The treatability of organic synthesis industry wastewater using aerobic suspended biomass systems was studied. The wastewater had a high COD, 27–60 g/l, and low TSS, less than 200 mg/l. The organic matter was made up of alcohols, amines, ketones and aromatic compounds. Some toxic organics were present, such as toluene, up to 700 mg/l, and phenol, up to 170 mg/l. Nitrogen was present at a concentration of 200–1,900 mg/l as TKN and phosphates at 0.1 to 4 mg/l. Kinetic coefficients and design parameters obtained from bench-scale tests were used to construct pilot-scale continuous and batch bioreactors. Results from the pilot plant study showed that a removal of more than 99% can be obtained. The operating parameters for the biodegradation system applicable to this kind of wastewater are specific and depend on its strength. Using continuous feed system, efficiencies above 99% can be obtained with organic loads of 0.20–0.38 gCOD/gMLVSS/d and an HRT of 13–23 d. With greater loads and influent COD concentrations from 36,000 to 42,000 mg/l, the efficiency declines to 98%. Loads above 0.34 gCOD/gMLVSS/d and influent CODs above 34,000 mg/l inhibit biomass growth. The efficacy of the batch process is similar to that of the continuous feed system. In spite of the flexibility of the system's response to variations in the influent COD concentration, the SBR is not recommended for the treatment of the study wastewater because of the deficient sedimentability of the biomass formed during the process. The capacity of the SBR system was considerably reduced when the wastewater had a COD above 60,000 mg/l. Toxicity was observed at loads exceeding 0.25 gCOD/gMLVSS/d even with a long HRT of 47–50 d.

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