On-site denitrification of nitrate-contaminated groundwater was conducted at 15 degrees C using a facultative psychrophilic denitrifier (strain 47) immobilized on macro-porous cellulose carriers and utilizing soluble starch as a non-toxic carbon source. A C/N ratio of 2.5 to 3.0 and a P/N ratio of 0.05 to 0.10 were found to allow complete denitrification of the groundwater used in this study. Under these conditions, the long-term performance of the system (4 months) was examined by decreasing the HRT (hydraulic retention time) from 4 h to 0.25 h. The process was stable and 95 to 100% of the influent nitrogen (NO3-N ranging from 13.0 to 16.5 mgl(-1) was removed until an HRT of 0.75 h was reached. The maximum NO3-N removal rate was 0.46 kg-Nm(-3)d(-1) at an HRT of 0.75 h. Nitrogen removal efficiency of 99.5% at an HRT of 1 h was obtained with a C/N ratio 2.58, corresponding to 4.3 g of soluble starch per 1 g of NO3-N.

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Nitrogen compounds in seawater are now contributing to serious water pollution problems. In this study, continuous removal of nitrogen in seawater using nitrifiers and denitrifiers immobilized in macro-porous cellulose carrier “AQUACEL” was examined. In nitrification, the nitrite oxidation step becomes the rate limiting step unless an influent inorganic carbon (g) / influent NH4-N (g) ratio (IC/NH4-N) of 7.23 is maintained. This is equivalent to an influent alkalinity (g) / influent NH4-N (g) ratio (ALK/NH4-N) of 8.25. Nitrite oxidizers were also sensitive to change in NH4-N loading. Unlike other biological removal systems used for seawater, trace element solution (containing Mo, Cu, Mn, Co, Fe, etc.) was added only at a high NH4-N loading rate of 0.65 kg-N/m3/carrier/d (at NH4-N concentration of 40 g/m3) and acclimatizing period was short, i.e., about a week. The maximum NH4-N loading rate obtained which removed 99 to 100% of the nitrogen compounds, was 1.30 kg-N/m3/carrier/d. For completion of denitrification, an influent phosphorus (g) per influent NO3-N(g) ratio (P/NO3-N) of 0.03 was required. Trace element solution (containing Fe, Mn, Mo, etc.) was doubled to 0.02% at NO3-N concentration of 560 g/m3. In addition, methanol concentration must be maintained at 30% more of the theoretical value of carbon concentration requirements. Copper enhanced nitrite reduction at an influent Cu(g) per influent NO3-N(g) ratio (Cu/NO3-N) of 0.002. The maximum allowable NO3-N loading rate necessary to remove about 99 to 100% of the nitrogen compounds was 20.79 kg-N/m3/carrier/d. This study reveakls that the AQUACEL system has high nitrifying and denitrifying capacities. The nitrogen loading capacity of denitrification is about ten times that of nitrification and is comparable to that of freshwater which also employed the AQUACEL system. In contrast, nitrogen loading capacity of nitrification is about six times less than that of freshwater, which indicates a higher sensitivity of nitrifiers to salinity. This indficates high sensitivity of the immobilized nitrifying bacteria to salinity. Morphological observations show that the ammonia oxidizers are a mixed culture ofNitrosomonas spp . and Nitrosovibrio spp., while the nitrite oxidizer is a Nitrobacter spp. The immobilized denitrifying bacteria showed similar morphological characteristics to the Hyphomicrobium spp.

Dehydrated and dried powdered sewage sludge (SW) was examined for use as an alternative to yeast extract (YE) to promote the degradation of lipid materials by a thermophilic oxic process (TOP). Its stimulatory effect on lipid degradation was found to be superior to that of YE. When 1.5 g of SW was added in combination with urea and 60 ml of a trace-element solution, the degradation efficiency was 82.9% for a 120-h treatment of 15 g of salad oil while that attained with YE was 68.3%. Although the degradation efficiency attained for animal fat, lard, was 77.8% which was lower than for vegetable oil, salad oil, it was still comparable to that obtained with YE, 76.9%. The applicability of SW to lipid degradation was confirmed in tests on three kinds of highly concentrated lipid wastes. With a nutrient supplement consisting of SW, a constant degradation efficiency of around 75% in 120-h treatment was attained for all lipid wastes despite their different features. The results of an elemental analysis suggested that the effectiveness of SW as a nutrient to stimulate thermophilic microbial activity in TOP was attributable to both a sufficient quantity and variety of amino acids and mineral components.

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The biodegradation of highly concentrated lipid wastes was conducted by a thermophilic oxic process (TOP). In order to improve the treatment efficiency of TOP, the stimulatory effect of nutrient supplementation was examined. A model nutrient supplement that satisfied the essential components necessary to promote degradation of lipid wastes was developed. The importance of balanced nutrient supplement consisting of organic and inorganic components was demonstrated. Regardless of the source of either vegetable oil or animal fat, the combination of 1.5 g of yeast extract, 1 g of urea and 60 ml of trace-element solution was effective to stimulate the degradation of 15 g of lipids by TOP. With this combination, degradation efficiencies of 68% and 77% in a 120-h treatment were attained for salad oil and lard, respectively. The conversion ratio of degraded lipid materials to CO2 was 0.91, confirming the advantage of TOP, i.e., very low excess sludge generation. The effectiveness of the model nutrient supplement for stimulating the degradation of lipid materials by TOP was also confirmed when tested on three kinds of actual highly concentrated lipid wastes. A constant degradation efficiency of around 60% in a 120-h treatment was attained for all lipid wastes although further improvement of degradation efficiency was possible by some nutrient addition into the model supplement combination. Based on the model nutrient supplement, the essential components for stimulating oil degradation by TOP and the possible alternative materials for the model nutrient supplement were discussed. The results demonstrated the possibility of employing TOP (stimulated by nutrient supplement) as a new biological treatment strategy for highly concentrated lipid wastes.