Water infrastructure on Aboriginal communities in Canada, and specifically Northern Manitoba is in sub-standard condition. A recent Government of Canada study indicated that an estimated $1.5 billion would need to be spent to improve this infrastructure. September 2003 through July 2004, an examination of the effectiveness of a membrane bioreactor (MBR) in a Northern Manitoban Aboriginal community took place. This study was intended to identify and test an appropriate and effective solution for the lack of adequate wastewater treatment in these communities. The MBR system, employing a Zenon ZW-10 ultrafiltration membrane, was designed and constructed at the University of Manitoba. It was installed and tested in two phases at the Opaskwayak Cree Nation Reserve in Northern Manitoba. Phase I was a direct comparison between the pilot-scale MBR and the community’s existing Sequencing Batch Reactor (SBR) with sand filter. This phase occurred from September 2003 until December 2003. The MBR, with an SRT of 20-days and an HRT of 10 hours, outperformed the SBR in every category despite 2 mechanical/electrical failures that resulted in the loss of biomass from the MBR. The SBR/Sand filter combination had BOD, TSS, and TKN concentrations of 30.3 mg/L, 27.5 mg/L, and 8.4 mg/L, respectively. By comparison, the BOD, TSS, and TKN concentrations in the MBR effluent were <6 mg/L, <5 mg/L, and 1.3 mg/L respectively. Phase II, from March 2004 through July 2004, tested the overall MBR efficacy and intended to assess a novel remote control and monitoring system. The MBR SRT was adjusted to 40-days and, as expected, the MBR MLVSS concentration increased to a relatively stable 5000 mg/L. The MBR continued to provide high quality effluent with some exceptions. Despite the 0.034 μm pore size, the total coliforms and TSS measured in the effluent were higher than in Phase I. This indicates a compromised membrane, faulty sampling procedures, or biological regrowth downstream of the membrane. This failure could point to the need for some form of tertiary disinfection. Also in Phase II, a remote control and monitoring program was implemented. The controlling PC was controlled via the internet using pcAnywhere software. The software allowed for real-time monitoring and complete control of the pilot system. In conclusion, the pilot-scale MBR yielded consistent, high quality wastewater effluent and this would benefit the pristine environments existing in Manitoba’s north. The potential hands-free operation could be utilized to provide support to communities lacking sufficient wastewater treatment know-how. / February 2006

The effectiveness of partial ozonation of return activated sludge for enhancing denitrification and waste sludge minimization were examined. A pair of nitrifying sequencing batch reactors was operated in either aerobic or alternating anoxic/aerobic conditions, with one control and one ozonated reactor in each set. The amount of solids decreased with the ozone dose. Biomass in the anoxic/aerobic reactor was easier to destroy than in the aerobic one, generating approximately twice as much soluble chemical oxygen demand (COD) by cell lysis. Increased COD favoured production of extracellular polymers in ozonated reactors, enhancing flocculation and improving settling. Floc stability was also strengthened in prolonged operation in alternating treatment, resulting in declined solids destruction. Dewaterability was better in alternating reactors than in aerobic ones indicating that incorporation of an anoxic zone for biological nutrient removal leads to improvement in sludge dewatering. The negative impact of ozonation on dewaterability was minimal in terms of the long-term operation. Ozone successively destroyed indicator estrogenic compounds, contributing to total estrogen removal from wastewater. Denitrification rate improved up to 60% due to additional carbon released by ozonation. Nitrification rates deteriorated much more in the aerobic than in the alternating reactor, possibly as a result of competition created by growth of heterotrophs receiving the additional COD. Overall, ozonation provided the expected benefits and had less negative impacts on processes in the alternating treatment, although after prolonged operation, benefits could become less significant. The alternating anoxic/aerobic reactor achieved twice the nitrification rates of its aerobic counterpart. Higher removal rates of estrogens were associated with higher nitrification rates, supporting the contention that the nitrifying biomass was responsible for their removal. The alternating treatment offered the better estrogen biodegradation. Microbial populations in both reactors were examined with fluorescent in situ hybridization. Dominance of rapid nitrifiers like Nitrosomonas and Nitrobacter (79.5%) in the alternating reactor, compared to a dominance of slower nitrifiers like Nitrosospira and Nitrospira (78.2%) in the aerobic reactor were found. The findings are important to design engineers, as reactors are typically designed based on nitrifiers’ growth rate determined in strictly aerobic conditions. / October 2008

Idag fokuserar företag mer och mer på att energieffektivisera sina verksamheter då det finns både ekonomiska och miljömässiga vinster i detta. För att minska energiförbrukningen i samhället är det bra att börja med dess infrastruktur. För att funktionen hos ett avloppsreningsverk ska vara god samtidigt som energikostnaderna hålls nere är bland annat valet av rätt pumpar och blåsmaskiner för den aktuella driftsituationen av största vikt. Att hitta balansen mellan funktion och energieffektivitet hos en kombination av maskiner är dock ett tidskrävande arbete. Genom två fallstudier och matematisk modellering var syftet med detta examensarbete att bestämma huruvida det är möjligt att grovt uppskatta livscykelkostnaden hos olika kombinationer av pumpar och blåsmaskiner i varierande driftsituationer. En sådan modell skulle hjälpa projektören att uteslutande undersöka de kombinationer av maskiner som är mest troliga att ha den lägsta livscykelkostnaden. Det har visats att det krävs en förmåga att mycket noggrant kunna förutsäga verkningsgraden hos de individuella maskinerna för att det ska vara möjligt att bestämma livscykelkostnaden så pass väl att resultatet är användbart. Sannolikt är det dock inte möjligt att finna en modell som är tillräckligt noggrann. Detta beror huvudsakligen på att mycket små förändringar av verkningsgraden ger en kraftig påverkan av livscykelkostnaden samt att verkningsgraden beror av många faktorer som är svåra att generalisera. Däribland att verkningsgraden inte förändras proportionellt till en varierande belastning på maskinen samtidigt som påverkan inte heller är densamma mellan olika maskinmodeller. Projektet har däremot mynnat ut i en ekvation för det flöde en blåsmaskin behöver generera i en given driftsituation samt ett beräkningsverktyg som underlättar undersökandet av de ingående parametrarnas inverkan på detta flödesbehov och därmed i förlängningen på livscykelkostnaden. Utöver detta slår rapporten fast att det i många fall är möjligt att sänka livscykelkostnaden med hjälp av icke frekvensstyrda maskiner. / Today companies tend to focus more and more on energy efficiency as there are both economical and environmental benefits to be gained. From a society’s point of view a good start to save energy is in its infrastructure. When designing wastewater treatment plants and their pumps and blowers choosing the right machines for the right operational circumstances is crucial to make it all work together and lower the energy cost at the same time. But to weigh the function against the energy efficiency of a combination of machines is a time consuming effort. Through two case studies and mathematical modeling this thesis project aimed to determine whether it is possible to roughly predetermine the life cycle cost of different combinations of pumps and blowers in variable operational circumstances. This would help the process engineers to focus their time and effort on the combinations of machines that are the most probable to have the lowest life cycle cost. The results show that the ability to accurately predetermine the efficiency of the individual machine is crucial to determine the life cycle cost to a usable degree. Unfortunately it doesn't seem feasible to find a model that will be accurate enough to be of practical use. This is due to the fact that slight changes to the efficiency cause great changes to the life cycle cost and that the efficiency depends on several factors that are hard to predict including the fact that it does not change proportionally to a variable load.

Microbial fuel cells were designed and operated using waste activated sludge as a substrate and as a source of microorganisms for the anodic chamber. Waste activated sludge provided a bacterial consortium predisposed to the solubilization of particulate matter and utilization of substrates commonly found in wastewater. Dissolved oxygen and ferricyanide were used as the electron acceptors in the catholytes. Microbial fuel cell comparisons were made while operating under identical conditions but using the two different electron acceptors. Comparisons were based on the electricity production observed during MFC operation, wastewater quality of the waste activated sludge anolytes and the community level physiological profiling of the microbial communities in the anolytes. Electrons liberated during substrate utilization in the anodic chamber traveled to the cathodic chamber where they reduced the electron acceptors. The anode and cathode chambers were connected by a Nafion ® proton exchange membrane to allow for cation migration. Various soluble carbon sources were dosed to the microbial fuel cells at measured intervals during operation via direct injection to the anolyte. During bovine serum albumin dosing, average power production levels reached 0.062 mW and 0.122 mW for the dissolved oxygen microbial fuel cell and the ferricyanide microbial fuel cell, respectively. These were 100% and 25% greater than the power production levels observed throughout the rest of the study. Increases in current production were observed following the dosing of sodium acetate, glucose and bovine serum albumin. No increase in current was observed following glycerol dosing. Sodium acetate dosing triggered an immediate response, while glucose and bovine serum albumin responded in approximately 2 minutes. A chemical oxygen demand mass balance was calculated for both microbial fuel cells. The lack of balance closure was attributed to unmeasured methane production. An accumulation of particulate waste activated sludge components was observed for both microbial fuel cells. The anolyte pH during operation was typically less than waste activated sludge pH, which was attributed to volatile fatty acid accumulation in the anolytes during fermentation processes. Community level physiological profiling was accomplished through the analysis of ecological data obtained with BIOLOG ® ECOplates. Samples were plated and analyzed under anaerobic conditions, mimicking the environment in the anode chamber of the MFCs. ECOplate data were transformed by a logarithmic function prior to principle component analysis. The community level physiological profiling indicated that shifts in the microbial community profile, as measured through the carbon source utilization patterns, occurred throughout acclimation and following the dosing of various carbon source substrates. Shifts due to glycerol dosing differed from shifts due to the dosing of sodium acetate, glucose and bovine serum albumin.

Aquatic eutrophication is a serious environmental problem that occurs all over the world. To protect surface waters (in particular the Baltic Sea), the regulatory pressure on onsite wastewater treatment (OWT) systems have increased in Sweden. Stringent requirements have led to uncertainties regarding the capability of conventional treatment techniques (soil treatment systems (STS)) to remove phosphorus (P), but they have also stimulated the development and introduction of enhanced P treatment techniques. In this thesis the accumulation and mobility of P as well as the chemical P removal mechanisms were studied in soils and reactive filter media. This knowledge was then used in environmental systems analysis. A model based on life cycle assessment (LCA) methodology was developed to evaluate the overall environmental performance of conventional and enhanced P treatment systems under various local conditions. The P accumulation in the studied STS varied (320-870 g m-3) and the accumulated P was rather mobile in some soils. Phosphorus compounds were identified in alkaline reactive filter media (calcium phosphates predominated) by means of X-ray Absorption Near Edge Structure (XANES). In sandy soils from STS aluminium was found to be a key element for P removal, as evidenced by a strong relationship between oxalate-extractable P and Al. The LCA studies indicated that enhanced P treatment systems may be beneficial from an eutrophication and P recycling perspective but causes increased impacts in terms of global warming and acidification. Despite the drawbacks, enhanced P treatment techniques should be considered suitable substitutes to surface water discharge STS under most conditions. This is because the latter systems have such a strong eutrophication impact. On the other hand, under appropriate conditions, STS with groundwater discharge may be advantageous. These systems generally caused low environmental impacts except for the dispersion of P resources. / <p>QC 20130419</p>

The presence of human pathogens in water indicates the sanitary risk associated with different types of water utilization. This study surveyed the sources of human pathogens in urban waters. In order to evaluate the microbiological water quality of urban water, the enumeration of various indicator bacteria (total coliform, fecal coliform, E.coli and enterococci) is usually used. The abundance of indicator bacteria in urban water indicates the level of fecal contamination and the presence of other human pathogens such as protozoan pathogens (Giardia lamblia & Cryptosporidium parvum). Fecal pollution of urban waters can be from human and animal origin. Point sources of fecal contamination in an urbanized area are the effluents of urban wastewater treatment plants. While non-point sources are usually originated from diffuse sources such as (runoff from roads, parking lots, pets, leaks, failing septic systems and illegal sewer connections to storm drains). urban stormwater is considered as a major carrier for delivering human pathogens from diffuse sources to receiving waters. Increases in urban stormwater volumes have resulted from increasing urbanization and growth of impervious surfaces. In order to reduce high amounts of human pathogens in urban waters, different methods are used nowadays to develop urban wastewater treatment plants technologies and urban stormwater management practices.

An analysis of a specific application of anaerobic wastewater treatment at a pulp and board mill, Stora Enso Skoghall, was carried out. A literature study was done and effluent wastewater from CTMP pulp production was analyzed. The analysis consisted of a broad constituent analysis and an anaerobic treatment trial. Results from these test where used to calculate the treatment effectiveness and resulting energy potential at the mill. The literature study and constituent analysis showed that toxicity of the water to be treated, due to wood extractives and sulphur content, was of concern. Detoxification chemicals targeting these constituents where used in the anaerobic treatment trial. The trial consisted of a two chamber upflow reactor and aerobic post treatment. The result of the trial is that the water of concern has about 50% anaerobically degradable content. A full scale implementation of anaerobic wastewater treatment would result in a methane production of 3,76 to 7,76 GWh/yr. An application of anaerobic wastewater treatment will also result in electricity savings, in aerated pond, and increase the capacity margin on current sludge handling techniques.

The most common way to treat wastewater in Sweden today is by a combination of an activated sludge process and a chemical treatment. These processes are not very energy efficient and may not be the most environmentally friendly. That is why it is interesting to evaluate new alternative methods to see if they can be less harmful to the environment and help to a lower resource consumption. New techniques are tested in a pilot installation at Hammarby Sjöstad, Sjöstadsverket. To be able to evaluate these techniques in a wide perspective system analyses are conducted where different impacts can be considered, advantages and disadvantages in the systems. Five system structures for water treatment have been constructed in Matlab/Simulink in this study. The URWARE (URbanWAter REsearch) model was used to conduct a system analysis, which made a comparison of the different systems possible. Four of the systems contained a new technique for water treatment, consisting of an anaerobic membrane bioreactor (MBR) combined with a VSEP (Vibratory Shear Enhanced Process) unit. This is one of the techniques that now are tested in Sjöstadsverket. The fifth system was a reference system designed as a conventional treatment plant. The wastewater treated in the different systems was in some cases mixed wastewater, in other source sorted, with or without food waste from kitchen waste disposers. Results from the system analysis shows that the MBR technique gives some advantages compared to the conventional water treatment. A large part of the nutrients in incoming materials are recycled. The highest recycling percent is reached when the MBR technique is combined with compost that handles the food waste. The total impact on the environment by greenhouse gases and eutrophic substances is lower in all the alternative systems compared to the reference system. The system with the source sorted urine has the most favourable exergy turnover. When reversed osmosis is used in the treatment a lot of energy is needed which leads to a poor exergy turnover and the conventional technique is more advantageous in these cases. All the alternative systems give a larger acidification which is a disadvantage with the MBR technique. / Vid behandling av avloppsvatten i Sverige används idag i de flesta fall en aktivslamprocess kompletterad med kemiskfällning. Denna process är inte så energieffektiv och kanske inte heller den mest optimala ur miljösynpunkt. Därför kan det vara intressant att utvärdera nya alternativa metoder för att se om dessa kan vara skonsammare mot miljön och bidra till en minskad resursförbrukning. I Sjöstadsverket, som är en försöksanläggning vid Hammarby Sjöstad, undersöks flera nya tekniker i mindre skala. För att kunna utvärdera dessa tekniker utifrån ett helhetsperspektiv görs systemanalyser, där för- och nackdelar och andra effekter kan vägas in. I föreliggande studie har fem systemstrukturer för vattenrening byggts upp i Matlab/Simulink. Substansflödesmodellen URWARE (URban WAter REsearch) användes för att utföra en systemanalys, som gjorde en jämförelse av de olika systemen möjlig. Fyra av systemen innehöll ny reningsteknik bestående av en anaerob membranbioreaktor (MBR) kopplad till en VSEP- enhet (Vibratory Shear Enhanced Process). Det är en teknik som nu testas i Sjöstadsverket. Det femte systemet var ett referenssystem utformat som ett konventionellt reningsverk. De vatten som behandlades i reningsverken var i vissa fall blandat avloppsvatten, i andra källsorterat, med och utan matavfall från köksavfallskvarnar. Utifrån systemanalysen kan det konstateras att MBR-tekniken ger en del fördelar gentemot den konventionella reningen. Bland annat eftersom en stor andel av näringsinnehållet i avloppsvattnet kan fångas upp och återföras till åkermark. Bäst kretsloppspotential fås när membranbioreaktorn kombineras med en kompost som tar hand om allt matavfall. Totalt sett bidrar också alla de nya reningssystemen till lägre växthusgasutsläpp och lägre utsläpp av eutrofierande ämnen än referenssystemet med konventionell rening. Ur exergisynpunkt är den nya tekniken bättre än den konventionella i det fall då urin källsorteras. I de fall då omvänd osmos används vid behandling är den konventionella processen mer fördelaktig. En nackdel med MBR-tekniken är att utsläpp av försurande ämnen är markant större än för den konventionella tekniken.

GE Healthcare operates in Uppsala (Sweden) and develops systems, equipments and medium to purify medical substances. Discussions with the local authority concerning planed far-reaching changes and upgrades of the biological process techniques for sewage management, aroused the question about revising the terms of permit for the activity. Therefore it seemed necessary to evaluate a newly installed biological process technique, which is the background of this thesis. The evaluated biological treatment process was built in 2003 and consists of a biological reactor filled with moving bed carriers with a high surface area for biological growth. At the time of the project the biological wastewater treatment plant consisted of a flow equalization facility and two following parallel biological processes; a biological reactor with moving bed carriers and a tower trickling filter. The aim of this thesis was to survey the function of the biological reactor with respect to the reduction of organic matter. Further to clarify which circumstances that have a negative effect on the organic reduction. During the three forthcoming years, an extensive reconstruction of the biological wastewater treatment facility will be accomplished. During the construction period the flow equalization will be very limited. Therefore an emission forecast with respect to organic matter was performed comprising the construction period during the years 2005, 2006 and 2007. This to estimate the safety margin to the emission standard during the construction period. Several parameters were surveyed during the project, water temperature, pH, plural nutrition elements, flow, oxygen concentration, suspended solids, organic load and microbial activity. At two occasions, the parameters were extensively studied during a 24-hour period respectively. Two capacity experiments were performed in order to evaluate the organic reduction at different organic loads. The obtained results together with an estimation regarding the organic load performed by AB Ångpanneföreningen were used for the emission forecast. The forecast considered two cases, operation with and without dosage of a flow with high organic content from the local solvent recycling facility (called T10-dosage). According to the forecast, the emission standard will be fulfilled during an average month regarding the organic load. This without T10-dosage and with an average reduction of 55 %. To fulfill the standard during a month with maximum organic load, a reduction of 65 and 75 % will be required in the cases without and with T10-dosage respectively. The organic reduction is negatively effected by lasting loads of 7 kg CODfilt/m3 or higher, or by a great increase of the load in a short period of time. Sporadic peaks regarding the organic load appeared to have temporary or no negative effects on the reduction. Flow variations during evenings, nights and weekends caused variations in the organic load with negative effect of the reduction rate. The oxygen concentration in the biological reactor has a conclusive significance of the reduction rate, a lower concentration than 2 mg/l affects the reduction rate in a negative way. The buffering capacity in the biofilm reactor showed to work excellently, the pH value varied between 6.8 and 8.9. There is an immediate risk of temperatures over 40oC during the construction period. This could have a negative influence of the organic reduction. Individual measured temperatures of 38oC did not have a negative effect on the reduction rate. The amount of suspended solids varied a lot in the outflow from the biological reactor and will continue to do so during the construction period. / GE Healthcare bedriver sin verksamhet i Uppsala vilken består av att utveckla system, utrustning och media för att rena läkemedelssubstanser. Vid diskussion med Uppsala kommuns VA- och avfallskontor väcktes frågan angående omprövning av tillståndet för verksamheten. Diskussionerna rörde planerade processförändringar och kompletteringar av bolagets biologiska processavloppsvattenrening. Av den anledningen ansågs det nödvändigt att utreda en för företaget ny processteknik för processavloppsvatten, vilket är bakgrunden till detta examensarbete. Den utvärderade processtekniken är en biofilmreaktor innehållande ett rörligt bärarmaterial med en stor skyddad yta för biologisk tillväxt. Biofilmreaktorn togs i drift under hösten år 2003 och därmed bestod det lokala reningsverket förenklat sett av en utjämningsanläggning följd av två parallella biosteg, ett biotorn med konventionell stationär biobädd över vilken processavloppsvatten spreds samt en biofilmreaktor med rörligt bärarmaterial. Syftet med examensarbetet var att kartlägga biofilmreaktorns funktion med avseende på reduktion av organiskt material. Vidare att klargöra vid vilka förhållanden reduktionsgraden har påverkats negativt. Under de tre kommande åren skall en stor om- och tillbyggnad av reningsverket genomföras. Förändringen kommer att medföra att utjämningsvolymen blir mycket begränsad under ombyggnadsperioden. Av den anledningen var ytterligare ett syfte med examensarbetet att utföra en utsläppsprognos med avseende på organiskt material för åren 2005 till och med 2007. Detta för att bedöma säkerhetsmarginalen till utsläppsvillkoret under ombyggnadsperioden. Examensarbetet realiserades genom att kartlägga parametrarna organisk belastning, organisk reduktion, vattentemperatur, pH, närsalter, flöde, koncentration löst syre, suspenderad substans samt mikrobiell aktivitet. Därutöver utfördes två kapacitetsförsök för att kartlägga den organiska belastningens inverkan på reduktionen. Vid det ena försöket skapades en högre organisk belastning genom att successivt öka flödesbelastningen över biofilmreaktorn. Vid det andra försöket doserades en delström (kallad T10-dosering) innehållande rester från den lokala lösningsmedelsåtervinningen med stort organiskt innehåll. Därtill utfördes två dygnsprovtagningar för att kartlägga ett flertal parametrars dygnsvariationer. Den framtagna utsläppsprognosen baserades på en belastningsprognos utförd av AB Ångpanneföreningen samt den i arbetet kartlagda reduktionen av organiskt material vid olika belastningar. Prognosen omfattar två fall, med eller utan T10-dosering. Enligt utsläppsprognosen kommer utsläppsvillkoret inte att överskridas under åren 2005 till och med 2007. Detta gäller vid en för året genomsnittlig månad avseende belastning utan T10-dosering och med en genomsnittlig organisk reduktionsgrad på 55 %. Under en månad med maximal belastning krävs 65 % reduktion och 75 % med T10-dosering. Kapacitetsförsöken visade att reduktionsgraden påverkades negativt vid en varaktig belastning överstigande 7 kg CODlöst/m3 samt vid kraftiga belastningsökningar. Tillfälliga belastningstoppar hade endast kortvarig eller ingen negativ inverkan på reduktionen. Höga flöden under dagtid och låga flöden under nätter och helger orsakade variationer i den organiska belastningen, vilket hade en negativ inverkan på reduktionen. När koncentrationen löst syre i biofilmreaktorn understeg 2 mg/l påverkades mikroorganismerna negativt och därmed även reduktionen. Buffertkapaciteten i biofilmreaktorn var god under den studerade tidsperioden och pH-värdet varierade mellan 6,5 och 8,8. Under ombyggnadsperioden föreligger en stor risk för att vattentemperaturen kan bli för hög i biofilmreaktorn vid ett flertal tillfällen. Enstaka uppmätta temperaturtoppar på 38°C påverkade dock inte reduktionen negativt. I biofilmreaktorns utgående vatten varierade mängden suspenderad substans kraftigt, vilket även kommer att gälla under ombyggnadsperioden.

Hallsta paper mill uses large amounts of water during the pulp and paper making processes. The wastewater is treated in two separate activated sludge processes referred to as BIO 1 and BIO 2. The main aim is to reduce the organic substance content, measured as COD (Chemical Oxygen Demand) before the wastewater is released into the environment. Since the effluent produced is very rich in organic substances, the addition of nitrogen (N) and phosphorus (P) are necessary to give satisfactory treatment results. Problems with sludge bulking sometimes occur which lead to increased levels of suspended matter and nutrients in the effluent. Periods of high concentration of phosphorus is also of great concern. The aim of this study is to investigate the causality behind the sludge bulking, with the help of scientific literature and analysis of previously compiled data using multivariate data analysis. COD and nutrients present in the influent will also be surveyed to identify variations in concentration caused by the paper making process. The scientific literature points toward low nitrogen and phosphorus levels as the major causes of the bulking sludge, as this leads to increased growth of filamentous bacteria to the detriment of the preferred flocculating species. A full scale experiment was conducted in an attempt to evaluate sufficient dosage levels of N and P to reduce this problem. The experiment has produced stabile results with low percentages of suspended organic matter and nutrients. Evaluation of the previously collected data using Multivariate Data Analysis did not lead to any correlation between variables being found, other than the impact of sludge concentration on COD-reduction. No relevant explanation to periods of high phosphorus levels could be found neither in the scientific literature nor in the multivariate data analysis. Bleaching of the paper pulp, with hydrogen peroxide and lye, results in a subsequent increase in COD concentration in the wastewater. The study shows an increased COD in the water approximately 12 hours after the increased dosing of these bleaching agents. Also the amounts of easily degradable COD increases following increased dosage of hydrogen peroxide and lye. The content of easily accessible phosphorus in the influent represents a minimum of 25 % and 20 % of the amount theoretically required for BIO1 and BIO2 respectively. The influent levels of nitrogen represents 33 % and 100 % for BIO1 and BIO2 respectively. From this study it has been possible to deduce that a controlled dosage of nutrients in relation to the incoming level of COD, is of great importance to the efficient treatment of COD rich effluent in the systems under investigation at Hallsta Papermill. / Vid Hallsta Pappersbruk används stora mängder vatten vid tillverkningen av massa och papper. Det förorenade processvattnet renas i två separata anläggningar, BIO1 och BIO2, båda med biologisk rening av typen aktivt slam. Avloppsvattnets höga halter av kolföreningar, vilka analyseras som COD (Chemical Oxygen Demand), kräver extra tillsats av kväve och fosfor för att erhålla tillfredsställande reningsresultat. I den biologiska reningen uppstår periodvis problem med slamsvällning, något som resulterar i höga utsläpp av suspenderat material och organiskt bundna näringsämnen. Även perioder med höga fosforutsläpp förekommer. Syftet med examensarbetet är att genom litteraturstudier och analys av historiska data, med hjälp av multivariat dataanalys, utreda orsakerna till problemen. Även en kartläggning av variationerna i inkommande avloppsvatten med avseende på COD och lättillgängliga näringsämnen genomförs. Utifrån information från litteraturen tyder problemen med slamsvällning ofta på bristande tillgång på kväve och fosfor vilket bland annat kan resultera i kraftig tillväxt av filamentösa bakterier. För att komma till rätta med problemen startades ett styrt försök med beräknade optimala doseringskvoter. Försöket resulterade i stabil drift för båda anläggningarna med låga utsläppsnivåer av både suspenderat material och näringsämnen. Resultatet från utvärderingen av driftsdata med multivariat analys visar att slamhalten har betydelse för COD-reduktionen i BIO1. Någon förklaring till problemen med höga fosforutsläpp har inte framkommit vare sig ur litteraturstudie eller multivariat dataanalys. Vid alkalisk oxiderande blekning av termomekanisk pappersmassa ökar den totala COD-koncentrationen i avloppsvattnet i samband med höjd dosering av blekkemikalier. Studien visar att en ökad COD-koncentration kan observeras i vattnet in till BIO1 ca 12 timmar efter förhöjd dosering av blekkemikalier. Samtidigt ökar andelen lättnedbrytbart COD till följd av ökad blekningsgrad. Kartläggningen av inkommande vatten visar att mängden lättillgängligt kväve i avloppsvattnet in till biologierna motsvarar ca 33 % och 100 % av det teoretiskt beräknade behovet för BIO1 respektive BIO2. För fosfor uppgår motsvarande till minst 25 % respektive 20 % för BIO1 och BIO2. Under examensarbetets gång har det kunnat konstateras att dosering av närsalter i förhållande till inkommande mängd COD är av stor vikt för en väl fungerande rening av det COD-rika avloppsvattnet vid Hallsta Pappersbruk.