Open-access Effect of toxicants from non-domestic wastewater on the growth of aerobic, anaerobic, and algal biomass

The present study used toxicity tests to investigate the effects of several toxicants on the growth of aerobic (activated sludge), anaerobic (sludge) (Upflow Anaerobic Sludge Blanket (UASB)), and algal (Chlorella vulgaris cultivation) biomasses. The toxicants analyzed are included in Brazilian water authorities’ regulations for the discharge of non-domestic wastewater (NDW) into sanitary sewage networks. First, the concentration ranges commonly reported as inhibitory for the three types of biomass were surveyed in the literature. Based on this survey and considering the limits established by the NDW discharge regulations in Brazil, three doses were defined for each substance, to be used in aerobic (dissolved oxygen consumption rate), anaerobic (methane production rate), and algal (cell growth rate) toxicity tests. The tests revealed that the biomasses exhibited quite variable minimum inhibitory concentrations (MIC); aerobic biomass appeared to be more tolerant (MIC in greater magnitude) than anaerobic and algal biomass, with the latter being the most sensitive. Aerobic sludge was particularly sensitive (toxicity observed at 1 mg.L-1) to lead, cobalt, total chromium, iron, zinc, and sulfide. In comparison, anaerobic sludge was more sensitive to tin and mercury (0.1 and 0.5 mg.L-1, respectively). Algal biomass was more sensitive to vanadium, cobalt, and sulfide (0.2, 0.5, and 0.5 mg.L-1, respectively). Arsenic, copper, total chromium, iron, phenols, and sulfate had minimum inhibitory doses (for all three biomasses) lower than the values proposed by some Brazilian water authorities, indicating the need for more in-depth studies on these substances to encourage future reviews of the currently established limits.

Keywords:
industrial wastewater; metals; toxic compounds; toxicity; inhibition; activated sludge; anaerobic digestion; facultative ponds

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