The use of flyash in wastewater treatment and sludge conditioning.

Conventional waste treatment proc esses have little or no effect on many pollutants present in a given waste water. Secondary effluents often are found to contain residual organic ma terials which are resistant to complete breakdown by biological treatment processes. Some of the resistant (re fractory) materials commonly found in secondary effluents are ABS, tan nins, lignins, long-chain hydrocarbons, and long-chain fatty acids. In many instances before the water can be re used, these refractory materials must be reduced in concentration or com pletely removed. Moreover, their pres ence can interfere seriously with other stages of treatment either for the re moval of organic and inorganic sub stances or for disinfection. The de velopment of separation techniques which are suitable for reducing or re moving the refractory materials pres ent in secondary effluents at a reason able cost, therefore, becomes necessary. Many different methods have been evaluated for satisfactory removal of the refractory contaminants. They in clude chemical oxidation, ion flotation, foam fractionation, distillation, freez ing, adsorption, and ion exchange. At present, adsorption, which is highly ef fective, appears to be the most efficient and economical method.