Anaerobic water purification systems for textile and tanneries

Textile wastewater typically has high pH, high organic pollution, high salt concentration (in most cases sulphate), toxicity and colour. The composition of the wastewater varies per production process: desizing, scouring, dyeing and finishing produce completely different wastewater qualities.

The biggest problem is often colour and toxicity. Biological aerobic treatment alone does not suffice and the combination with chemical and physical treatment is very costly. Paques applies anaerobic and aerobic treatment where the concentration of COD is high enough and colour and toxicity need to be removed.

Research and experience have proven that only a combination of these technologies is really successful. COD removal in the anaerobic treatment is generally limited to 40-60%, the combination with aerobic removes 80-90%. With post-treatment technologies (TSS removal and adsorption/membrane techniques) Paques can design and build the best solution for treatment of textile wastewater, depending on the on the composition and types of dyes used.

Treatment of tannery wastewater produces high amounts of solid wastes, due to chemical precipitation and aerobic treatment. The resulting sludge has to be disposed of at high cost. Treated water also contains elevated levels of sulphate and chlorides. Many tanneries search for solutions to reduce the amount of solids produced in their wastewaters.

A combination of sludge digestion and anaerobic wastewater treatment not only reduces the amount of solid waste but also produces profitable biogas. The digestion stage can be extended to treat other tannery waste products such as fleshings and trimmings. Anaerobic treatment of high sulphate containing wastewaters is possible; after reducing sulphate to sulphide, the biological sulphide oxidation process efficiently removes the sulphide from either wastewater or gas by converting it into biosulphur.

The result is a sulphide-free effluent low in sulphate, without the need for sulphide precipitation using iron-based chemicals. Depending on final discharge limits, ANAMMOX® or aerobic post-treatment can be applied for nitrogen removal.