Seawater bittern for the treatment of alkalized industrial effluents

The efficacy of magnesium-enriched liquid bittern in the treatment of a variety of industrial wastewaters was investigated. Fresh samples of effluents collected from such industries as ceramic, pulp and cardboard, dairy products, marble tiles, tannery and ready-mix concrete were initially adjusted to pH levels of 11.4 +/- 0.1 by the addition of slaked lime. Serial dosages of liquid bittern were added, and the jar test technique was used to determine the impact of the process on a number of determinant parameters. The investigation also included bacterial population suppression, and carbonation involving the use of dry ice (CO2) to adjust the effluent pH in order to meet discharge standards. Thr liquid bittern, with a potential for mass production by solar evaporation of seawater in coastal areas, was found to be an effective and economic coagulant in the treatment of industrial wastewaters. Turbidity and total suspended solids removals have exceeded 95%, while the chemical oxygen demand removals ranged from 40 to 99%, depending on the type of industry. Besides its reduced bulk when compared to seawater as the Mg2+ sourer, liquid bittern has the added advantage of inducing the least increase in total dissolved solids in the treated effluent. A high degree of total and fecal coliform bacteria were removed from the supernatant liquid under the experimental conditions applied. Additions of (CO2) in amounts ranging from 3.8 to 36.6 ml/l depending on pH and alkalinity prior to carbonation of the effluent were needed to neutralize the alkalized industrial wastewaters. (C) 1999 Elsevier Science Ltd. All rights reserved.