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    Comparative performance of RBC operated under pressure and open to the atmosphere at high loading conditions
    (MARY ANN LIEBERT INC, 2005) Berktay, A; Ellis, KV
    The aim of this research was to investigate the effects of pressure on aerobic biological wastewater treatment processes. For the purpose of the investigation two specially designed, identical, laboratory-scale rotating biological contactor (RBC) units were constructed. One of these was held in a steel pressure vessel while the other, as reference unit, was operated open to the atmosphere. The treatment capabilities of the pressurized unit, compared to those of the reference unit, were determined for a variety of organic loading rates at a 5-bar pressure. The unit under pressure was able to produce a much better effluent, in comparison with the reference unit when operating at higher loading conditions. The filtered BOD5 in the effluent from the unit under pressure was always less than 10 mgL(-1), whereas the sludge yield coefficient was as low as 0.21 kg dry solids/kg BOD5 removed, even with the unit loaded even at an organic loading rate of 27.0 g BOD5/m(2) (.) day. However, the development of the nitrification decreased sharply as the organic loading increased. The indication is that the unit under pressure is able to operate over a wide range of loading with a small variation in the effluent quality. The principal benefits of increasing pressure were recorded to be significantly improved nitrification and a decrease in the sludge yield coefficient.
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    Comparison of the cost of the pressurized wastewater treatment process with other established treatment processes
    (PERGAMON-ELSEVIER SCIENCE LTD, 1997) Berktay, A; Ellis, KV
    A biological wastewater treatment unit under the influence of pressure was operated at pressures of up to 6 bar. It was demonstrated the capability of operating effectively with high carbonaceous oxidation and nitrification efficiencies at loadings of up to 13 g BOD m(-2) day. Another advantage of the pressurized treatment unit was observed to be its low sludge production. The cost of the pressurized treatment unit has, however, become an important factor for the applicability of the pressurized treatment unit. An investigation was carried out to determine the approximate cost of a proposed full-scale pressurized unit. The comparison between the pressurized unit and the established treatment processes were made for three populations of 500, 1000 and 3000 persons. The costs were then compared with those of various other conventional biological treatment processes capable of treating an equivalent wastewater load. The conventional processes selected for comparison were the activated sludge, biological filtration and conventional RBC. The sludge disposal cost for the pressurized unit was appreciably lower than that for the other processes. The results indicated that the cost of the pressurized unit (present value for a 20-yr period) and the costs of the activated sludge and conventional RBC processes were found to be similar for the smaller populations. However, a substantial saving could be obtained with the pressurized unit for the larger populations. In addition, there was an indication that the land requirement of the pressurized treatment unit decreased appreciably as the flow rate increased. (C) 1997 Elsevier Science Ltd.