Development of quantitative methods for the detection of enteroviruses in sewage sludges during activation and following land disposal

The development and evaluation of methods for the quantitative recovery of enteroviruses from sewage sludge are reported. Activated sewage sludge solids were collected by centrifugation, and elution of the solid-associated virus was accomplished by mechanical agitation in glycine buffer at pH 11.0. Eluted viruses were concentrated either onto an aluminum hydroxide floc or by association with a floc which formed de novo upon adjustment of the glycine eluate to pH 3.5. Viruses which remained in the liquid phase after lowering the pH of the glycine eluate were concentrated by adsorption to and elution from membrane filters. The method of choice included high pH glycine elution and subsequent low pH concentration; it yielded an efficiency of recovery from activated sludge of 80% for poliovirus type 1, 68% for echovirus type 7, and 75% for Coxsackie virus B3. This method was used to study the survival of naturally occurring virus in sludge at a sewage treatment plant and after subsequent land disposal of the solids after aerobic digestion. Reductions of enterovirus titers per gram (dry weight) of solids were modest during sludge activation but increased to a rate of 2 log₁₀/wk after land disposal.