Environmental Concerns of the Tanning Industry

Abstract

Tanning industry wastes pose a serious environmental impact on water (with its high oxygen demand, discolouration and toxic chemical constituents), terrestrial and atmospheric systems. Tannery waste characteristically contains a complex mixture of both organic and inorganic pollutants. The major public concern over tanneries has traditionally been about odours and water pollution from untreated discharges. Important pollutants associated with the tanning industry include chlorides, tannins, chromium, sulphate and sulphides, organic chemicals pesticides, dyes and finishing agents. These substances are frequently toxic and persistent, and affect both human health and the environment. High pollutant loads, involving chromium, can interfere with key biological processes used in sewage treatment plants. These pollutants may also damage the ecology of the receiving waters in the vicinity of the discharge points. Direct contact with some industrial chemicals can cause disability, illness (toxigenic/carcinogenic) and death in humans. Chlorophenols are the most predominant phenolic compounds in the tanning industry and are well known for their biocidal activities and have been found to be toxic, possibly mutagenic to terrestrial biota. Chromium appears to be the most damaging of these wastes, and in its hexavalent form it has a high level of toxicity, with chronic effects associated with cancer. The main contaminants and pollutants related to the leather sector are discussed in this chapter.