Phycoremediation of wastewater by Chlorella pyrenoidosa and utilization of its biomass for biogas production

Abstract

This study aims to focus on simultaneous wastewater treatment and clean energy production using Chlorella pyrenoidosa (C. Pyrenoidosa) microalgae. The growth of C. Pyrenoidosa is performed in real sewage treatment plant wastewater (STPW) and synthetic wastewater (SWW). During its growth the C. Pyrenoidosa, reduces the nitrate, phosphate and chemical oxygen demand (COD) as 99.2%, 70.1%, and 61.0%, respectively from SWW; for STPW these values are 99.5%, 94.2%, and 87.1%, respectively. The growth of C. Pyrenoidosa is studied in terms of algal biomass generation and used for biogas production by anaerobic digestion in the presence of anaerobic microorganisms. The pretreatment methods such as thermal (temperature 900 °C, time 8 h), hydrothermal (temperature 121 °C, pressure 15 psi, time 15 min), ultrasonic (power 100 W, time 15 min) and Fenton (speed 140 rpm, time 3 h) are used for pretreatment of algal biomass to enhance the biogas production. Total biogas yield of 479 mL and methane yield of 147 mL/volatile solid (g) are obtained from untreated algal biomass. Ultrasonic, thermal, hydrothermal and Fenton pretreated microalgae biomass show 15.5%, 8.2%, 18.4% and 10.9% enhancement in methane production, respectively; while for total biogas production, the corresponding values are 7.93%, 10.43%, 14.19% and 11.06%, respectively.