Biofuel production potential from wastewater in India by integrating anaerobic membrane reactor with algal photobioreactor

Abstract

A critical analysis of the novel sewage treatment concept of anaerobic digestion followed by CO2 capture by microalgae has been carried out, with particular reference to India. The anaerobic process would convert the sewage COD into methane and CO2, the latter being converted into microalgae in a photobioreactor process, using sunlight as an energy source. The microalgae can be used to produce biofuels, co-fired with high yielding fuels (like coke) or just recycled back into the anaerobic digestion cycle as a substrate for methane production. Overall, this process would allow, at least in principle, the conversion of all the carbon in the municipal wastewaters into fuels. This study reports data on municipal wastewater generation and treatment facilities across the globe. The focus is then given to sewage generation and treatment in Indian cities, classified into metropolitan, Class-I and Class-II cities. Aerobic and anaerobic digestion processes for sewage treatment are then compared with a discussion on the advantages of the anaerobic membrane bioreactor (AnMBR). The advantages and limitations of photobioreactors for microalgae growth are discussed. Mass balances are then carried out with reference to sewage flows and concentrations in India, and the potential energy generation from the process is estimated. Overall, the complete process is envisaged to produce about 1.69×10 8 kWhd-1 of energy from biogas and microalgae. This has the potential to replace 3% of the recent total petroleum product consumption in India. The study goes towards "zero discharge" of waste to the environment, thus representing a promising sustainable development.

India's biomethane generation potential from wastes and the corresponding greenhouse gas emissions abatement possibilities under three end use scenarios: electricity generation, cooking, and road transport applications

“…104–110 The annual state-wise sewage generation in 2018–19 was obtained from Government data. 111 The total biomethane generation volume ( V ) from a particular volume of wastewater ( W water ) is found using eqn (3): 97,112,113 V = W water × COD × Y b,COD × COD removed Here, COD is the mass of COD present per unit volume of wastewater, Y b,COD is the biomethane yield per unit mass of COD removed, and COD removed is the fraction of COD removed during anaerobic digestion.…”

“…The methane yields per unit mass of COD removed (Y b,COD ) are comparable for different anaerobic reactor models (with similar HRTs); so, the mean of various observations in the literature was used. The mean rates of COD removal (COD removed ) and methane generation are 88% 97,99-103 and 261 m 3 /tonne-COD removed 97,100,101,103 , respectively. The average COD content of sewage is 314.9 mg/L, based on multiple experimental investigations in various Indian cities [104][105][106][107][108][109][110] .…”

“…Municipal wastewaters or sewage contain organic matter, which can be treated by anaerobic digestion to produce biogas. 97 This organic content is measured by the chemical oxygen demand (COD), which is the mass of oxygen required for the decay of organic matter present in a unit volume of water. 98 Thus the "mass of COD removed" is a measure of the quantity of organic matter removed.…”

“…[104][105][106][107][108][109][110] The annual state-wise sewage generation in 2018-19 was obtained from Government data. 111 The total biomethane generation volume (V) from a particular volume of wastewater (W water ) is found using eqn (3): 97,112,113…”

Bioremediation of industrial effluents: A synergistic approach

“…The algal yield relies on the availability of CO 2 , light, nutrients, the culture density, degree and pattern of mixing of CO 2 , and nutrients. The operating conditions of the PBR can be dynamically modified according to the experimental requirements [149]. The microalgae have proved to be an advantage in treating the wastewater containing micropollutants due to their capability to thrive in austere conditions [150].…”