At Kungsberget ski-resort in Gävleborg county all wastewater produced at the facility is treated on-site. The treatment takes place at their own wastewater treatment plant in a so-called Sequence Batch Reactor (SBR), which has been in operation for about a year before this study. Kungsberget AB is currently in charge of the facility but their goal is to hand responsibility over to Sandviken Energy AB. In order for this handover to occur Kungsberget has to produce three approved treatment results. This means that the concentrations of BOD7 needs to lie under 0.3 mg/l and total phosphorous under 10 mg/l in the effluent water for three consecutive samples. The results show momentaneous values. These limits are stated in the permit Kungsberget received from the Environmental Protection Division. Kungsberget has had problems with high and fluctuating phosphorous concentrations and therefore the transfer has not yet taken place. In this project several parameters have been analysed in order to obtain an overview of prevailing influent and effluent concentrations. Some of the parameters that have been analysed are; phosphorous, nitrogen, BOD7, suspended solids and pH. A lot of time and effort has been put into elucidating operational routines at the wastewater treatment plant (WWTP) and gaining knowledge from available literature regarding different parameters’ effect on treatment results.   Kungsberget has had problems adapting operating routines and reaching stable treatment results as the load is highly effected of seasonal fluctuation. This has not been taken into account earlier and the WWTP has been operated in the same manner all year around. Suggestions to how operating routines can be modified in to better meeting the needs have been produced and alternative treatment methods have been presented in the report. Two of the suggestions include biological phosphorous removal and adding carrier media to increase bacteria growth. An aerobic solids retention time has been calculated in order to evaluate whether nitrifying bacteria have enough time for grow and maintain a stable population. The calculation was carried out by measuring suspended solids and aeration time and the result was a solids retention time of approximately 6 days.

The Cannibal system, comprised of an activated sludge process integrated with a side stream anaerobic bioreactor, is capable of reducing excess sludge up to 60% compared to the conventional activated sludge process. The hydraulic retention time (HRT) in the Cannibal bioreactor and the interchange rate (the percent of sludge by mass interchanged between the activated sludge system and the bioreactor on daily basis) are the two important operational parameters in the optimization of the Cannibal process. This research was designed to investigate the effect of the Cannibal bioreactor hydraulic retention time and the interchange rate on the solids destruction in the system. The first phase of this study has looked at the effect of three different HRTs, 5 day, 7 day and 10 day. The interchange rate during phase I was 10%. The results showed that the 7 day HRT can be recommended as the minimum retention period for the Cannibal process. The 5 day HRT Cannibal system had some settling problems and high volatile fatty acid content compared to the 7 day HRT Cannibal system. The protein and polysaccharide tests showed that the Cannibal bioreactor is primarily involved in the release of biopolymers which are degraded in the aerobic environment. The second part of this study focused on the effect of the interchange rate (IR) on the solids destruction in the system. The interchange rates that were applied in the system were 15%, 10%, 7%, 5% and 4%.The HRT in the Cannibal bioreactor was 7 day. The results showed that the 10% interchange rate gave maximum solids destruction than the other interchange rates. This implies that 10% is an optimum IR for the Cannibal system. Apart from higher solids wastage, the 4% and 5% IR Cannibal systems had higher volatile fatty acid production. / Master of Science