SUMMARYA total of 882 samples of settled sewage, sewage sludges and final effluents from eight sewage treatment plants were examined for the presence of salmonellas.Of these samples 68 % were positive, isolations being made most frequently from settled sewage (85 %), raw sludge (87 %) and anaerobically digested sludge (96 %).Fewer isolations were made from final effluent (24 %) and processed sludges (58 %). Samples usually contained less than 200 salmonellas/100 ml and arguments are presented that such concentrations should not lead to disease in animals if suitable grazing restrictions are followed.
The particular difficulties of sewage treatment in a Gulf State of the Middle East are highlighted. Ambient temperatures may at times exceed 50°C, and sand and dust can be a problem. A description is given of the sewerage and sewage‐treatment facilities at Al Ain in the United Arab Emirates, together with analytical data and flow records from commissioning until 1991. Attention is drawn to the problem of rapid anaerobic decomposition of sewage, consequent septicity, emission of foul odours, and hazardous hydrogen sulphide. There is a need for better control of this nuisance. Comment is made on high temperatures, and also on loss by latent heat of evaporation. The inability to reconcile sludge production with that indicated by empirical data, or predicted by sludge production formulae, is discussed.
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