Biological Approaches Integrating Algae and Bacteria for the Degradation of Wastewater Contaminants—A Review

Abstract

The traditional approach for biodegradation of organic matter in sewage treatment used a consortium of bacterial spp. that produce untreated or partially treated inorganic contaminants resulting in large amounts of poor-quality sludge. The aeration process of activated sludge treatment requires high energy. So, a sustainable technique for sewage treatment that could produce less amount of sludge and less energy demanding is required for various developed and developing countries. This led to research into using microalgae for wastewater treatment as they reduce concentrations of nutrients like inorganic nitrates and phosphates from the sewage water, hence reducing the associated chemical oxygen demand (COD). The presence of microalgae removes nutrient concentration in water resulting in reduction of chemical oxygen demand (COD) and toxic heavy metals like Al, Ni, and Cu. Their growth also offers opportunity to produce biofuels and bioproducts from algal biomass. To optimize use of microalgae, technologies like high-rate algal ponds (HRAPs) have been developed, that typically use 22% of the electricity used in Sequencing Batch Reactors for activated sludge treatment with added economic and environmental benefits like reduced comparative operation cost per cubic meter, mitigate global warming, and eutrophication potentials. The addition of suitable bacterial species may further enhance the treatment potential in the wastewater medium as the inorganic nutrients are assimilated into the algal biomass, while the organic nutrients are utilized by bacteria. Further, the mutual exchange of CO2 and O2 between the algae and the bacteria helps in enhancing the photosynthetic activity of algae and oxidation by bacteria leading to a higher overall nutrient removal efficiency. Even negative interactions between algae and bacteria mediated by various secondary metabolites (phycotoxins) have proven beneficial as it controls the algal bloom in the eutrophic water bodies. Herein, we attempt to review various opportunities and limitations of using a combination of microalgae and bacteria in wastewater treatment method toward cost effective, eco-friendly, and sustainable method of sewage treatment.

A revolving algae biofilm based photosynthetic microbial fuel cell for simultaneous energy recovery, pollutants removal, and algae production

“…The biomass of the algae biofilm with was higher than that reported in a study using domestic sewage as the cultivation medium ( Gross et al, 2013 ) and another study using polyacrylamide in simulating oil flooding wastewater as N resource ( Zhang et al, 2021 ). The concentration of nitrogen in water directly affects the growth of algal biofilm ( Lin et al, 2013 ; Mathew et al, 2022 ).…”

Evaluation of Euglena gracilis 815 as a New Candidate for Biodiesel Production

“…In the present study, however, no significant difference was observed across conditions of E. gracilis 815 in biomass accumulation by Day 6, indicating that this new strain shows strong adaptability to environmental conditions when biomass is harvested in the short term. Since we have proved the possibility of water reuse in the cultivation of E. gracilis Z recently (Wu et al, 2021a), further evaluations in E. gracilis 815 could be expanded to reusing the wastes from other process, such as exhaust gases or wastewater from factories or livestock, in the cultivation of microalgae (Tsolcha et al, 2018;Amenorfenyo et al, 2019;Dębowski et al, 2020b;Geremia et al, 2021;Mathew et al, 2021;Cheng et al, 2022;Lopez-Sanchez et al, 2022;Singh and Singh, 2022). The biomass of various E. gracilis 815 groups ranged between 0.78-0.94 g/L when their cell density ranged between 1.90 × 10 6 -2.3 × 10 6 cells/ml.…”

Phyco-Remediation of Sewage Wastewater by Microalgae

“…The activated sludge treatment microalgae facilitate nitrification by generating a sufficient quantity of dissolved O 2 [51]. The integration of a bacterial-microalgal approach for wastewater treatment is a promising approach as heterotrophic bacteria degrade the organic matter in the absence of aerated oxygen, as the microalgae provide O 2 , and similarly, the need for CO 2 sparging is eliminated as bacterial respiration produces it [52].…”