TREATMENT OF SEWAGE AIR : COMPARATIVE PERFORMANCE OF THE PACKED AND MIST SCRUBBER TECHNOLOGIES

Abstract

Laboratory test runs were carried out to compare the performance of the packed scrubber and the mist scrubber. Both the scrubbers were operated under different sodium hydroxide/sodium hypochlorite solution concentrations at different inlet gas concentrations of hydrogen sulphide (H2S), pHset values, or liquid flowrates. The packed scrubber can be operated to handle wide fluctuations in H2S concentration merely by adjusting the strength of the recirculating solution. Chemical consumption will vary according to system demands, and there is little penalty for recirculating excess chemicals. For the mist scrubber, which provides a longer contact time for mass transfer, the amount of the scrubbing solution needed is less, but the liquid concentration is higher and cannot be reused. The scrubbers' inherent differences in trait and technologies do not provide a good basis to compare the performance of the two scrubbers. However, there is a strong similarity in trend in terms of removal efficiency and chemical usage rate. Both scrubbers have good removal efficiency of up to 99 % for different H2S levels. If removal efficiency is targeted at more than 90 %, the amount of chemicals needed to remove 1 gram H2S increases quickly with increasing efficiency level, and will be many times more than the stoichiometric quantity. The chemical consumption rate of the mist scrubber will be many times more than that of the packed scrubber. Use of the two scrubbers to remove medium or high concentration H2S at wastewater facilities, e.g. at pumping stations or sewage treatment plants, is a viable technology.