EFFECT OF BTX ON BIOLOGICAL PHOSPHORUS REMOVAL

Abstract

Biological phosphorus removal is becoming a. necessity to meet out environmental regulations for phosphorus discharge into water course. It is a two step process involving anaerobic phosphorus release followed by aerobic phosphorus uptake. Toxicants entering wastewater from different source are likely to affect biological phosphorus removal. The present work emphasises the effect of BTX compounds viz benzene, toluene and xylene on anaerobic release and aerobic uptake of phosphorus. BTX have contaminated soil, groundwater and wastewaters through the processing, handling and storage of gasoline and aromatic solvents. Since in actual situation possibility of presence of two or three of the BTX compounds is more than that of individual compounds, the study was conducted with various mixed doses of toxicants. Investigations were carried out in two phases. In the first phase a 51 SBR maintained at 22°C was operated through a cyclic operation of 6 h to cultivate bio-P sludge. The sequence followed in each cycle was 8 minutes fill, 87 minutes anaerobic, 160 minutes aerobic, 77 minutes settle, 3 minutes decant and 25 minutes idle period. In the second phase, the toxicity response of bio-P sludge to mixed doses of BTX was evaluated in 500 ml serum bottles. A complete test of. one chemical involved the observation of phosphorus concentration variation over a period of six hour cycle which comprised of 2 hour anaerobic period followed by a 4 hour aerobic period. The phosphorus release and uptake was monitored at each concentration of the various mixed doses of BTX. Various mixed doses of benzene (0-440 mg/I) and toluene (0-130 mg/I), benzene (0-550 mg/I) and xylene (0-1101 mg/I), toluene (0-152 mg/1) and xylene (0-1101 mg/I) and benzene (0-440 mg/I); toluene (0-130 mg/1) and xylene (0-881 mg/1) were studied and the results showed that if we take maximum phosphorus release as guiding value there is an increase in anaerobic phosphorus release with increasing doses of toxicants however the effect were not quite conspicuous. But the aerobic phosphorus uptake was found to be significantly decreasing with the increasing amount of mixed doses of toxicants.