Abstract

  Investigations carried out on tobacco industry wastewater showed that important sources of toxic contaminants are flavoring agents containing glycogen and alcohol, absorbable organic halogens and pesticides from tobacco leaves. Shock loading of these contaminants inhibited bacterial activity during biological treatment. Input I wastewater containing such toxic substances caused decreases in bacterial number and reduced the efficiency of the treatment plant.
Viable numbers of floc-forming, total and faecal coliform bacteria within the biological treatment unit were monitored. Mortalities in bacterial populations and low chemical oxygen demand removal efficiencies were detected when absorbable organic halogens and pesticide concentrations were above 100 and 120 mg 1-1 respectively. Short-term bioassays (using bacteria, protozoa or algae) and enrichment toxicity tests (including bacteria) performed to determine potential toxicity demonstrated that 90% mortalities in microbial populations were detected when absorbable organic halogens and pesticide concentrations were as high as 200 and 290 mg 1-1, respectively. Enrichment toxicity tests indicated whether toxic, growth limiting or stimulation conditions were present. These tests showed that sufficient nutrients can stimulate bacterial growth, and high organic halogens id pesticide concentrations and chemical to biological oxygen demand ratios may inhibit microbial growth. Furthermore, results of chemical coagulation/flocculation test experiments showed that chemical treatment is effective at reducing toxicity.

Keywords: inhibition, Biopac, enrichment, floc, coliform bacteria, protozoa