Modelling the COD Reducing Treatment Processes at Sjölunda WWTP

University essay from Lunds universitet/Kemiteknik (CI)

Author: Tanya Klingstedt; [2015]

Keywords: Technology and Engineering;

Abstract: The main focus of this thesis was to evaluate the possibility of establishing a wastewater treatment model for the main COD removal parts in the water line of Sjölunda Wastewater Treatment Plant (WWTP) located in Malmö, in southern Sweden. The finalised model was used to simulate an increased load of on average 5,000 population equivalents (P.E.) per year due to population growth in Malmö. The aim was to investigate for how long the present configuration of Sjölunda WWTP can handle the increased load without deteriorating water quality or enlarging the plant. The third aim was to investigate a possible increase in biogas production due to the increased load. The construction, calibration and simulation of the wastewater treatment model were executed using the DHI software product WEST. The flow and concentration data used was provided by online measurements and lab analysis at Sjölunda WWTP. The four main sections modelled were the iron-based pre-precipitation with pre-settling, the primary clarifiers, the activated sludge lines and the secondary clarifiers. No parts of the waste sludge treatment processes were modelled, instead, the biogas production was analysed using simplified calculations. The calibrated result indicates that it is highly possible to create a wastewater treatment model for the main COD removal parts in the water line for Sjölunda WWTP. The calibrated result for the primary sludge and the waste sludge were difficult to evaluate due to both lack of data from Sjölunda WWTP and data of low quality. The greatest calibration complication was to keep high concentrations for total suspended solids (TSS) and phosphorus (PO3-4-P) in the activated sludge, extensive effort was therefore directed towards solving this complication. The calibrated results for the overflow from the primary clarifiers and the concentrations for total Kjeldahl nitrogen (TKN) and COD in the overflow from the secondary clarifiers were considered good calibration results. The results from the increased load simulations indicate that it is only possible to operate Sjölunda WWTP for an additional nine years without deteriorating effluent quality from the secondary clarifiers or enlarging the plant. The total yearly biogas production during year 0 (before the increased load started) was 800,000 Nm3. The total yearly production was on average increased by 47,000 Nm3 each year until the ninth simulation year where the total yearly production had reached a value of 1,220,000 Nm3. It was proposed for future work to continue the development of the wastewater treatment model of Sjölunda WWTP since it was proved to be possible to create a model. Especially well-conducted measuring campaigns were proposed to improve the model significantly and a biogas production study was proposed in order to improve and evaluate the calculations for the biogas production.

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