Abstract

Sanitary landfill leachates are treated usually by multistage systems using physical, chemical and biological processes. One of the most economic and efficient method is combined treatment of landfill leachates with municipal wastewater in a sequencing batch reactor (SBR. The main advantage of such co-treatment is that landfill leachates variability (in quality and quantity) do not influence the effectiveness of biological processes. The objective of this research was to study the possibilities of "young" landfill leachates treatment together with municipal wastewater in a laboratory scale sequencing batch reactor (SBR). The lab-scale SBR (V=5 dm3) was equipped with magnetic stirrer, an aquarium air diffuser, and on-line measurement of dissolved oxygen (DO) and pH. The raw mixtures of raw wastewater (RWW) with raw landfill leachates (RLL) were supplied and after treatment withdrew by peristaltic pump. The concentration of dissolved O2 in aerobic phase was set up 1.0-0.5 mg O2/dm3 while activated sludge concentration 3.5 g dry mass/ dm3. The total length of SBR cycle lasted 12 h, and was divided into: 60 min of filling, then two successive aerobic/anoxic periods (510 min) followed by the 30 min re-aeration step and 120 min of settling and withdrawal. Initially the SBR was inoculated with nitrifying activated sludge and during the start-up period (9 weeks) was fed only with the raw municipal wastewater (the activated sludge and raw municipal wastewater were both obtained from the Gdansk "Wschod'' WWTP). During the next 14 weeks, the system was fed with the mixture of raw municipal wastewater with increasing quantity of landfill leachates from 1 to 10% (vol.). The landfill leachates was originated from the Gdynia landfill ''Eko Dolina Lezyce". The obtained results indicate that landfill leachates addition from 1% to 10% (vol.) had negligible influence on the effluent quality (with the exception of total phosphorus (TP) and total nitrogen (TN)). Even thought the quantity of landfill leachates reached 10% (vol.), the effectiveness of chemical oxygen demand (COD), biological oxygen demand (BOD5) and total suspended solid (TSS) removal was at level over 90%. On the contrary, TP removal during the increased addition of leachates (vol.) was dropping from 72% to 35%. Despite the fact that the efficiency of TN removal achieved average value of 70%, and was increasing with time from 59% to 85%, average N-NO3 concentration in effluent was rather high 15mgN-NO3/dm3. Thus for optimalization of the denitrification process the external carbon source seems to be necessary. The extended removal of N-NO3 should also increase the biological phosphate removal.

Authors (7)