Some Aspects of the Geochemistry of Liquid Waste Disposal

Abstract

Industrial waste liquids in volumes up to 29 million gallons are produced in the West Midlands. With the introduction of the Deposit of Poisonous Wastes Act and the pending Control of Pollution Act, information is necessary to allow planning of disposal of these wastes to conform with the law. The industrial waste liquids containing copper, nickel, zinc, cadmium, iron, lead and chromium are commonly deposited in a variety of sites. Three such facilities known as Walsall Wood Mine, Mitco and Betton Abbotts are present in the West Midlands. Each site represents a different geological environment, a disused coal mine in Middle Coal Measures, a disused brick pit in the Etruria Marl Series, and a clay lined glacial kettle hole respectively. Experiments were set up to determine whether the geological materials at the sites would react with wastes to remove the toxic materials. An attempt has been made to quantify the results, to determine the environmental pollution hazards produced by disposal at these sites. Solutions of the metals in acid were prepared and mixed with rocks from the sites, with montmorillonite, and with kaolinite. Samples of raw effluent were also used in a further set of experiments. The metal content of the liquids reacting with the rocks was determined prior to, and after reaction. The results show that reactions occur between the metal solutions, and the clay minerals to produce a decrease in the metal concentration of the solution. Similar results were obtained using raw effluent. Metals are adsorbed in varying quantities depending primarily on charge and on other secondary factors which are discussed. The quantity of metal adsorbed was found to depend on the clay mineral types eg montmorillonite adsorbs more metal than kaolinite. The pH of the medium is also a control in that adsorption for all metals increases by more than 50% between pH O and pH kh, From the resvits it is concluded that disposal to the ground under control of pH, and the type of material at particular sites, will not result in the production of environmental hazards arising from toxic metal contamination.