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Cornstarch industry generates a huge amount of acidic effluent, that is, 5–11 M3/Mt grinding, with a high load of chemical oxygen demand, 6000–19000 mg/L. The acidic effluent requires neutralization making the treatment process expensive. Methanogenesis under the acidic environment (pH 5–5.5) can reduce the cost of operation as well as treatment time. This research focuses on the evaluation of the optimum condition of COD reduction and methane generation simultaneously from leaf debris sludge using Box–Behnken model. Three 1 L bioreactors were seeded with 5000–10000 mg/L inoculum and operated at different pH 4.0–7.0 for 72 hr up to 10 cycles. The production of methane was found maximum 2980 ml after treating the wastewater from the starch industry at pH 5.57 and 9612.9 mg biomass load at 62.4 hr. The high reduction rate of around 97% shows there is ample opportunity for further research on low pH treatment of waste along with recovery as methane. Practitioner points The low pH tolerant methanogenic bacteria are promising and are isolable from various natural resources. The low pH tolerant methanogens was able to remove 97% COD from starch industry effluent at pH 5.57. The recovery of methane was 2980 ml from 9612 mg/L COD which is at per with present treatment system thus provides cost effective alternatives.

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Microflora from leaf debris is suitable for treatment of starch industry wastewaterBiological treatment of industrial waste is a widely practiced technique that generates comparatively less environmentally hazardous waste than other chemical treatment processes. Wet milling of maize generates huge amount of wastewater (5 m 3 /ton) of low pH with organic matter and nutrients. Anaerobic methanogenic and aerobic bacteria are mostly highly sensitive to low pH. The treatment of wastewater causes huge cost of chemical neutralization or hydraulic recirculation for maintaining neutral pH. In the present study, different microbial consortia isolated from cow dung, active sludge from an anaerobic reactor for treatment of industrial wastewater, and leaf debris from benthic soil were screened for tolerance against low pH and for potential of chemical oxygen demand (COD) removal in order to find out an alternative microbial population for industrial water treatment at low pH. The most effective consortia found from leaf debris were further investigated for optimal operation. The microscopic analysis of leaf debris sludge showed abundance of Gram-negative methanococci, which was found tolerant to low pH in plate culture method. On further investigation for COD removal from starch industry effluent, they were found to be most effective at pH 5 with highest COD removal rate of 70% and lowest biomass generation of 81%. Hence, it was concluded that the low pHtolerant methanogen bacteria, enriched from leaf debris sludge, is highly beneficial for anaerobic treatment of wastewater from several industries including corn starch industry by reducing cost of operation for neutralization to neutral pH and through reducing excess waste sludge production by the treatment system.

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