activated:.sludge.(16):.on the rotating belt sieves (18).

12. ^:Method:accordihgto..claimS'9-ll,.. charaeterizedrin disposingidewatere.d and/or thickened sludge,(19) hy:means of the. rotating belt sieves (18).

13.^■ Method according to. claim

thickening.metho^'ds¾rte

14. Method .according^' to claim 9-10,.characterized~in;^;performing.nitrificatia^ by.; means of the rotating bsfcste^

sufficiently low to altow a solids retention time in the eration tanks (21) to be. sufficiently long for nitrification to take; piace.

15. Method according to claim 9, characterized in measuring conditions at different positions of the system, such as total suspended sojicls^waste activated sludge, return activated sludge,^" BO.D_s concentrations, influent wastewater flow or wastewater level in a inlet: chamber.

16. Methodraccording to any one of claims 9-15, characterized in controlling the rotating, belt sieve (18) :for creating a :f liter mat . on a rotating^elt sieve (18) .to achieve maxima! cleaning efficiency/particle reduction and/or hydraulic capacity.