Anaerob psykrofil behandling av hushållsavloppsvatten i UASB
Utvärdering av kapaciteten hos en två-stegs UASB-reaktor för behandling av hushållsavloppsvatten
AnaerobicBlackwaterCODDomestic waste waterGranulesHammarby SjöstadPsycrophilicSedimentationSjöstadsverketUASB
Hammarby Sjöstad is a new district in southern Stockholm. A main objective with the Sjöstad project was to halve the environmental impact compared to other construction work. The environmental goals involve a halved water consumption rate, a local treatment of storm water and trials aiming to extract nutrients from the waste water. Sjöstadsverket is an experimental treatment plant used for testing new treatment processes for domestic waste water from Hammarby Sjöstad. The results are to be compared with the conventional process used at Henrikdals treatment plant today. Two aerobic and two anaerobic main treatment processes are to be tested before decision of full scale is taken in 2005.Anaerobic treatment without heating, as a way to reduce the content of organic material in the waste water, consumes less energy than conventional methods. Anaerobic reactors are usually operated at 37°C. It is possible to attain a high COD-reduction at lower temperatures, assumed a longer contact time between biomass and waste water. In an Upflow Anaerobic Sludge Blanket (UASB) - reactor the microorganisms form granules with excellent sedimentation properties. The granules are floating with the waste water flowing upwards through the reactor. This makes it possible to reduce the COD-content despite a short hydraulic retention time in the reactor.The two UASB-reactors examined in this thesis is a part of the pilot plant. The thesis shows how the startup of the reactors has functioned and evaluates the possibility to reduce the contence of different COD-fractions with this technique.The domestic waste water temperature has during the experiment period dropped from 23°C to 18°C. The total COD-content of the untreated waste water is 567 mg/l. Before the anaerobic step the water is pre-treated by adding of flocculation chemicals and sedimentation. The total amount of suspended material is reduced by 50 % in the pre-treatment and the load on the UASB-reactors is 100 mg/l. With a hydrologic retention time of 2,4 h the pre-treatment and the two-step anaerobic reactor has reduced 64 % of the total COD-content. Over the anaerobic treatment step the COD-reduction was 49 %. The reduction of dissolved COD (<0, 45 ?m) was 59 %. When operated in series the main part of the soluble CODreduction has taken place in the first reactor. After more than six months operation there is still a granulated sludge in the reactors and tests show a high metanogenic activity. Gas production from the reactors has been observed but not measured quantitatively.The results from this thesis show that anaerobic treatment with a UASB-process functions without heating for the household waste water from Hammarby Sjöstad. The anaerobic process should be combined with pre-treatment and supplementary treatment to reduce the remaining COD and the nitrogen and phosphorus content.