PREPARATION OF MARINE NITRIFYING SLUDGE

Activated sludge taken from night soil treatment plants which employ a sea-water dilution system to decrease the temperature elevation cause d by fermentative heat during operation was proved to be a good seed s ource for the preparation of acclimated marine nitrifying sludge (AMNS ). The preparation of AMNS with high nitrifying activity was successfu l from seed activated sludge obtained from a night soil treatment plan t which uses a sea-water dilution system throughout the year, within o nly a two-month acclimatizing period, by applying the fill and draw cu ltivation method. The nitrifying activity of our newly prepared AMNS w as 13.1 mg-NH4-N/g-MLSS/h, which is comparable to that of fresh water nitrifying sludge. The AMNS was composed of 50 to 100 mum bacterial fl ocs and showed an excellent settling property. The AMNS exhibited high nitrifying activity, even at a low sodium concentration, but its acti vity decreased at sodium concentrations above 10 g/l. The optimum pH f or nitrification by the AMNS was 8.5 and its nitrifying activity did n ot greatly change within the pH range of 7.0 to 9.0. The optimum tempe rature for nitrification by the AMNS was 35-degrees-C. The nitrifying reaction of the AMNS was proved to be less sensitive to temperature ch ange.