Nutrient status of wastewater in a fertilizer-factory-waste discharge equalization basin

The characteristics of wastewaters from a fertilizer factory, producing NH3, urea, diammonium phosphate (DAP) and nitrogen-phosphorus-potassium (N-P-K) fertilizer blends, were monitored in stages for 18 months to correspond with the various stages of production of the different fertilizer minerals. Analysis of physico-chemical parameters of the various wastewater categories gave the following results: temperature, 28•0–32•5°C; pH, 5•0–9•48; conductivity, 2•5–2900•0 μmhos/cm; turbidity, 2•8–17•0 NTU; colour, 5–45 platinum cobalt units; DO, 1•4–7•0 mg/l; BOD5, 1•0–41•4 mg/l; TS, 1000–8640 mg/l; TDS, 800–7600 mg/l; TSS, 200–3480 mg/l; acidity, 3•0–1000•0 mgCaCO3/l; alkalinity, 10–460 mgCaCO3/l; chloride, 249–1779 mg/l; total hardness, 0•0–20•0 mgCaCO3/l; salinity, 0•0–3•5‰; calcium, 0•0–18•0 mg/l; magnesium, 0•0–0•972 mg/l; potassium, 18•0–50•0 mg/l; sulphate, 0•0–6640 mg/l; orthophosphate, 5•0–64•0 mg/l; NO3-N, 0•04–1•57 mg/l; NO2-N, 0•0–0•09 μg/l; NH3-N, 0•0–0•72 mg/l. Variable results were obtained for the total coliform and faecal coliform counts with a range from 0 to > 1100 MPN/100 ml. Culturable aerobic heterotrophic bacteria populations ranged from 0•53 to 3100 × 103 cfu/ml. The fluctuations in these parameters were attributed to seasonal variations, varying effluent volumes, due to increased production capacity of the fertilizer plant, and the type of fertilizer mineral produced. A review of the waste-treatment system in the fertilizer factory is suggested, in order to minimize the impact of the pollutant components of the effluents on the ecology of the receiving creek.