Leather/Skin/Hide Processing Industry - Environmental Clearance

I)Primary treatment is the first step of tannery effluent treatment and refers to the physicalchemicalseparation of the major pollutants from the raw wastewater, including suspendedsolids, sulphides and chrome removal, and the associated BOD and COD loadings. Primarytreatment usually evolves either settlement or floatation. Dissolved air floatation is nowadaysclassified as the best method to provide for most efficient primary treatment.W2O Environment, have implemented a new primary treatment plant at Articulos de Piel losFavoritos, CxA (Bermudez Tannery) which has been designed according to BAT (Bestavailable technology).3 The primary treatment comprises of effluent segregation andscreening, balancing, sulphide oxidation and dissolved air flotation (DAF).The dissolved air floatation system removes 70-80% of COD, discharging a clear andtransparent effluent containing less than 100 mg/l of suspended solids with an average CODof 1,004 mg/l. This new primary treatment plant, comprising of mixing + chemical treatment +floatation, shows a considerable improvement compared with the benchmark performance ofsimilar plants, according to the reference document of the IUE (International EnvironmentalCommission) and ‘Benchmarking: Part 4’,4 and can be considered to be one of the bestperforming primary tannery effluent treatment plants in the world.The tannery, based in the Dominican Republic, is producing leather from raw hides up tofinished leather for high quality markets. Articulos de Piel los Favoritos is now operating thismodern fully automated primary treatment plant, which conforms to European standards.ResultThe new primary effluent treatment plant at Articulos de Piel los Favoritos was started up inMarch 2008. The performance has been improved by testing various primary treatmentchemicals and selection of the most suitable polymer. In the following, the addition of theselected coagulants and polymers has been adjusted and a reduction of the overalltreatment chemicals has been achieved.The implementation of the new primary treatment has significantly improved the effluentquality and has also reduced the sludge disposal volumes and costs. The plant is fullyautomatic and requires minimum supervision.ConclusionsThe installation of a self-cleaning screen with a slot size of 1 mm has been shown toefficiently remove coarse solids and to protect pumps and Jetox Venturi used during thesubsequent treatment steps from wear and blockages.The sulphide oxidation using blower assisted Jetox Venturi aeration has been shown toefficiently remove sulphides with an average concentration of 0.19 ppm (data from2008/2009) achieved with the completion of the full 8-hour oxidation cycle.The Jetox Venturi aeration and mixing in the balancing tank has shown to completelyhomogenise the varying pH and to prevent solids settlement.