Henriksdals avloppsreningsverk genomgår en stor ombyggnation för att kunna hantera bådeökad belastning och de strängare reningskrav som förväntas i framtiden. Med anledning attBromma reningsverk kommer läggas ned, kommer ytterligare avloppsvatten ledas tillHenriksdals avloppsreningsverk. Då även en kraftig ökning av befolkningen iupptagningsområdet förväntas behöver reningsverket klara en fördubblad kapacitet jämfört medidag. Dagens reningskrav med avseende på kväve är 10 mg/L och detta förväntas i framtidenskärpas till 6 mg/L. För att uppnå dessa krav kommer den biologiska reningen i den nuvarandeaktivslamprocessen kombineras med membranfiltrering i en så kallad membranbioreaktor(MBR). I den biologiska reningen renas vattnet från kväve i två steg med hjälp av bakterier.Dessa steg är nitrifikation och denitrifikation. På pilotanläggningen vid Hammarby sjöstadsverk har det under året 2018 varit av intresse attstudera förekomsten av kvävefraktioner i reningslinjen, då den första av sju MBRbehandlingslinjerkommer att startas upp vid Henriksdals ARV i början av 2020. Vid uppstartav denna linje finns vissa begränsningar vad gäller dosering av kemikalier för fosfor- ochkväverening. Ingen kolkälla eller fällningskemikalie kommer att kunna doseras, då tankar fördessa ej kommer vara färdigbyggda. För att undersöka hur kvävet agerar i de olika zonerna, och om det är möjligt att uppnå önskadkväverening under dessa förutsättningar, har 12 provpunkter valts ut i den biologiskareningslinjen. Halten av NO2-N, NO3-N, NH4-N, N-tot och COD har uppmätts i dessa punkterunder fyra separata tillfällen. Proverna har analyserats och massbalanser över de olika tankarnai reningslinjen har ställts upp. Resultaten varierar mellan de olika provomgångarna som utförtspå morgon respektive efter lunch, men en del trender kan observeras. Fördenitrifikationen skeri två tankar, varav den andra tanken, BR2, uppvisar mycket låga eller obefintliga förändringar imassflödet av nitrat-kväve (NO3-N) vilket tyder på att endast en tank med fördenitrifikationenskulle vara tillräcklig. Den första tanken för nitrifikation uppvisar också dåliga resultat vilkenkan tyda på att tanken har för låg syrehalt och behöver luftas bättre. Tanken förefterdenitrifikation har fortfarande stora mängder nitratkväve i utflödet, vilket innebär att tvåtankar med efterdenitrifikation skulle kunna ge bättre resultat. Vid alla provtagningstillfällenuppmättes en halt av totalkväve (N-tot) under 10 mg/L i det renade permeatet. Medelvärdet förde fyra tillfällena låg dessutom under det framtida kravet på 6 mg/L. / Henriksdals sewage treatment plant is undergoing a major reconstruction in order to handleincreased load as well as the stricter cleaning requirements expected in the future. Due to theplanned shutdown of Bromma treatment plant, additional wastewater will be led to Henriksdalssewage treatment plant. When a significant increase in population in the catchment area is alsoexpected, the treatment plant will need a doubling of its capacity compared to today. Today'snitrogen treatment requirements in the effluent wastewater are 10 mg/L and this is expected tobe 6 mg/L in future. To achieve these requirements, the biological treatment step of the currentactive sludge process will be combined with membrane filtration in a so-called membranebioreactor (MBR). In the biological treatment, the nitrogen removal is a two-step process usingbacteria. These steps are nitrification and denitrification. In the pilot plant at Hammarby Sjöstadsverk, in 2018, it is of interest to study the presence ofnitrogen fractions in the process, since the first of seven MBR treatment lines will be started atHenriksdals WWTP early 2020. At the start of this line there are some limitations regardingdosage of chemicals for the removal of phosphorus and nitrogen. No carbon source orprecipitation chemicals will be possible to add, since the storage for these will not be constructedin time for the startup. To examine how the nitrogen acts in the different zones, and if it is possible to achieve thedesired nitrogen removal under these conditions, 12 test points have been selected in thebiological process line. The total concentration of nitrogen, N-tot, and the concentration ofnitrogen in the form of NO2, NO3, NH4, as well as the COD have been measured in these pointson four separate occasions. The samples have been analyzed and mass balances over thedifferent zones in the process line have been set up. The results vary between the different tests,performed in the morning and after lunch, but some trends can be observed. The predenitrificationtakes place in two zones, of which the second zone, BR2, exhibits very low ornon-existent changes in the mass flow of nitrate nitrogen (NO3-N), indicating that one zone withpre-denitrification would be sufficient. The first zone of nitrification also shows poor results,which may indicate that the zone has a low oxygen content and needs better airflow. The zonewith after-denitrification still has large amounts of nitrate in the outflow, which means that twozones with post-denitrification could produce better results. At all samplings a total nitrogen (Ntot)content of less than 10 mg/L was measured in the purified permeate flow. The average ofthe four occasions was also below the future requirement of 6 mg/L.

The study aims to investigate an appropriate wastewater treatment process to treat domestic wastewater in Hanoi City which contain low-strength for COD (120-200 mg/L) but high in nitrogen content (10-40 mg/L). A lab scale anoxic-oxic system with a hollow fiber-Membrane Separation Bioreactor was operated at a flow rate of 5-10 L/h over a period of 150 days. The reactor was operated at different sludge recirculation rates. The MBR maintained relatively constant transmembrane pressure. During 150 days of reactor operation, treated water quality have COD of around 20 mg/L, NH4-N of less than 1 mg/L, NO3-N of less than 5 mg/L. The system shows good and stable efficiency for organic matter and nitrogen removal without adding an external carbon source and coagulants. The results based on the study indicated that the proposed process configuration has potential to treat the low-strength wastewater in Hanoi. / Mục tiêu của nghiên cứu là đề xuất được một công nghệ hiệu quả và phù hợp để xử lý nước thải sinh họat ở các đô thị của Việt nam, là loại nước thải được thu gom từ hệ thống thoát nước chung có nồng độ chất hữu cơ thấp (COD 120-200 mg/l) nhưng hàm lượng chất dinh dưỡng như Nitơ, Phốt pho khá cao (T-N: 10-40 mg/L). Chúng tôi đã nghiên cứu và vận hành chạy thử mô hình xử lý sinh học yếm khí - kỵ khí (AO) kết hợp với màng vi lọc ở quy mô mô hình phòng thí nghiệm (công suất 5-10 L/h) ở các chế độ công suất bùn tuần hoàn khác nhau. Kết quả xử lý trong thời gian 5 tháng vận hành mô hình cho thấy chất lượng nước thải sau xử lý có hàm lượng COD nhỏ hơn 20 mg/L, NH4-N nhỏ hơn 1 mg/L, NO3-N nhỏ hơn 5 mg/L. Hiệu suất xử lý chất hữu cơ và chất dinh dưỡng rất ổn định và hệ thống không phải sử dụng các nguồn bổ sung chất hữu cơ hay các hóa chất trợ lắng như các công nghệ đang áp dụng. Kết quả cho thấy công nghệ AO kết hợp màng vi lọc có khả năng áp dụng thực tế, phù hợp với những nơi có quỹ đất nhỏ, chất lượng nước sau xử lý rất cao có thể phục vụ cho mục đích tái sử dụng.

Recently, there has been an increased interest in the production of volatile fatty acids from pulp and paper sludge using an immersed membrane bioreactor during anaerobic digestion. The production of biogas through anaerobic digestion has been a hot topic in recent years, but it is no longer economically viable due to competition from fossil fuels. As a result, the production of volatile fatty acids has been investigated in this study using pulp and paper sludge as substrate. To investigate the effect of methane inhibition on enhanced volatile fatty acid production, various parameters, and pre-treatments such as pH, O2 presence, thermal heat shock, and chemical BES-addition were used. Heat shock pre-treatment produced the most volatile fatty acids (2.4 g/L) while producing the least methane (50 mL/g VS). The immersed membrane bioreactor was successfully used to produce volatile fatty acids for 54 days. / En av dagens problem är den ökade populationen vilket har lett till ökade mängder av avfall från mat och slam. Innan låg ett stort fokus på att använda dessa rester i en anaerobisk rötning för att producera biogas. Dock har detta visat sig att inte vara ekonomiskt hållbart just på grund av att inte kunna konkurrera med fossila bränslen, därför har man i stället fokuserat på att ta fram de intermediära produkterna från rötning processen, dvs flyktiga fettsyror. Detta projekt har fokuserat på att producera flyktiga fettsyror från pappersmassa och papperslam som är potentiellt lättare nedbrytbart, än andra lignocellulosa rika substrat. När man vill maximera flyktiga fettsyraproduktionen, då är det viktigt att samtidigt förhindra produktion av biogas. Effekten av flera olika parametrar, såsom närvaro av syre, pH, för behandling med värmechockeller BES-tillsats, för att inhibera produktion av metan har därför undersökts. Förbehandlingen med värmechock ledde till runt 2,4g/L fettsyraproduktion, tillsammans med den minsta mängden av metan, runt 50 mL/gVS. Membranreaktorn kunde användes framgångsrikt för kontinuerlig produktion av flyktiga fettsyror under 54 dagar.

Membrane BioReactor (MBR) is a wastewater treatment method which combine both biological and physical cleaning. In the membrane tank there is membrane fibres which physically separate wastewater from containing organic material. This causes the membrane fibres to easily build fouling. A measure that can describe membrane fouling, is the pressure across the fiber membranes (transmembrane pressure). The higher the pressure, the dirtier the fiber membranes. Therefore the fiber membranes need to be cleaned frequently. A current applying cleaning method, membrane air scouring, works by releasing air bubbles from the bottom of the tank to remove organic fouling from the membrane fibres. Membrane air scouring accounts for a big part of the total energy consumption. Therefore research is needed to find development opportunities to counteract membrane fouling and to make membrane air scouring more energy efficient. In this master thesis, two different air scouring strategies are used in the membrane tank to reduce the development of the membrane fouling. The first aeration strategy, with lower air supply, was operated at a constant air supply of 5.04 m3air/m3permeate. The second aeration strategy, with higher air supply, varied instead the air supply linearly with increased incoming flow. The different aeration strategies were then compared with each other, and it was looked at which aeration strategy is the most energy efficient regarding energy consumption per permeate volume produced, to reduce membrane fouling.For three weeks, each aeration strategy was applied in the pilot plant at Himmerfjärdsverket. During the strategies, maintenance cleaning was done with oxalic acid, as the commonly used chemical sodium hypochlorite was not available. The transmembrane pressure in the membrane tank was analysed during the aeration strategies to investigate how the membrane fouling developed. The sludge properties of the water in the pilot plant were also analysed, to see if these had any influence on the membrane fouling. Energy calculations were also done to for quantify the energy consumption from the membrane air scouring.The thing that had the biggest impact on energy consumption was the size of the incoming flow. Then irreversible fouling of inorganic substances that clog the membrane pores. Finally, reversible fouling of organic material that forms cakelayers on the fibres. The investigation showed that the aeration strategy with the lowest air supply was enough to successfully suppress the membrane fouling and maintain a high permeability. In pilot-scale, consumed the air strategy with lower air supply 74 Wh/m3, while the higher air supply aeration strategy consumed 92 Wh/m3for the pilot-scale membrane air cleaning. At full scale, the aeration strategy with lower air supply is expected to consume 46 Wh/m3. In full scale, more frequent maintenance cleaning may need to be done, which means poorer filtration performance during washing periods. The recommendation is to test the aeration strategy with lower air supply and at the same time have more frequent maintenance cleaning, to investigate whether it is the most energy efficient option in the long term. / Membrane BioReactor (MBR) är en vattenreningsteknik som tillämpar både biologisk och fysisk vattenrening. I membrantanken finns det membranfibrer som fysiskt separerar avloppsvattnet från det innehållande organiska materialet. Detta får membranfibrerna att lätt bli nedsmutsade. Ett mått som kan beskriva membrannedsmutsningen är trycket över membranfibrerna (transmembrantrycket). Ju smutsigare membranfibrerna är, desto sämre genomsläpplighet får de och trycket som krävs att suga vattnet igenom dem ökar. Membranfibrerna behöver därmed rengöras ofta. I dagsläget görs det med hjälp av luftbubblor som skaver bort smutsen som finns på fibrerna. Att lufta membrantanken kallas membranluftrengöring och står för en stor del av reningsteknikens totala energiförbrukning. För att göra MBR-processen till en mer energieffektiv vattenreningsteknik, behöver kunskapen öka om hur nedsmutsningen av membranen kan motverkas och membranluftrengöringen bli mer effektiv.I detta examensarbete tillämpas två olika strategier för att lufta membrantanken. Den första luftningsstrategin, med en lägre lufttillförsel, drevs med en konstant lufttillförsel på 5,04 m3luft/m3permeat. Den andra luftningsstrategi, med en högre lufttillförsel, varierade istället lufttillförseln linjärt vid ökat inkommande flöde av avloppsvatten. De olika luftningsstrategierna jämfördes sedan med varandra med avseende på vilken luftningsstrategi som är mest energieffektiv med avseende på energiförbrukning per producerad permeatvolym.I tre veckor tillämpades varsin luftningsstrategi i pilotanläggningen på Himmerfjärdsverket. Under tiden utfördes det underhållsrengöring, dock med oxalsyra, eftersom den vanligtvis använda kemikalien natriumhypoklorit inte var tillgänglig. Transmembrantrycket i membrantanken analyserades under luftningsstrategierna för att utreda hur membrannedsmutsningen utvecklat sig. Slamegenskaperna för vattnet i pilotanläggningen analyserades också, för att se om dessa hade någon påverkan på membrannedsmutsningen. Det gjordes därefter energiberäkningar för att ta reda på membranluftrengöringens energiförbrukning.Det som hade störst påverkan på energiförbrukningen visade sig vara storleken pådet inkommande flödet. Därefter irreversibel nedsmutsning som igensätter membranporerna. Sist kom reversibel nedsmutsning av organiskt material som bildar beläggningar på fibrerna. Utredningen visade att luftningsstrategin med lägst lufttillförsel var tillräcklig för att lyckas dämpa membrannedsmutsningen och bibehålla en hög genomsläpplighet. I pilotanläggningen förbrukade luftningsstrategin med lägre lufttillförsel 74 Wh/m3, medan luftningsstrategin med högre lufttillförsel förbrukade 92 Wh/m3. I fullskala förväntas luftningsstrategin med lägre lufttillförsel förbruka 46 Wh/m3. I fullskala kan mer frekvent underhållsrengöring behöva göras, vilket innebär sämre filtreringsprestanda under tvättperioderna. Rekommendationen är att testa luftningsstrategin med lägre lufttillförsel och samtidigt ha mer frekvent underhållsrengöring, för att utreda om det är det mest energieffektiva alternativet på lång sikt.

A conventional membrane bioreactor (MBR) and two moving bed bioreactors coupled with ultrafiltration membrane filtration were operated for close to six months to investigate biological nutrient removal and potential fouling inducing parameter mitigation. Unique to one of the moving bed membrane bioreactors (MBMBR) was a newly designed media that incorporated a hydrodynamic exterior carrier with a highly porous interior packing. Preliminary investigation indicates that nitrogen compounds were superiorly removed in the two MBMBRs when compared with the MBR. This is a result of denitrification processes occurring in anoxic micro-zones found within the depths of the biofilm affixed to media. Fouling propensity was found to be increased by over four times in the MBMBR systems as compared to the MBR. Mixed liquor, permeate and filtrate analysis, membrane fibre examination and permeability tests indicated that colloidal organic carbon, as well as soluble microbial products were the dominant fouling inducing compounds. / Manuscript format / The Natural Sciences and Engineering Research Council of Canada

Objectives of this master's thesis are to process review of technologies used to treat wastewater in alpine environment in Slovakia and in foreign countries. Thesis also includes mapping of situation of chosen alpine cottages in High Tatras. For cottages with unsuitable technology will be suggested more suitable solution.

<p>In the pilot plant at Hammarby Sjöstad, Sjöstadsverket, several new methods are tested in order to achieve a good use of resources. When a new technique is considered it is often the performance of the technique itself, under given conditions, that is evaluated. However, in order to evaluate the overall function the whole picture is needed. With a system analysis it becomes possible to make a comparison where all the positive aspects are put up against the negative ones, for the technique itself as well as its requirements. In this way the influence that minor components have on an entire system can be considered.</p><p>This report presents a system analysis of an anaerobic membrane reactor (MBR) with a VSEP-membrane (Vibratory Shear Enhanced Process). The MBR is tested at the research treatment plant at Hammarby Sjöstad. In the analysis presented two different treatment techniques treating two different types of wastewaters are compared. The considered techniques are conventional (represented by an active sludge process) and the MBRtechnique. The waters treated are a mixed wastewater and wastewater from a separating system where closet water is separated from greywater and mixed with food waste from waste disposers.</p><p>The system analysis has been carried out with the URWARE (URban WAter REsearch) system analysis tool. A new URWARE-model that describes the anaerobic reactor and the VSEP membrane was created in order to generate the system structures needed for the analysis. The model consists of two submodels, which as the other URWARE-models are mass-flow, steady-state models based on yearly average-values. The model was tested and calibrated from the test-results at the Hammarby Sjöstad pilot plant. In the study the systems are compared considering energy, exergy and recirculation of nutrients.</p><p>The VSEP-technique has some advantages compared to the conventional system as it ensures that a large part of the nutritional content in the wastewater can be retained. The advantage is more obvious with the separated system, where food waste is mixed with closet water. Also the global warming potential of the new technique is lower. However, conventional treatment is better from an exergy-perspective. This is mostly due to the high energy consumption as a result of the reversed osmosis (RO) required for post treatment.</p> / <p>I försöksanläggningen vid Hammarby Sjöstad, Sjöstadsverket undersöks flera olika metoder för att uppnå största möjliga resursutnyttjande. När en ny teknik utprovas är det i allmänhet funktionen hos den givna metoden under givna förutsättningar som undersöks. För att få ett helhetsperspektiv krävs emellertid att den sätts in i sitt sammanhang. En systemanalys gör det möjligt att få en bild av alla för- och nackdelar, såväl av tekniken i sig som av de förutsättningar den kräver. Även effekter som små delar har på ett helt system kan då belysas och dess betydelse för helheten fastställas.</p><p>Föreliggande studie möjliggör en systemanalytisk utvärdering av en anaerob membranbioreaktor (MBR) kopplad till ett VSEP-membran (Vibratory Shear Enhanced Process) som är under utprovning vid Sjöstadsverket. Studien jämför två vattenreningstekniker för behandling av två olika typer av avloppsvatten. Dels rör det sig om konventionell teknik (aktiv slam-rening liknande den behandlingsmetod som används idag), dels den nya MBRtekniken. De vatten som behandlas är blandat avloppsvatten respektive sorterat klosettvatten blandat med matavfall från avfallskvarnar.</p><p>Systemanalysen har utförts med hjälp av systemanalysverktyget URWARE (URban WAter REsearch). För att kunna bygga upp önskade systemstrukturer har en ny modell för att beskriva den anaeroba reaktorn och VSEP-membranet skapats inom ramen för detta examensarbete. Modellen består av två delmodeller, som liksom övriga modeller i URWARE är substansflödesmodeller där beräkningar är baserade på årsmedelvärden. Modellen har utprovats och kalibrerats mot mätresultat från pilotförsöken vid Sjöstadsverket. I studien jämförs systemen med avseende på energi, exergi och återföring av närsalter.</p><p>Utifrån systemanalysen konstateras att MBR-tekniken ger vissa fördelar gentemot konventionell teknik då en stor del av näringsinnehållet från avloppsvattnet kan fångas upp. Detta gäller speciellt då tekniken används i kombination med ett separerat avloppssystem där matavfall blandas med klosettvatten. Även växthuspotential för den nya tekniken är lägre totalt sett. Ur exergisynpunkt är konventionell teknik emellertid mer fördelaktig. Till stor del beror detta på hög energiförbrukning pga. den efterbehandling med omvänd osmos (RO) som systemet i dess nuvarande utformning kräver.</p>

In the pilot plant at Hammarby Sjöstad, Sjöstadsverket, several new methods are tested in order to achieve a good use of resources. When a new technique is considered it is often the performance of the technique itself, under given conditions, that is evaluated. However, in order to evaluate the overall function the whole picture is needed. With a system analysis it becomes possible to make a comparison where all the positive aspects are put up against the negative ones, for the technique itself as well as its requirements. In this way the influence that minor components have on an entire system can be considered. This report presents a system analysis of an anaerobic membrane reactor (MBR) with a VSEP-membrane (Vibratory Shear Enhanced Process). The MBR is tested at the research treatment plant at Hammarby Sjöstad. In the analysis presented two different treatment techniques treating two different types of wastewaters are compared. The considered techniques are conventional (represented by an active sludge process) and the MBRtechnique. The waters treated are a mixed wastewater and wastewater from a separating system where closet water is separated from greywater and mixed with food waste from waste disposers. The system analysis has been carried out with the URWARE (URban WAter REsearch) system analysis tool. A new URWARE-model that describes the anaerobic reactor and the VSEP membrane was created in order to generate the system structures needed for the analysis. The model consists of two submodels, which as the other URWARE-models are mass-flow, steady-state models based on yearly average-values. The model was tested and calibrated from the test-results at the Hammarby Sjöstad pilot plant. In the study the systems are compared considering energy, exergy and recirculation of nutrients. The VSEP-technique has some advantages compared to the conventional system as it ensures that a large part of the nutritional content in the wastewater can be retained. The advantage is more obvious with the separated system, where food waste is mixed with closet water. Also the global warming potential of the new technique is lower. However, conventional treatment is better from an exergy-perspective. This is mostly due to the high energy consumption as a result of the reversed osmosis (RO) required for post treatment. / I försöksanläggningen vid Hammarby Sjöstad, Sjöstadsverket undersöks flera olika metoder för att uppnå största möjliga resursutnyttjande. När en ny teknik utprovas är det i allmänhet funktionen hos den givna metoden under givna förutsättningar som undersöks. För att få ett helhetsperspektiv krävs emellertid att den sätts in i sitt sammanhang. En systemanalys gör det möjligt att få en bild av alla för- och nackdelar, såväl av tekniken i sig som av de förutsättningar den kräver. Även effekter som små delar har på ett helt system kan då belysas och dess betydelse för helheten fastställas. Föreliggande studie möjliggör en systemanalytisk utvärdering av en anaerob membranbioreaktor (MBR) kopplad till ett VSEP-membran (Vibratory Shear Enhanced Process) som är under utprovning vid Sjöstadsverket. Studien jämför två vattenreningstekniker för behandling av två olika typer av avloppsvatten. Dels rör det sig om konventionell teknik (aktiv slam-rening liknande den behandlingsmetod som används idag), dels den nya MBRtekniken. De vatten som behandlas är blandat avloppsvatten respektive sorterat klosettvatten blandat med matavfall från avfallskvarnar. Systemanalysen har utförts med hjälp av systemanalysverktyget URWARE (URban WAter REsearch). För att kunna bygga upp önskade systemstrukturer har en ny modell för att beskriva den anaeroba reaktorn och VSEP-membranet skapats inom ramen för detta examensarbete. Modellen består av två delmodeller, som liksom övriga modeller i URWARE är substansflödesmodeller där beräkningar är baserade på årsmedelvärden. Modellen har utprovats och kalibrerats mot mätresultat från pilotförsöken vid Sjöstadsverket. I studien jämförs systemen med avseende på energi, exergi och återföring av närsalter. Utifrån systemanalysen konstateras att MBR-tekniken ger vissa fördelar gentemot konventionell teknik då en stor del av näringsinnehållet från avloppsvattnet kan fångas upp. Detta gäller speciellt då tekniken används i kombination med ett separerat avloppssystem där matavfall blandas med klosettvatten. Även växthuspotential för den nya tekniken är lägre totalt sett. Ur exergisynpunkt är konventionell teknik emellertid mer fördelaktig. Till stor del beror detta på hög energiförbrukning pga. den efterbehandling med omvänd osmos (RO) som systemet i dess nuvarande utformning kräver.

The combination of moving bed biofilm reactors and membrane bioreactors (MBBR-MR) can compensate for the drawbacks of both of these systems and further increase their acceptance and application in wastewater treatment industries. Despite the potential benefits of a MBBR-MR technology there has only been limited study of this configuration. The present study consisted of an overall assessment of the performance of a combined MBBR-MR system under high and low loading rates. Since colloidal matter in mixed liquor suspended solid (MLSS) is considered as one of the important contributors to membrane fouling, pre-treatment of membrane feed by coagulation was investigated for improving membrane performance. The performance of the MBBR-MR was assessed based on its chemical oxygen demand (COD) removal efficiency and membrane fouling mechanisms. The study was carried out using pilot-scale MBBR and bench-scale batch membrane filtration setups (Millipore Inc. Bedford, MA). The pilot MBBR had a working volume of 1.8 m3 and a 30% carrier fill fraction. The MBBR was operated with loading rates of 160 ± 44 g/m2/d (hydraulic residence time (HRT) of 4.6 h) and 223 g/m2/d (HRT of 2.6 h). The MBBR feed was obtained from a starch recovery line in a potato chip processing factory. The carriers were mixed by coarse bubble aeration and the dissolved oxygen (DO) was maintained above 2 mg/l. Preliminary jar test trials (based on turbidity removal) were performed in order to obtain an optimal dosage of coagulants for subsequent ultrafiltration (UF) tests. The efficiency of three coagulants (alum, ferric chloride and a blend of polyaluminum chloride and polyamine) was evaluated. The membranes were composed of polyethersulfone (PES) and had a pore size of 0.05 microns. The results of this study indicate that the combination of MBBR with membrane filtration can be operated at relatively high loading rates to yield a constant high quality permeate that is suitable for water reuse purposes. Fouling of the membrane by the wastewater was found to be substantially reduced by treatment with the MBBR. The reversible and irreversible fouling of the MBBR effluent were 56 and 63%, respectively, of that observed with the raw wastewater. The MBBR Loading-rate was found to affect treatment efficiency of the MBBR-MR and membrane performance. Operation under the elevated loading-rate conditions HRT = 2.6 hours) resulted in an increase in the irreversible fouling of the membranes (60% on average). The addition of all the coagulants in this study was found to decrease the fouling of the membrane. However, the extent of the pre-coagulation effect on membrane fouling was found to strongly depend on the type and dosage of the coagulant and the MBBR effluent characteristics. All the coagulants were effective in decreasing membrane fouling at their optimal dosages which was determined in preliminary jar tests. Ferric chloride performed the best as a pretreatment coagulant compared to alum (Aluminum sulfate) and the coagulant blend with reductions in both reversible and irreversible fouling (43-86% and 51-71%, respectively) and increased consistency (in decreasing fouling) as compared to the other coagulants. Alum had no effect on irreversible fouling and the coagulant blend significantly increased irreversible fouling in some trials (up to 196% or by a factor of 3 when overdosed). Additionally, alum and the blend were, on average, 29% and 7%, less effective than ferric chloride in reducing reversible fouling under the conditions and dosages tested.

The combination of moving bed biofilm reactors and membrane bioreactors (MBBR-MR) can compensate for the drawbacks of both of these systems and further increase their acceptance and application in wastewater treatment industries. Despite the potential benefits of a MBBR-MR technology there has only been limited study of this configuration. The present study consisted of an overall assessment of the performance of a combined MBBR-MR system under high and low loading rates. Since colloidal matter in mixed liquor suspended solid (MLSS) is considered as one of the important contributors to membrane fouling, pre-treatment of membrane feed by coagulation was investigated for improving membrane performance. The performance of the MBBR-MR was assessed based on its chemical oxygen demand (COD) removal efficiency and membrane fouling mechanisms. The study was carried out using pilot-scale MBBR and bench-scale batch membrane filtration setups (Millipore Inc. Bedford, MA). The pilot MBBR had a working volume of 1.8 m3 and a 30% carrier fill fraction. The MBBR was operated with loading rates of 160 ± 44 g/m2/d (hydraulic residence time (HRT) of 4.6 h) and 223 g/m2/d (HRT of 2.6 h). The MBBR feed was obtained from a starch recovery line in a potato chip processing factory. The carriers were mixed by coarse bubble aeration and the dissolved oxygen (DO) was maintained above 2 mg/l. Preliminary jar test trials (based on turbidity removal) were performed in order to obtain an optimal dosage of coagulants for subsequent ultrafiltration (UF) tests. The efficiency of three coagulants (alum, ferric chloride and a blend of polyaluminum chloride and polyamine) was evaluated. The membranes were composed of polyethersulfone (PES) and had a pore size of 0.05 microns. The results of this study indicate that the combination of MBBR with membrane filtration can be operated at relatively high loading rates to yield a constant high quality permeate that is suitable for water reuse purposes. Fouling of the membrane by the wastewater was found to be substantially reduced by treatment with the MBBR. The reversible and irreversible fouling of the MBBR effluent were 56 and 63%, respectively, of that observed with the raw wastewater. The MBBR Loading-rate was found to affect treatment efficiency of the MBBR-MR and membrane performance. Operation under the elevated loading-rate conditions HRT = 2.6 hours) resulted in an increase in the irreversible fouling of the membranes (60% on average). The addition of all the coagulants in this study was found to decrease the fouling of the membrane. However, the extent of the pre-coagulation effect on membrane fouling was found to strongly depend on the type and dosage of the coagulant and the MBBR effluent characteristics. All the coagulants were effective in decreasing membrane fouling at their optimal dosages which was determined in preliminary jar tests. Ferric chloride performed the best as a pretreatment coagulant compared to alum (Aluminum sulfate) and the coagulant blend with reductions in both reversible and irreversible fouling (43-86% and 51-71%, respectively) and increased consistency (in decreasing fouling) as compared to the other coagulants. Alum had no effect on irreversible fouling and the coagulant blend significantly increased irreversible fouling in some trials (up to 196% or by a factor of 3 when overdosed). Additionally, alum and the blend were, on average, 29% and 7%, less effective than ferric chloride in reducing reversible fouling under the conditions and dosages tested.