Under 90-talet uppdagades övergödningsproblematiken i Östersjön, varför omgivande länder enades gällande åtgärder för att minska problemen. De svenska reningsverk som genom sina utsläpp av kväve och fosfor påverkade Östersjön tvingades då införa gränsvärden för kväve- och fosforutsläppen. Vid Arboga reningsverk, vars recipient är Arbogaån som mynnar i Galten, Mälaren, har kvävereducering sedan en tid tillbaka varit i drift. Dock krävdes från och med år 2012 att totalkvävehalten i utgående avloppsvatten ej översteg 15 mg tot-N/l. Införandet av detta gränsvärde resulterade i åtgärder för att minska kväveutsläppen.Rejektvattenbehandling är en vanlig metod för att minska halterna totalkväve i utgående avloppsvatten. Normalt utgör rejektvattnet 0,5–1,0 % av totala inflödet till reningsverket men 10–20 % av inkommande totalkvävebelastningen. I Arboga resulterade det nya gränsvärdet för totalkväveutsläpp i en nybyggnation av en rejektvattenbehandling utformad med fördenitrifikation. Detta innebär att rejektvattnet pumpas genom fyra zoner, två anaeroba följt av två aeroba. Ammoniumkvävet i inkommande vatten omvandlas genom detta processupplägg via nitrat till kvävgas.Denna studie syftade till att kartlägga rejektvattenbehandlingens effekt på halterna av totalkväve i utgående avloppsvatten från Arboga reningsverk. Detta inkluderade både simuleringar i Benchmark Simulation Model no. 2 (BSM2) samt studier genom vattenprovtagning vid Arboga reningsverk. Vid simuleringarna genomförda i BSM2 påvisades en märkbart lägre halt totalkväve i utgående avloppsvatten efter rejektvattenbehandlingens införande. Även vid den provtagningscykel som genomfördes på Arboga reningsverk under april år 2012 påvisades att markanta förändringar skett i utgående halter totalkväve och ammoniumkväve. Halterna totalkväve och ammoniumkväve i utgående avloppsvatten sjönk med ca 40 % respektive 65 % relativt samma tidsperiod år 2008–2011. Detta är dock endast resultat från det initiala skedet av rejektvattenbehandlingen som togs i drift 16 februari år 2012. Studien visade sammanfattningsvis att denna typ av processlösning för rejektvattenbehandling ledde till lägre halter av totalkväve och ammoniumkväve i utgående vatten från Arboga reningsverk. Dock krävs vidare studier för att kartläggaden slutgiltiga effekten av rejektvattenbehandlingen, då den i nuläget ännu ej nått sin slutgiltiga kapacitet. / Eutrophication problems were discovered in the Baltic Sea during the 1990s, why thesurrounding countries came to an agreement regarding measures to reduce the problem. Swedish wastewater treatment plants that influence the Baltic Sea by their emissions ofnitrogen and phosphorus have since introduced limit values for nitrogen and phosphorusconcentrations in the effluent water.At Arboga wastewater treatment plant (WWTP) a nitrogen reduction process withactive sludge was implemented a few years back. The recipient Arbogaån leading intoGalten, Mälaren, has eutrophication issues, and from the year 2012 the concentration oftotal nitrogen in treated wastewater must not exceed 15 mg tot-N/l. This limit resulted inmeasures to reduce nitrogen emissions.Reject water treatment is a common method to reduce the levels of total nitrogen intreated wastewater. Normally, the reject water contributes to 0.5–1.0 % of the totalinflow to the treatment plant but 10–20 % of the incoming total nitrogen load. In Arboga, the new limit for total nitrogen emissions resulted in a reject water treatmentfacility with predenitrification. The reject water is routed through four zones, twoanaerobic followed by two aerobic. Ammonium is by this process converted in to nitrogen gas via nitrate. This study aimed at identifying the effect from what implementing a reject watertreatment on the levels of total nitrogen in treated wastewater from Arboga WWTP.This included simulations in the Benchmark Simulation Model no. 2 (BSM2) as well aswater sampling at Arboga WWTP. The simulations that were carried out in BSM2 showed a significantly lower content of total nitrogen in treated wastewater after thereject water treatment was implemented. The sampling cycle conducted at ArbogaWWTP in April 2012 revealed that changes occurred in the levels of total nitrogen andammonium in the effluent water. The concentrations of total nitrogen and ammonia nitrogen in treated wastewater decreased by about 40 % and 65 %, compared to thesame time period in 2008–2011. This is, however, only results from the initial stage ofthe reject water treatment, which began operating on February 16th 2012.In summary, this study showed that this type of process solution for reject watertreatment resulted in lower levels of total nitrogen and ammonia in the effluent water at  Arboga WWTP. Further studies are needed to determine the final efficiency of the rejectwater treatment, since it yet has to reach its full capacity.

Microalgae are a diverse group of unicellular microorganisms found in various environments, ranging from small garden ponds to lakes with extreme salinity. Common for all microalgae is their ability to convert solar energy and carbon dioxide into chemical energy via photosynthesis. Additionally, they are capable of assimilating large amounts of nitrogen and phosphorus to produce proteins and lipids. These abilities have made microalgae an interesting candidate for next generation wastewater treatment coupled with production of biogas, a renewable energy source in advancement. At the Nykvarn wastewater treatment plant in Linköping, Sweden, 15,400,000 m3 of wastewater are treated annually to remove nitrogen and phosphorus that otherwise would risk to cause eutrophication in surrounding lakes and rivers. Moreover, the treatment plant manages large amounts of sewage sludge that is anaerobically digested to produce biogas and simultaneously reduce the sludge volumes. At the Nykvarn wastewater treatment plant, dewatering of the digested sludge results in a sludge fraction of about 30 % dry content and reject water, which is very nutrient-rich and therefore requires treatment in a SHARON process before it is reintroduced to the main stream of the wastewater treatment plant. In this thesis, the potential of microalgae for nutrient assimilation was studied by monitoring the nutrient removal efficiency of a mixed culture of microalgae when fed with 1) 100 % incoming wastewater, 2) 80 % incoming wastewater + 20 % reject water and 3) 60 % incoming wastewater + 40 % reject water. Furthermore, the effect of a process additive on the nutrient removal efficiency was evaluated. The results showed that microalgae are capable of removing 100 % of ingoing ammonium nitrogen and phosphate phosphorus when fed with incoming wastewater. At transition to 20 % and 40 % reject water, the culture was light-limited with a resulting ammonium reduction of 60 % and a phosphate reduction of around 30 %. The process additive slightly improved the ammonium reduction, however, mainly by formation of nitrite and nitrate by nitrifying bacteria. Moreover, a bio-methane potential test compared the methane potential of the microalgal biomass and the biomass from the SHARON process. The test resulted in an accumulated methane production around 70 mL g-1 VS-1 for the microalgal biomass and 35 mL g-1 VS-1 for the biomass from the SHARON process. That is, the mixed microalgal culture used in this experiment has a methane potential twice that of the biomass from the SHARON process. Finally, an economic analysis of a microalgae based process for purification of reject water showed that the operating costs exceed those of the SHARON process due to high energy consumption. It is thus necessary to choose a cultivation system that effectively utilize the solar energy, as well as maximize the biogas yield from anaerobic digestion of microalgal biomass.

Ett av riksdagens miljömål är att minska övergödande faktorer. En källa till övergödning är kväveutsläpp från avloppsreningsverk. Arvidstorps avloppsreningsverk i Trollhättan väntar en ökad inkommande belastning på grund av befolkningsökning i området samt skarpare krav på utgående halt utsläppt kväve. Detta innebär att planer på att bygga en ny anläggning har satts i verket för att kunna hantera den ökande belastningen. Eventuellt kommer den nya anläggningen inte bli klar innan de nya kraven kommer. Detta gör att reningsverket utreder andra alternativ för att reducera kväve ur avloppsvattnet som kan tas i drift innan den nya anläggningen är klar. Ett alternativ till kväverening är att använda rejektvattenrening eftersom denna avloppsström innehåller höga koncentrationer kväve. Ett annat problem som reningsverket står inför är att kostnaderna för att hantera det avvattnade slammet förväntas öka. Reningsverket utreder därför alternativ för att minska slamvolymen. En biokolsanläggning där biokol tillverkas av det avvattnade slammet skulle kunna vara ett alternativ. Fördelen är att slamvolymen minskar samt att biokol kan användas som vattenrening då det har förmågan att adsorbera ämnen. I detta arbete har två olika tekniker för att rena kväve ur rejektströmmen på Arvidstorps reningsverk studerats. Dessa är dels en beprövad teknik som kallas deammonifikation där kväve renas med bakterier, och dels biokolsadsorption som kvävereningsmetod vilket inte är en lika etablerad reningsteknik på kommunala reningsverk. Deammonifikationsprocessen finns som flera olika tekniker där den som valts för detta arbete är ANITA Mox. ANITA Mox finns som två tillämpningar där den ena är MBBR (Moving Bed Biofilm Reactor) och den andra är IFAS (Integrated Fixed Film Activate Sludge). Målet med detta arbete var att göra en investeingskalkylering för att bedöma hur ekonomiskt försvarbart det är att installera ANITA Mox MBBR eller ANITA Mox IFAS samt uppskatta kvävereningskapaciteten för alternativet med biokolsadsorption. Inga ekonomiska aspekter togs hänsyn till för det senare alternativet.  För beräkningarna byggdes modeller i Excel och två olika experiment utfördes. Pyrolysering av rötrest till biokol och adsorption, samt ett luftningsförsök för att bestämma faktorer som krävs vid beräkning av luftbehov för deammonifikationsprocessen. ANITA Mox MBBR ha de lägsta årskostnaderna, trots att IFAS kan reducera mer kväve och därmed har lägre driftkostnader. IFAS kräver dessutom en mindre volym total sett med reaktor och sedimenteringsbassäng inräknat, men anledningen till den högre kostnaden är de extra instrument och komponenter som krävs till sedimenteringsbassängen med slamretur och den kortare livslängden på dessa komponenter som ger den högre årskostnaden. Biokol som reningsmetod är inte en lämplig metod då det krävs 66 gånger mer rötrest för att producera den mängd biokol som krävs för att rena rejektvattnet. Den rötrest som kommer produceras i en framtida anläggning kan endast reducera 1,5 % av kvävemängden. / One of the environmental goals for the Swedish parliament is to reduce eutrophic factors. A source of eutrophication is nitrogen emissions from waste water treatment plants. Arvidstorp's waste water treatment plant in Trollhättan expects a population increase and sharper requirements for outgoing nitrogen emissions. This means that plans to build a new plant have been put into operation in order to handle the increasing load. The new facility may not be ready before the new requirements come. The waste water treatment plant is therefore investigating other options for reducing nitrogen from the wastewater. An alternative to nitrogen removal is to use reject water purification since this sewage stream contains high concentrations of nitrogen. Another problem facing the waste water treatment plant is that the costs of handling the dewatered sludge is expected to increase. The treatment plant is therefore looking for alternatives to reduce the sludge volume. A biomass pyrolysis plant where biochar is produced by the dewatered sludge could be an alternative since the advantage is that the sludge volume is reduced and that biochar can be used as water purification as it has the ability to adsorb substances. In this work, two different techniques to remove nitrogen from the reject stream at Arvidstorp's treatment plant has been studied. One is a proven technique called deammonification where nitrogen is purified with bacteria, the other one is biochar adsorption as a nitrogen removal process, however not an equally established purification technique on municipal waste water treatment plants. Several different techniques exists as deammonification processes. The one chosen for this work is ANITA Mox. ANITA Mox is available as two implementations where one is MBBR and the other is IFAS. The goals of this work was to make an investment calculation to assess how economically justifiable it is to install either ANITA Mox MBBR or ANITA Mox IFAS and to estimate the nitrogen removal capacity of the alternative with biochar adsorption. No economic aspects were taken into account for the latter option. For the calculations, models were built in Excel and two different experiments were performed. Pyrolysis of digestion residue for biochar production and adsorption, as well as an aeration test to determine the factors required when calculating the air demand for the deammonification process. ANITA Mox MBBR has the lowest annual costs, even though IFAS can reduce more nitrogen and thus have a greater impact on operating costs. IFAS also requires a smaller reactor volume. The reasons for the higher cost are the extra instruments required for the sedimentation basin and the shorter life span of these components which gives the higher annual cost. Biochar as a purification method is not a suitable method as it requires 66 times more sludge to produce the amount of biochar required to purify the reject water. The sludge that will be produced in a future plant can only reduce 1.5% of the nitrogen load.

The legal requirements for wastewater discharge into environment, especially to zones exposed to eutrophication, lately became stricter. Nowadays wastewater treatment plants have to manage with the new rules and assure better biogenic elements’ removal, in comparison with the past. There are some well-known methods of diminishing concentrations of these compounds, but they are ineffective in case of nitrogen-rich streams, as landfill leachate or reject waters from dewatering of digested sludge. This wastewater disturbs conventional processes of nitrification-denitrification and raise necessity of building bigger tanks. The partial nitritation followed by Anaerobic Ammonium Oxidation (Anammox) process appear to be an excellent alternative for traditional nitrification/denitrification. The process was investigated in three different reactors – Membrane Bioreactor (MBR), Moving Bed Biofilm Reactor (MBBR) and Rotating Biological Contactor (RBC). The process was evaluated in two options: as a two-stage process performed in two separate reactors and as a one-stage process. The two-step process, in spite of very low nitrogen removal rates, assured very high nitrogen removal efficiency, exceeding even 90% in case of the MBBR. However, obtained results revealed that the one-step system is a better option than the two-step system, no matter, what kind of nitrogen-rich stream is taken into consideration. Moreover, the one-step process was much less complicated in operation. Performed research confirmed a hypothesis, that the oxygen concentration in the bulk liquid and the nitrite production rate are the limiting factors for the Anammox reaction in a single reactor. In order to make a quick and simple determination of bacteria activity, the Oxygen Uptake Rate (OUR) tests were shown as an excellent tool for evaluation of the current bacteria activity reliably, and without a need of using expensive reagents. It was also shown, that partial nitritation/Anammox process, could be successfully applied at temperatures much lower than the optimum value. Performed Fluorescent in situ Hybridization (FISH) analyses, proved that the Anammox bacteria were mainly responsible for the nitrogen removal process. / QC 20100707

Resurseffektiv kvävereduktion genom nitritation Problematiken med övergödning i våra akvatiska system har lett till hårdare krav på kväverening vid våra reningsverk. En rejektvattenbehandling har visat sig vara ett bra alternativ för att utöka kvävereningen. Vid Nykvarnsverket i Linköping renas avloppsvatten och sedan 2009 finns en SHARON-anläggning i drift. SHARON står för ”Stable High rate Ammonia Removal Over Nitrite” och är en kvävereningsprocess för rejektvatten utvecklad av Grontmij i samarbete med Tekniska universitetet i Delft. I denna studie har SHARON-processen i Linköping undersökts. Dess funktion har utvärderats, drift- och underhållsbehov har studerats och nyckeltal för processen har tagits fram. Arbetet har utförts under våren 2012 genom teoretiska studier samt genom platsbesök och praktiska undersökningar vid Nykvarnsverket i Linköping. Resultaten av denna studie visar att SHARON-processen i Linköping renar ammonium med en reningsgrad på 92,5 %. Denna kväverening motsvarar 18 % av reningsverkets totala kvävereduktion trots att endast cirka 0,5 % av det totala flödet genom reningsverket behandlas. Kostnaden för den utökade kvävereningen är 9,3 kr/kg N och energiåtgången är 2,2 kWh/kg N. Processen har sedan idrifttagandet haft undermålig luftningskapacitet. Detta har troligen lett till den instabilitet som processen uppvisat och att den uppsatta reningsgraden på 97 % inte nås. På grund av låga syrehalter finns Anammoxbakterier i SHARON-reaktorn. Anammoxbakterierna påverkar kvävereningen, men i vilken utsträckning detta sker är inte klarlagt. En ny blåsmaskin är i drift sedan den 30 april och luftningskapaciteten motsvarar nu ursprunglig processdesign. Effekten av den utökade luftningen behöver utvärderas ytterligare. De stöddoseringar av bland annat fosfor och koppar, som är nödvändiga för mikroorganismernas tillväxt, kan exempelvis behöva justeras då processen reagerat på den utökade syretillförseln. / Resource-efficient nitrogen removal through nitritation Eutrophication in our aquatic systems has led to stricter limits regarding nitrogen removal at our wastewater treatment plants. Side stream treatment of reject water has proven to be a good alternative for extended nitrogen removal. At Nykvarnsverket, in Linköping municipality, in Sweden a SHARON-process has been operational since 2009. SHARON stands for ”Stable High rate Ammonia Removal Over Nitrite” and is a nitrogen removal reject water treatment process developed by Grontmij and Delft University of Technology. In this study the function of the SHARON-process in Linköping has been evaluated. The operating and maintenance costs have been calculated. The study has been performed during the spring of 2012 through theoretical studies and practical investigations at Nykvarnsverket in Linköping. The results show that the SHARON-process in Linköping removes ammonia with an efficiency of 92.5 %. This nitrogen removal corresponds to 18 % of the total nitrogen removal at Nykvarnsverket, in spite of the fact that the reject water treatment constitutes only 0.5 % of the treatment plant’s total hydraulic capacity. The cost of the extended nitrogen removal was 9.3 SEK/kg N and the energy consumption was 2.2 kWh/kg N. Ever since the process was put into operation, there has been a lack of aeration capacity. This is probably the cause of the process instability and the fact that the nitrogen removal efficiency does not reach the design value of 97 %. Because of the low levels of dissolved oxygen there are Anammox-bacteria present in the process. The Anammox-bacteria affect the nitrogen removal, but exactly to what extent has not been determined. A new blower is in operation since the 30th of April and the aeration capacity now corresponds to the original design. The effect of the increased aeration needs further evaluation. The aid dosages of copper and phosphorous, important for the growth of the microorganisms, may need to be fine-tuned when the process has reacted to the increased oxygen supply.

The aim of this study was to evaluate the performance of the integrated fixed-film activated sludge (IFAS) reactor achieving partial nitritation/anammox process to treat reject water after dewatering of digested sludge. During the study period, dissolved oxygen setpoint, aeration mode and inflow loading were changed to evaluate their influence on the process performance and efficiency in the reactor. Four different values for dissolved oxygen setpoint were tested: 2.0 mg/L, 1.8 mg/L, 1.5mg/L and 1.3 mg/L. Three different aeration modes in a one-hour cycle were tested: 30 min, 35 min, 40 min. And two different inflow loadings were tested: 2 g N/m2∙d and 1.6 g N/m2∙d. Discussion and evaluation were based on laboratory analyses and online sensors. The highest achieved total inorganic nitrogen removal efficiency was 85.6%, at 40 min aeration per hour, 2.0 mg/L dissolved oxygen and with 2 g N/m2∙day inflow NH4-N loading. Specific anammox activity (SAA) tests were also done for the anaerobic ammonia oxidizing bacteria in biofilm attached to the carriers in the IFAS reactor, and the results showed that the bacteria could achieve a higher nitrogen removal rate than in the pilot-scale IFAS reactor.

No description available.

Vid Hammarby Sjöstadsverk drivs en pilotanläggning som är en mindre skala av det framtida avloppsreningsverket i Henriksdal. Delar av reningsprocessen består av membranbioreaktorer. I pilotanläggningen finns en zon kallad RAS-DeOx dit returslammet från membrantankarna och rejektvattnet från slambehandlingen leds. Luftning av membrantankarna gör att returslammet är syrerikt och rejektvattnet innehåller mycket ammonium.Zonen fungerar som ett nitrifikationssteg då syret i returslammet kan oxidera ammoniumet från rejektvattnet. Dessutom kan zonen minska syrehalterna i returslammet för att undvika att det hamnar i pilotanläggningens fördenitrifikation. För att få bättre uppfattning om vad som sker i zonen och hur denna fungerar som ett nitrifikationssteg studerades nitrifikation, denitrifikation och syreförbrukningen i zonen. För att utvärdera RAS-DeOx-zonen belastades den med olika nivåer av ammonium från rejektvattnet vid olika hög luftning i membrantankarna. Detta utfördes både experimentellt direkt på pilotanläggningen och i en simuleringsstudie där processimuleringar genomfördes i en simuleringsmodell. I modellen utvärderades även två styrstrategier för zonen.Resultaten från studierna visade att både nitrifikation och denitrifikation förekom i zonen. Jämfört med simuleringsstudien varierade omfattningen av nitrifikation och denitrifikation mer i den experimentella studien. Båda studierna visade att det fanns risk att syre hamnande i pilotanläggningens fördenitrifikation. Styrstrategierna visade att det inte var fördelaktigt för pilotanläggningens resurseffektivitet att zonen luftades vid hög ammoniumbelastning från rejektvattnet. Det visade sig också att det var ingen större skillnad när det gällde pilotanläggningens prestation vid högt, lågt eller styrt returflöde för zonen. Däremot skiljde sig prestationen mer avseende luftning och koldosering.Utöver att det förekom nitrifikation och denitrifikation i zonen bedömdes den även fungera som ett nitrifikationssteg för ammoniumet i rejektvattnet. Dessutom minskade den syrehalterna i returslammet. Hur väl ammonium nitrifierades och syre förbrukades i zonen berodde på förhållandena i pilotanläggningen och förhållandet mellan mängden ammonium och syre i zonen. / At Hammarby Sjöstadsverk there is a pilot plant which is a smaller version of the future wastewater treatment plant at Henriksdal. Parts of the treatment process steps are membrane bioreactors. There is a zone in the pilot plant which is called RAS-DeOx to where the return activated sludge from the membrane tanks and the reject water from the sludge treatment are pumped. The return activated sludge contains oxygen since the membranetanks are aerated and the reject water has high contents of ammonium.The zone works as a nitrification step for the ammonium in the reject water, and also reduces the oxygen levels in the return sludge to avoid oxygen in the pilot plant's pre-denitrification step. To aquire a better understanding of what occurs in the zone and how it functions as a nitrification step; nitrification, denitrification and oxygen consumption was studied in the zone. To evaluate the RAS-DeOx-zone it was loaded with different loads of ammonium from the reject water at different levels of aeration in the membrane tanks. This was evaluated both experimentally at the pilot and in a simulation model of the pilot. In the simulation model two control strategies for the zone were also evaluated.It was shown that both nitrification and denitrification occurred in the zone. Furthermore, both studies showed that there is a risk that oxygen occurs in pilot's pre-denitrification step if the ammonium load in zone was low. Then, all of oxygen in the zone was not consumed. As for the control strategies, it was shown that the benefits were low for the resource efficiency of the pilot when the zone was aerated during high loads of ammonium. The performance of the pilot was similiar for high, low and regulated return flows for the zone, but the aeration and carbon dosage in the pilot differed.Besides that both nitrification and denitrification occurred in the zone, it was also functioning as a nitrification step for the ammonium from the reject water. The oxygen from the return sludge was reduced as well. The extent of nitrification and consumption of oxygen in the zone depended on the circumstances in the pilot and the relationship between the amount of oxygen and ammonium.

As Kungsängens wastewater treatment plant is considering a move, it opens up a possibility to implement nitrogen recovery technologies that comply with current and future legislative requirements. Nitrogen recovery offers simultaneous treatment of wastewater and collection of concentrated ammonia products for fertiliser production. This can create a circular and sustainable solution by reduced energy consumption, greenhouse gas emissions and nitrogen pollution. Despite the large amount of research that has been performed on this topic, practical use at wastewater treatment facilities in Sweden are still scarce. The aim of the degree project was to identify nitrogen recovery technologies and investigate their potential impact at a new Kungsängens wastewater treatment plant. A literature review provided different nitrogen technologies and concept scoring was used to rank and score them. Gas permeable membrane and ammonia stripping ranked the highest and both have the potential to be implemented at Kungsängens current or possible new site. Simulations were used to identify the change in energy consumption and change in effluent water quality related to the implementation of a nitrogen recovery technology. Calculations were performed to reach thequantities of nitrogen that could be recovered, and it was found that the nitrogen recovery potential was 0,2343 ton/d using gas permeable membrane, and 0,2750 ton/d using ammonia stripping. By replacing artificial fertilisers with recovered nitrogen, 7,95 kWh/kg N could be saved using gas permeable membrane and 2,76 kWh/kg N could be saved using ammonia stripping. The degree project also provides insight into European and Swedish lawconformity and predictability. Finally, a discussion of environmental impacts, potential for nitrogen recovery, nitrogen policies, and energy savings was conducted. It was concluded that nitrogen recovery can create benefits due to avoided nitrous oxide emissions, avoided production of precipitation chemicals and decreased energy consumption for aeration. Compared to artificial fertiliser produced using the Haber-Bosch method, it was determined that a significant reduction of carbon dioxide emissions could be reached.