Koichi Fujie

Operational design and power economy of a rotating biological contactor

Abstract A method to estimate power economy, defined as the amount of BOD removed per unit power consumption of the rotating biological contactor (RBC) was developed. The characteristic value of the power economy as a function of operating conditions was evaluated and discussed. While the power economy of RBC under practical operating conditions is much higher than that of the activated sludge process, the BOD removal rate of RBC per unit floor area is rather small, only about one-third of the latter in its practical use. This renders the RBC not well suited for use in large scale wastewater treatment, but rather only for small scale treatment where the floor area of the RBC is not an important factor to reckon with in the plant. Since the influent fluctuation of wastewater reduces considerable power economy, in order to keep its high value the use of a flow balancing tank with the RBC unit is recommended.

Power economy characteristics of an activated sludge aeration tank

Abstract The air feed rate to meet a given oxygen uptake rate in the activated sludge aeration tank was expressed by using the concept of the air diffuser performance, previously proposed by the present authors. Using the relationship between the BOD removal and the oxygen uptake rate, a procedure to predict the power economy, which is defined as the amount of BOD removed per unit power consumption of the air feeding, and the effluent quality of the activated sludge process under various operating conditions was presented. The effect of operating parameters in the tank; the MLSS concentration; the hydraulic retention time and the BOD loading on the power economy and the effluent quality were extensively evaluated. The results calculated by the proposed procedure were compared with the statistic data of operating conditions in the municipal wastewater treatment plants in Japan. A method to improve the effluent quality while maintaining a high power economy was also discussed.

Method for monitoring the decomposition process in soil of organic wastewaters with high strength and low c/n ratio

Abstract Squeezed fluid of pig manure and bonito processing wastewater, and their effluents from methane fermentation were studied in pot experiments in a model case of land application of organic wastewaters with high strength and low C/N ratio. Kanagawa alluvial soil (upland soil) and Kagoshima volcanic ash soil (upland soil) were used. The stabilization period of these four wastewaters in Kanagawa soil determined by gel chromatography was 14 days for an effluent from methane fermentation of bonito processing wastewater (EMB), 21 days for an effluent from methane fermentation of squeezed fluid of pig manure (EMP) and bonito processing wastewater (BPW), and 28 days for squeezed fluid of pig manure (SPM). Stabilization of all wastewaters occurred 1 week later in the Kanagawa soil than in the Kagoshima soil. In spite of apparent stabiliza- tion, inhibition of the growth of a 72 h seedling of Komatsuna (Brassica campestris L. var. rapiferafroug) was observed in EMB due to the accumula- tion of N02-N especia...

EVALUATION OF POWER ECONOMY CHARACTERISTICS OF AEROBIC WASTEWATER TREATMENT PROCESSES

ABSTRACT The relationship between the power economy and the BOD removal rate per unit floor area or unit volume of the aerobic wastewater treatment processes, such as activated sludge, trickling filter, rotating biological contactor, fluidized bed, oxidation ditch, deep shaft aerator were investigated under their conventional operating conditions for the domestic wastewater treatment. It was clarified that the higher BOD removal rate per unit volume or unit floor area of the plants brings about the lower power economy. Appropriate selections of wastewater treatment processes and their operating conditions are significant to maintain the high quality effluent and the high power economy.