Drying Of Digested Biosolids For Weight Reduction Prior To Disposal

Disposal of belt filter pressed digested sludge (known as biosolids) to landfills cost El Paso Water about $1.1 million in the past year. With an increasing population, the amount of influent wastewater to El Paso treatment plants will also increase, resulting in increased biosolids generation and biosolids disposal costs. A method for reducing biosolids transportation cost is biosolids drying.The cost that El Paso Water pays for transporting biosolids to a dedicated landfill facility is based on the weight of the biosolids that are carried. Biosolids collected from the belt filter presses is about fifteen percent solids by weight, with water accounting for the rest of the weight. Essentially, El Paso Water is paying to transport water out of its wastewater treatment plants. Arid climates have great potential for biosolids drying because of the high temperatures and low humidity throughout the year, especially during summer months. Drying tests conducted in this investigation incorporated different mechanisms for breaking biosolids into smaller particles, including the use of a shredder, a greenhouse and fans for drying the biosolids particles. The drying tests showed that small biosolids particles exposed to warm air inside a greenhouse lose about 50-60% of the original weight. This weight reduction can lead to proportionate transportation cost reductions