A new energy-positive technological approach for wastewater treatment and bioenergy generation using a photo\xa0anoxic baffled reactor (PABR)

M Hasan,S B Kabir,P Datta,M Alamgir,Md Khalekuzzaman

doi:10.1007/s13762-021-03168-7

Abstract

This study proposed a new energy-positive technological approach for wastewater treatment and bioenergy generation using an algal–bacterial symbiosis system in a photo anoxic baffled reactor (PABR). The PABR consisted of a sedimentation chamber, four regular baffled chambers, and two floated filter media chambers. The PABR was operated in the presence of natural sunlight with an average intensity of 30 µmoles/m2/s. A wide range of ORP (−215 to 255 mV) data suggested that a suitable environment condition existed in the PABR for photosynthesis, nitrification, and denitrification. Simultaneous nitrification/denitrification (SND) was observed in the first three chambers, and microbial assimilation was governed in the last four chambers. An average biochemical oxygen demand (BOD), NH3–N, total nitrogen (TN), and PO43− removal efficiencies were more than 88, 48, 36, and 42%, respectively. Moreover, hydrothermal liquefaction (HTL) was carried out for sludge and microalgae samples for bioenergy (e.g., biocrude and biochar) conversion, where the sludge sample containing microalgae and bacteria was collected from PABR and microalgae sample was collected from photobioreactor. Finally, the Fourier transform infrared spectroscopy (FTIR) analysis was done for both biocrude and biochar derived from sludge and microalgae samples, and it was suggested that the biocrude and biochar derived from sludge sample were better than that of microalgae sample.

Highlights

As Bangladesh is located in the subtropical/tropical region with a warm climate (15–35 °C), the biological wastewater treatment process would be the best option for wastewater management
This study investigated the combined effect of microalgae–bacteria consortium in removing nutrient and organic matter from domestic wastewater
The oxygen redox potential (ORP) values indicated that the reactor was automatically divided into two unit systems that generally consist of an anoxic zone and aerobic zone due to the unique compartmentalized structure of the photo anoxic baffled reactor (PABR)

Summary

Introduction

As Bangladesh is located in the subtropical/tropical region with a warm climate (15–35 °C), the biological wastewater treatment process would be the best option for wastewater management. The anaerobic processes of wastewater treatment have been gained special attention among the researchers due to economic and environmental benefits over conventional aerobic treatment (Khalekuzzaman et al 2019). Among all high-rate anaerobic reactors, the anaerobic baffled reactor (ABR) is extensively used in treating wastewater. It was developed by McCarty and co-workers at Stanford University, and it can be described as a series of up-flow anaerobic sludge blanket reactors (UASBs) (Rongrong et al 2010). The other advantages are no special arrangement for gas and sludge separation, lower sludge yields, longer biomass retention times (SRT), lower hydraulic retention time (HRT), and its ability to separate

Methods

Results

Conclusion