Microalgae cultivation in wastewater is an emerging approach to remove its contaminants and generate microalgal biomass. This study aimed to screen and isolate potential strains in a cassava biogas effluent wastewater (CBEW) treatment system and produce algal biomass. Chlorella sorokiniana strains P21 and WB1DG were isolated from CBEW and found to grow by utilizing various carbon sources. Experiments conducted in a batch reactor using an unsterilized substrate were done to evaluate the nutrient removal and growth of isolated strains from CBEW. The results showed that C. sorokiniana P21 and WB1DG could achieve biomass accumulation of more than 2564 and 1301 mg L⁻¹, respectively. The removal efficiencies of chemical oxygen demand (COD), total phosphorous (TP), and total inorganic nitrogen (TIN) were found up to be 63.42, 91.68, and 70.66%, respectively, in a WB1DG culture and 73.78, 92.11, and 67.33%, respectively, in a P21 culture. Harvestability of the P21 strain was examined using several coagulant–flocculants. FeCl₃ was found to remove more than 90% of the cells. Nutrient removal and growth rates resulting from these indigenous strains with application of untreated CBEW support the possibility of this strain being a promising candidate to couple a CBEW treatment and algal biomass generation with minimal process adjustment.

The development of microalgae cultivation in wastewater has been explored for years. Several wastewaters and nutrient sources related to biomass generation have been combined in recent years. On the other hand, several factors seem to reduce the possibility of industrialized this concept shortly. The growth rate and harvesting cost of the algae are often pointed as the leading cause of the gap for industrialization of this concept. In order to counteract these problems, constructing microalgae in the form of co-culture consortia with microorganisms, such as bacteria and yeast, have been reported to enhance the production of biomass under a short period of cultivation. This review highlights the strategies to combine microbial strains and microalgae for improving the process of biomass generation based on the comparison of the productivity of single and consortium of microalgae cultivation. Subsequently, mechanisms to enhance microalgae growth are scrutinized based on their interaction. Furthermore, critical factors regarding the construction of the consortia are discussed. Eventually, identifying gaps in this concept is displayed to describe the path of future focuses in this potential field.

Pretreatments of pH and heat with zero-valent iron (ZVI) additions enhance anaerobic digestion and increase reducing sugar availability for optimum biogas production. This study aimed to optimize the conditions of different pH and heat pretreatment with additional ZVI to yield higher biogas amounts from the anaerobic digestion (AD) of cassava wastewater. Thirteen pH conditions, ten ZVI concentrations, and eleven heating periods were varied and measured to optimize the standard conditions. Four mathematical models that are widely used to evaluate the cumulative biogas production were employed, namely, the Modified Gompertz, Logistic, Transference, and Exponential models. The pretreatment of pH 10 and 35 min of boiling time with a ZVI concentration of 60 g·kg·TVS⁻¹ produced the highest cumulative biogas at the end of the AD process. The Logistic and Modified Gompertz models were better fitted with the experimental data than the other models. Interestingly, the optimized conditions altered the biogas production rate but prolonged the lag phase. A reasonably positive correlation was also found between the FeOOH amount and biogas production rate in the LF and MG models. These optimal fitted models, kinetics parameters, and possible correlations are novel findings that can help develop extensive scale developments for biogas generation from cassava wastewater.

Combining microalgae cultivation with nutrient removal is a promising technique as it enables renewable energy generation with the additional potential removal of wastewater contaminants in a single process. Performance and total yield of this process are still below the standard for industrialization. Thus, optimization is needed to reach the feasibility and actualize the concept. Cultivation conditions and reactor design play essential roles in the application and feasibility of this process. Both aspects have been developed through the years to enable the industrial application of this concept. Cultivation conditions are usually categorized into trophic conditions in which each situation has its specific function and target of removal. These conditions, however, are also applied in various reactor systems. Closed photobioreactor and open pond are two central systems for the reactor. Two of the most applied reactor models in wastewater are reviewed here to create a broad picture of the algae cultivation process by emphasizing biomass production and considering different aspects.