DIMETHYL-SULFOXIDE REDUCTION METHOD FOR T HE CHARACTERIZATION OF BIOMASS ACTIVITY IN SLUDGE OF AN AERATED LAGOON

The microbial biomass activity was studied in sludge from a wastewater lagoon (Hatzbachtal) which consisted of 4 aerated ponds and one polis hing pond. The lagoon was characterized by low BOD5 loading and high d ilution because of water from the surroundings. Sludge samples were ta ken from 4 sampling sites of each aerated pond and from one site of th e polishing pond. The biomass activity in the sludge samples was analy sed with the help of dimethyl sulfoxide reductase (DRA) and dehydrogen ase (DHA) activity. In addition, C-org-content was also determined. Th e effect of different reaction parameters on the DRA was studied in re lation to incubation period, temperature and atmosphere as well as slu dge weight and pH value. The results presented here show that a linear increase in the DRA occured for the sludge weight ranging from 0.1 to 0.5 g, incubation period from 0.5 to 11 h and incubation temperature from 20 to 50 degrees C. The pH spectrum from acidic to neutral did no t effect the DMS formation in sludge. Although the values for DRA were always higher in anaerobic incubation of sludge than in aerobic incub ation, the courses of the DRA in both conditions were parallel. Compar ing the biomass activity in sludge from different sampling sites of th e aerated ponds, the average C-org-content was found to be reflected b y the DRA, and DHA. Further, the variation in the DRA could represent also the influence of oxygen concentration. Therefore, a reduction in biomass activities indicated a decline in the availability of oxygen.