Environalgae

The most commonly regulated effluent discharge specifications that necessitate installation of customized unit operations and processes include total suspended solids (TSS), chemical oxygen demand (COD), biological oxygen demand (BOD), nitrogen (N), oil & grease (O&G) and some chosen metals that cause toxicity in the environment. COD and BOD removal can sometimes be challenging, especially with high TDS (total dissolved solids) in effluent. Microbe-assisted activated sludge processes/ trickle-bed filters are usually deployed for COD and BOD removal when dealing with effluents emanating from industrial units that handle organic compounds. However, these microbial processes are sometimes difficult to customize and stabilize. Variation in effluent composition and high TDS frequently lead to destabilization of these processes. In such cases, installing zero liquid discharge (ZLD) unit is the chosen approach for meeting the environmental regulations. The most common ZLD solution is installation of thermal processes that are poor on sustainability because the carbon emissions are substantial, let alone the high CAPEX and OPEX. Algae (microalgae) provide an interesting option for treatment of effluent streams that are rich on BOD, COD, N and most of the metals. What sets phototrophic microalgae apart from heterotrophic microorganisms like bacteria and yeasts is the fact that microalgae perform photosynthesis, while others don’t. Because they do that, microalgae do not need any significant source of food (energy) because they depend upon the sun for the same. Another decisive advantage that microalgae hold over other microorganisms is that while other microorganisms need sustained supply of air (oxygen), microalgae actually produce oxygen as they survive-grow. This oxygen proves effective in removing COD and BOD, despite of TDS values in excess of 30,000 mg/L. Generated algal biomass can provide tremendous value as an aquaculture feed or as an organic fertilizer.