In order to size the anoxic reactors in nutrient (N and P) removal activated sludge plants, it is essential to know the denitrification kinetics that are operative in such systems. To date, denitrification kinetics have been accurately defined only for systems that remove N alone; little research has been performed on denitrification in N and P removal plants.

This master thesis gives an account for various aeration schemes that are utilized in conventional activated sludge treatment process in a wastewater treatment plant. By altering between different aeration schemes, the project aimed at reducing energy consumption along with maintaining the treatment performance at the plant. A series of experiments on the treatment performance over several different aeration schemes thus has been conducted on site at Solviken in Mora, Sweden. The project is basically a case study where no parameters were manually controlled except for the aeration schemes at the plant. Energy consumption reduction is logically relative to the ratio between aeration and non-aeration intervals. Several criteria were tested in regards to the treatment performance, including pH value, organic matters, phosphorus substances and microorganisms. The study has come up with a superior aeration scheme for the plant, as well as indicated processes that can be improved at the plant.

This paper is about improving the efficiency of nitrogen and other organic nutrient removal from activated sewage treatment by adopting an innovative technology. The work is to study the changes in nitrogen removal in pilot-scale experiments with the ITEST unit. The report also describes the various sources contributing to the eutrophication of the sea and water, caused by an increase in nutrient levels in different water bodies. Ineffective treatment of sewage contributes to the eutrophication. In the Baltic regions the temperature will be zero (0) or less than zero degree-centigrade during winter season. It results in decreased or fall in temperatures of incoming water to wastewater treatment plants. The temperature is an important parameter for sewage/wastewater treatment processes. Bacteriological nitrification and denitrification is an effective process for removing nitrogen from wastewater. From various research works and articles, it can be found that 23 + / - 2 °C, is the optimum temperature for nitrification and denitrification processes. So, the main aim is to study the effect of maintaining the incoming wastewater temperature by use of heat exchangers on incoming water to an activated sludge process line in pilot plant scale. In the pilot plant there were two testing lines; one line with heating system and the second line without heating system. A temperature of 19 to 20 °C was maintained in the influent to testing line. The nitrogen removal rates were compared between the two lines during the test period of approximately more than 8 months. Other biological activities in the treatment process were also compared between the two lines.

A big challenge within pulp and paper mills is the large quantities of waste activated sludge (WAS) that is produced during the wastewater treatment. The WAS is made up of biological cells and extra polymeric substances (EPS) and can bind a large amount of water causing difficulties to dewater the WAS. This study aimed to determine how to improve the dewatering properties of the WAS by using hydrolysis. Hydrolysis will cause the cells to disrupt and the bound water in the cells and the water trapped by the EPS can be released. Specifically, this study investigated what impact hydrolysis with heat, alkalis, and acids had on the WAS dewatering properties. In addition to the impact on the dewatering properties, the release of organic material and nutrients from the cells has also been important for biomethane production. In this study, it was specifically NH4-N, PO43- and COD that have been studied. WAS from paper mills have in general poor methane potential so it was of interest to see how the WAS was affected by hydrolysis and how hydrolysis could improve the methane production. To test the hypothesis of whether hydrolysis could affect the WAS and improve the dewatering properties, several experiments were performed. The experiments included thermal hydrolysis at temperatures of 70-90 °C, acidic hydrolysis with acids such as spent acid and acid water, and alkalis such as green liquor sludge and EOP. All acids and alkalis used in the study were chemicals that exist at the paper mills included in this study. To test the dewatering properties, methods such as TS analysis on the accept, CST-analysis, and a belt press were used. Analyses were also performed on the reject to measure the suspended solids and the nutrients NH4 – N, PO43– and COD in the WAS. This study did also determine what effect hydrolysed WAS had on the biomethane potential. In this study were the paper mills BillerudKorsnäs in Skärblacka and SCA in Östrand included. Hence was sludge from the two mills of interest to analyse. This study has shown better dewatering properties with an increase in the total solids (in the accept) after the thermal hydrolysis, the acidic hydrolysis with spent acid, and the alkali hydrolysis with green liquor sludge. Specifically did the acidic hydrolysis with spent acid improve the dewatering properties in terms of an increase in TS in %. The biggest increase in TS in % could be seen after using 10% spent acid ratio. The TS for the WAS from SCA Östrand increased in this experiment by 107 %. The thermal hydrolysis also showed promising results both in terms of dewatering properties and in the release of organic material. The biochemical methane potential test results showed a better and more rapid stabilized production of biomethane after hydrolysis of WAS compared to untreated WAS. The thermal hydrolysis both increased the rate of production and the total amount of methane produced. The thermally hydrolysed WAS from SCA Östrand improved the methane production from 77 Nml methane/g VS to 95 Nml methane/ g VS. The WAS from BillerudKorsnäs improved the methane production from 40 Nml methane/ g VS to 55 Nml methane/ g VS. These results, both from the methane potential tests and the results of the increased dewatering properties, show that the concept with hydrolysing should be evaluated further for improving the dewatering of the WAS.

This study describes the variation of an important greenhouse gas, nitrous oxide (N2O) at site-specific from the bio-lines unit at Wastewater Treatment Plant (WWTP) in Halmstad. The sampling campaign at the WWTP was carried out for three consecutive days during the weekdays in March 2021 with total of 144 samples were taken in GHG sample vials (exetainers) and analysed for N2O measurements using gas chromatography. Other nitrogen parameters data (NO2-N, NO3-N, and total nitrogen) were also collected. Using statistical analysis, comparisons were focused on a year period (March 2020 and 2021). This study found that N2O concentration generated in March 2021 was significantly lower than March 2020. Results also showed significant differences of N2O concentration between the three different zones (anaerobic, anoxic, and aerobic) among the bio-lines, where the highest N2O concentration was only found in aerobic zones. Correlation analysis showed only total nitrogen is negatively correlated with N2O-N in the aerobic zones. These findings will enable better understanding of processes along the bio-lines as a step for WWTP operators to improve N2O monitoring.

Analytical analyses conducted at the Himmerfjärden WWTP (285.000 PE connected) identified 70 pharmaceutical compounds belonging to different therapeutic classes. Such organic micropollutants at low detected concentration range of µg - ng l-1 did not affect the treatment processes at WWTP. Results from analytical studies indicated continuous discharge of organic micropollutants to the surface water with a calculated load amounting to 1.51 kg day-1. Metoprolol, carbamazepine and naproxen were chosen for testing different removal methods. Oxygen Uptake Rate (OUR) tests were conducted to assess the bacterial activity of an activated sludge taken from a full scale aeration plant with the presence of selected target compounds. A semi-technical scale membrane bioreactor ZeeWeed10™, treating final effluent from the Himmerfjärden WWTP (Sweden) was seeded with activated sludge from full scale biological stage. The membrane bioreactor (MBR) system placed after the final treatment appeared to be an insufficient technology for removal of residual amounts of organic micropollutants from WWTP effluents. Batch test studies with activated sludge taken from the membrane bioreactor and with application of granular activated carbon (GAC) filtration resulted in giving an overall assessment of removal efficiency. Metoprolol and carbamazepine tend to be resistant to the biodegradation process and in the dosed high concentration lead to bacterial cell decomposition in the activated sludge. Apparently, removal efficiency for naproxen exceeded the value of 46% with the spiked initial amount of 3.3 mg NAP g-1 MLSS. Application of the GAC filtration proved to be an efficient technique for removal of pharmaceutical compounds from treated wastewater. Application of the statistical programme Modde7 was a time saving tool in studies of fouling occurrence. The effect of fouling phenomenon, which is a highly limiting factor for MBR performance, was minimised by adjusting the operational parameters as predicted by the Modde7 programme. / QC 20101104

The recent technological advances in environmental monitoring coupled with the increasingly stringent effluent requirements being placed on waste treatment systems makes it vital to have a more complete understanding of how specific compounds in waste streams can impact wastewater treatment processes. Since activated sludge processes are recognized as one of the most often applied technologies in wastewater treatment, this study assesses the impacts of select toxic synthetic organic compounds (SOCs) on the activated sludge communities in two types of wastewater treatment reactors: a completely-mixed activated sludge reactor (CMAS) and a sequencing batch reactor (SBR). Commonly applied activated sludge monitoring parameters, such as solids analysis and substrate removal, are collected and correlated to the results of microscopic image analysis (IA) and direct gradient gel electrophoresis (DGGE) to monitor the response of the activated sludge communities to variations in operational conditions, including the incorporation of SOCs in the influent feed and varying the solids retention time. The results of this research indicate that the response of the activated community is highly dependent on the reactor configuration. The CMAS settling performance was more strongly correlated to the shape parameters, and the SBR settling performance was more strongly correlated to the size parameters, which is qualitatively supported by particle settling theory when considering that SBR flocs were found to be larger than the CMAS flocs. The SBR began to exhibit larger floc sizes and had a higher sludge volume index with the incorporation of SOCs, while the CMAS flocs became more spherical after SOCs were incorporated and exhibited more discrete settling. The molecular analysis results revealed that the community structure within the activated sludge system was transient in response to environmental variations. Banding patterns indicated that samples were more similar to other samples taken from the same reactor under the same operational conditions. Thus, as operational conditions were varied, sample banding patterns would also change, indicating transitions in the genetic composition, and ultimately the dominant species present, in response to environmental changes.

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