| Twelve lysimeters were constructed of 20 cm diameter PVC pipes filled with mixtures of incineration ash and compost. The lysimeters were vegetated and inoculated with the earthworm Eisenia foetida, and then irrigated with progressively increasing amounts of municipal waste activated sludge for six months. The purpose of the experiment was to evaluate the suitability of combining sludge irrigation, ash and compost utilization, and vermicomposting as a dedicated sludge treatment with leachate collecting systems. Primary emphasis was placed upon the concentrations, accumulations, and phytotoxic effects of heavy metal in the leachate, compost and the cover vegetation.;Eisenia foetida was able to prevent sludge surface crusting, maintain surface infiltration capacity, and eliminate malodors. The lysimeters reached a critical point at 12 cm/week application rate, as observed by decreased yield of tall fescue. Applied sludge was found capable of supporting the growth of new grasses but the growth of grass heights was inhibited. Iron was found not phytotoxic to the vegetation, but the uptake of magnesium, zinc, nickel and cadmium were limiting. Aluminum uptake by vegetation is expected to reach phytotoxic levels at high sludge irrigation rates. Nickel, chromium and iron in leachate were below the regulatory standards for discharge to surface and groundwater. Total coliform bacterial levels were dramatically reduced in the leachate. Coliform bacterial levels in vermicomposted sludge were still high and not significantly reduced through continued ingestion by E. foetida. |
