A method of treating solid waste in soil or solid disposed waste containing unacceptable levels of leachable metals, such as lead, cadmium, arsenic, zinc, copper and chromium, includes mixing the solid waste or soil in place with a phosphate source or a carbonate source or ferrous sulfate. After the solid waste and the additive are mixed, if needed an additional pH controlling agent is mixed into the soil or waste and additive. After the solid waste and additive and pH controlling agent are mixed under conditions which support reaction between the additive, pH controlling agent and metals, the metals will be converted to non-leachable forms which are relatively stable under normal environmental conditions. The treatment additives can be introduced and contacted with the soil or waste in any of the following techniques: spreading the additives on top of the soil or waste and mixing with a mechanical device, such as a rotary tiller, adding the treatment chemical through an infiltration gallery as a solution or slurry, injecting a soluble additive through injection nozzles or injection wells, and adding a treatment additive through a hollow-shaft auger and in-place mechanical mixing.

In situ method for decreasing heavy metal leaching from soil or waste

A method is shown for producing a lightweight aggregate by treating flyash and sewage sludge. The flyash and sewage sludge are mixed together and then agglomerated into pellets, with or without the use of a binder. The pellets may be coated and then are dried. The dried pellets are introduced into a rotary kiln in a direction that is co-current with the flow of fuel and air through the kiln. The pellets in the kiln will be indurated and will experience complete calcination as well as varying degrees of pyrolizing and sintering. The product of the kiln is a nodular material having a low density but with a hard and porous structure. The product of the kiln is feed to a cooler. The flyash sewage sludge mixture has a significant fuel value that is usable in the kiln. Furthermore, the fuel valve available in the kiln off-gases may be used for drying the materials.

Lightweight aggregate from flyash and sewage sludge

Class C fly ash may be activated with strong alkali to yield a novel, dense, quick-setting cement having unexpected properties. The setting time of the cement decreased as the pH of the activating solution increased. The microstructure and phase assemblage of the novel cement depended on the pH. Ettringite was absent beyond pH 14.30 (2.0N); a hexagonal plate-like crystalline form (stratlingite (gehlenite hydrate, C 2 ASH 8 ) and other compounds) became more abundant at higher pH. At higher pH the microstructure was characterized by high amounts of the plate-like crystalline phase and a dense matrix, due to higher reactivity of the glassy phase in fly ash. The novel cement will have uses in a number of areas, including fixation of hazardous wastes such as radioactive wastes, applications where rapid setting is desired, and formation of concrete in hot environments where ordinary Portland cements may tend to crack due to their heat of hydration.

Alkali activated class C fly ash cement

A process for forming an ash aggregate is provided. The process involves mixing a cellulose sludge material with an ash component. The ash component may comprise fly ash or sanitary waste ash in combination with fly ash. The sludge component preferably comprises paper mill sludge or pulp mill sludge. The hard lightweight aggregate may be utilized in a variety of manners, for example, to provide lightweight concrete and lightweight concrete mixes.

Process for forming aggregate; and product

A method of treating solid hazardous waste containing unacceptable levels of leachable metals such as lead and cadmium includes mixing the solid waste with lime and an agent selected from the group consisting of carbon dioxide and bicarbonate. After the solid waste and agent are mixed under conditions which support reaction between the agent and metals, the metals will be converted to nonleachable forms which are relatively stable under normal environmental conditions. If the solid waste material and agent are both dry when mixed, it may be beneficial to add water to facilitate the mixing of the solid waste and agent and the conversion of the metals into nonleachable forms.

M. Kenneth Chan

Papers

Process for using sludge from geothermal brine to make concrete and concrete composition