RESUMO
This study highlights the need for the development of simple, efficient, and cost-effective farm-scale applications to treat wastewater arising from vegetable-peeling operations. The aim was to evaluate two full-scale biological wastewater treatment systems, a sequencing batch reactor (SBR) and a biofilter, and a chemical wastewater treatment system on farms carrying out peeling of vegetables. The types, design criteria and parameters of the processes, as well as properties of the untreated and treated wastewaters were presented and evaluated. Seven-day biochemical oxygen demand (BOD7) entering the SBR was 3100 +/- 529 mg l(-1) (mean +/- standard deviation). The results showed that the SBR was very stable and effective in the treatment of carrot-processing wastewaters, the BOD7 for effluent being about 10 mg l(-1). The biofilter examined did not operate well because the pH too low: the reduction for BOD7 was 63% and, for COD, 58%. When wastewater from potato processing was treated with aluminium sulphate and conveyed to an artificial pond, removal of BOD7 was 67% and that of COD 69%. This method is only suitable for pre- or post-treatment of these wastewaters. Control of the treatment processes appeared to be essential for their proper functioning.
