Chemical Stabilization Processes Evaluated

The Central Contra Costa Sanitary District in Martinez (Calif.) examined chemical stabilization methods to control odours, improve dewaterability, increase the solids percentage and reduce pathogens in raw wastewater solids. This investigation was prompted by the need to find a suitable disposal site after the closure of the local landfill facility. Several chemical additions were examined including, potassium permanganate, ferric chloride, sodium hypochlorite, lime and other oxidants both in combination and separately. The best results were obtained from lime (at 0.2 kg per kg) for dewaterability with potassium permanganate (at 0.1 kg per kg) for odour control. A trailer-mounted pug mill mixer with a maximal throughput of 5400 wet kg per h was adopted for the pilot study, this being easy to operate although requiring much operator attention.