Nitrogen removal in baffled waste stabilization ponds

This study evaluated nitrogen removal in Baffled Waste Stabilization Ponds (BWSPs) comprising laboratory and pilot-scale ponds with different number of baffles. The aim was to promote the waste stabilization pond practice for wastewater treatment in tropical countries by increasing nitrogen and organic carbon removal efficiency or reducing the land area requirement through the use of baffles which increased the biofilm biomass concentrations. The experiments started with a tracer study to find out the hydraulic characteristics of each pond. It was shown that the dispersion number decreased with increasing flow length and number of baffles which indicated more plug flow conditions. The deviation of actual HRT from theoretical HRT was computed and the flow pattern suggested the existence of an optimum spacing of baffles in BWSP units. The investigations further revealed that more than 65% TN and 90% NH3-N removal efficiencies were achieved at HRT of 5 days in a 6 baffled pond, which corresponds to the specific area of 34.88 m2m3. TN and NH3-N removal increased with increasing number of baffles in the BWSP units. Combined algal/bacterial biofilm grown on the baffles immersed in the ponds showed potential for increasing the extent of nitrification. COD removal increased with higher number of baffles with its maximum removal efficiency at 6 baffles. Compared with normal WSP, BWSP gave higher TN, NH3-N, COD and BOD5 removal efficiency. The effluent SS concentrations from the laboratory-scale 6 baffled pond were less than 20 mg/L at HRT of 3 days or more.</jats:p

Roles of baffles in waste stabilization ponds

Performance of baffles in waste stabilization ponds (WSP) comprising laboratory-scale ponds with different number of baffles was evaluated. This study was aimed at promoting waste stabilization ponds practice for wastewater treatment in tropical countries by reducing the land area requirement through the use of baffles which increased the biofilm and biomass concentrations. The experiments started with the tracer study to find out the hydraulic characteristics of each pond. It was shown that the dispersion number decreased with increasing flow length and number of baffles, which indicates more plug flow conditions. The deviation of actual HRT from theoretical HRT was computed and the flow pattern suggested the existence of an optimum spacing of baffles in baffled waste stabilization pond (BWSP) units. The investigations by feeding with synthetic wastewater further revealed that more than 65% TN and 90% NH3-N removal were achieved at HRT of 5 days in 6-baffled pond which corresponds to the specific area of 35.20 m2/m3. TN and NH3-N removal was increasing with number of baffles in the BWSP units. COD removal increased with higher number of baffles with its maximum removal efficiency at 6 baffles. The computed COD removal encompassed first-order reactions of both suspended and biofilm biomass was higher than that without the biofilm biomass activity and agreed well with the observed data. Compared with normal WSP, BWSP gave higher TN, NH3-N and COD removal. The effluent SS concentrations from 6 baffled-pond were less than 20 mg/l at HRT of 3 days.</jats:p

Sanitation Program Development for Rural Thailand in Relation to the International Drinking Water Supply and Sanitation Decade

The sanitation level in the villages of Thailand is still generally low despite the past efforts of the Sanitation Division of the Department of Health. Consequently, the Royal Thai Government (RTG) is embarking on a national sanitation program with a view to minimizing the occurrence of excreta-related diseases in the rural communities, which will be implemented together with the rural water supply program, so as to produce the optimum effects on health. This dual program, otherwise known as the “Thailand Decade Plan,” will be initiated in 1985 and will continue until the end of 1991. The realization of this plan will serve as Thailand's commitment to the International Drinking Water Supply and Sanitation Decade (IDWSSD). With only 2.8 million pour-flush (PF) latrines installed up to the end of 1983, accounting for 44.3% of the total number of households, the plan calls for the provision of an additional 2.5 million PF latrines in order to achieve the target, which is to provide 75% of households with PF latrines by the end of 1991. Considering the attitudes and economic status of the Thai rural people, the proposed strategies for the implementation of the sanitation program will be the provision of material subsidies and/or “revolving funds,” with strong support from such activities as health education, especially for women and children, and the necessary training of personnel. Implementation of the plan will require an investment of approximately Baht 1,792.6 million (roughly U.S.$ 66.4 million).</jats:p

Separation of oil–water emulsion from car washes

The potentials of UF and NF membrane processes have been evaluated for separation of oil water emulsion generated from car washing operations. Using membranes, wastewater can be effectively recycled and fresh water usage could be reduced. The parameters studied were membrane type, emulsifier types, pressure and competing compounds. Both an-ionic and non-ionic emulsifiers were used for the experimental runs. The Ca2+ and Mg2+ were used as the main competitive ions. Results indicate that a polysulfone membrane caused more flux reduction than the cellulose acetate and thin film polyamide membranes. Higher concentrations of emulsifier presented negative flux decline in both UF and NF membranes. However, the presence of nonionic emulsifier in oil emulsion caused more significant flux reduction than an anionic emulsifier. The NF membrane produced higher TOC removal and less fouling than UF. The results indicate that increased competitive Ca2+ and Mg2+ ions resulted in significant positive NF flux and TOC removal.</jats:p

Application of air backflushing technique in membrane bioreactor

The optimum air backflushing and filtration cycle was investigated for a 0.1 μm hollow fiber membrane module immersed in an activated sludge aeration tank. It was found that 15 minutes filtration and 15 minutes air backflushing gave the best result both in terms of flux stability and net cumulative permeate volume. Although this cyclic operation could not completely remove the clogging, this process improved the flux by up to 371% compared to the continuous operation. During the long term runs, three different hydraulic retention times (HRT) of 12, 6 and 3 hours, corresponding to 0.16, 0.32 and 0.64 m3/m2.d of permeate flux respectively, were investigated. Stable operation was obtained at the HRT of 12 hours. Decrease in HRT led to rapid formation of a compact cake layer on the membrane surface thus increasing the transmembrane pressure. It was also noted that filtration pressure increases with increase in bioreactor MLSS concentration. With operation time, the MLVSS/MLSS value decreased without significant effect on the process performance, indicating that inorganic mass constantly accumulated in the bioreactor. All the experimental runs produced more than 90% removal of COD, and TKN. In terms of physical, chemical, biological and bacteriological parameters, the membrane bioreactor effluent was superior to the conventional activated sludge process.</jats:p

Final report on technological improvement of tapioca chips and pellets produced in Thailand

Report on the parameters affecting the drying and pelletizing of cassava chips in Thailand - discusses solar and artificial drying techniques, the chip pelleting process and testing of laboratory research results. Includes statistical data