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The feasibility of Multimodal Algal-bacterial Bioprocess (MAB) for the treatment of primary clarified municipal wastewater was demonstrated at a pilot-scale MAB system (0.2 m3/d) installed and operated in Corvallis, Oregon, USA for one year. The system consisted of an anaerobic reactor; mixotrophic and phototrophic ponds followed by algal settlers and a final wetland cell (WC). The wastewater treatment performance was monitored weekly over the one-year period in terms of onsite parameters as pH, dissolved oxygen (DO), oxidation reduction potential (ORP), electrical conductivity (EC), total dissolved solids (TDS),turbidity and chemical parameters (COD, Nitrate-N, Amm.-N and reactive phosphorus). Algal biomass production and algal community analysis in the MAB was determined regularly. A continuous improvement in the mean DO (1.57–13.98 mg/L) and ORP (−140 to +86 mV) was observed throughout the study period. Higher mean pH (8.62) and DO (14 mg/L) in the ponds indicated high algal photosynthesis. The pilot-scale system maintained an average low final effluent turbidity (14.2 NTU), TSS (

Globally, treatment and management of wastewater are a serious challenge. Voluminous wastewaters are generated on a day-to-day basis that is being either partly treated or untreated finds its ways into surface and groundwater thus enriching the systems with nutrients, pollutants and pathogens. In purview of the increasing water scarcity, rapid water deterioration, higher primary productivity in surface waters due to nutrient enrichment, towering wastewater production and complications related to its treatment, the understanding of water footprint, underlying mechanisms of wastewater treatment and transformation of terrestrial nutrients into value-added products and various downstream processes for their recovery needs to be understood. In this context, the algal treatment systems not only provides a simple and economical solution to wastewater treatment but also aids in the production of many valued bio-based products like lipids as feedstock for biofuels, single-cell proteins, Omega 3 fatty acids, carotenoids as astaxanthin and β-Carotene. The present chapter throws light on various mechanisms and strategies of wastewater transformations into value-added products while evaluating the techno-economics and feasibility of such systems for assessing its potential to be a bio-based industry. Various strategies for algal species selection targeting specific wastewater pollutants grown either as natural population or as engineered consortia with numerous wastewater treatment approaches until the production of valorized biomass is being discussed. Lastly, key techno-economics, environmental challenges and the scope of wastewater transformations into bio-based products are enumerated.

Lagoons have been traditionally used in India for decentralized treatment of domestic sewage. These are cost effective as they depend mainly on natural processes without any external energy inputs. This study focuses on the treatment efficiency of algae-based sewage treatment plant (STP) of 67.65 million liters per day (MLD) capacity considering the characteristics of domestic wastewater (sewage) and functioning of the treatment plant, while attempting to understand the role of algae in the treatment. STP performance was assessed by diurnal as well as periodic investigations of key water quality parameters and algal biota. STP with a residence time of 14.3 days perform moderately, which is evident from the removal of total chemical oxygen demand (COD) (60 %), filterable COD (50 %), total biochemical oxygen demand (BOD) (82 %), and filterable BOD (70 %) as sewage travels from the inlet to the outlet. Furthermore, nitrogen content showed sharp variations with total Kjeldahl nitrogen (TKN) removal of 36 %; ammonium N (NH4-N) removal efficiency of 18 %, nitrate (NO3-N) removal efficiency of 22 %, and nitrite (NO2-N) removal efficiency of 57.8 %. The predominant algae are euglenoides (in facultative lagoons) and chlorophycean members (maturation ponds). The drastic decrease of particulates and suspended matter highlights heterotrophy of euglenoides in removing particulates.

Prolific algal growth in sewage ponds with high organic loads in the tropical regions can provide cost-effective and efficient wastewater treatment and biofuel production. This work examines the ability of Euglena sp. growing in wastewater ponds for biofuel production and treatment of wastewater. The algae were isolated from the sewage treatment plants and were tested for their nutrient removal capability. Compared to other algae, Euglena sp. showed faster growth rates with high biomass density at elevated concentrations of ammonium nitrogen (NH4-N) and organic carbon (C). Profuse growth of these species was observed in untreated wastewaters with a mean specific growth rate (mu) of 0.28 day(-1) and biomass productivities of 132 mg L-1 day(-1). The algae cultured within a short period of 8 days resulted in the 98 % removal of NH4-N, 93 % of total nitrogen 85 % of ortho-phosphate, 66 % of total phosphate and 92 % total organic carbon. Euglenoids achieved a maximum lipid content of 24.6 % (w/w) with a biomass density of 1.24 g L-1 (dry wt.). Fourier transform infrared spectra showed clear transitions in biochemical compositions with increased lipid/protein ratio at the end of the culture. Gas chromatography and mass spectrometry indicated the presence of high contents of palmitic, linolenic and linoleic acids (46, 23 and 22 %, respectively), adding to the biodiesel quality. Good lipid content (comprised quality fatty acids), efficient nutrient uptake and profuse biomass productivity make the Euglena sp. as a viable source for biofuel production in wastewaters.

Recently, algae have been realized as effective transformers of terrestrial and atmospheric carbon (C) and nitrogen (N) that help naturally mitigate greenhouse gas (GHG) emissions. Carbon and nutrients (N and P) fixation via algal route in agricultural and municipal wastewaters has been shown to be promising and can be economically transformed into high-quality by-products, such as single-cell proteins (SCPs) during the treatment. SCP production through algal pond processes only involves costs associated with algal harvesting and processing, being a by-product of the wastewater treatment process contrary to other fermentation-based SCP production processes. Unlike other cost- and energy-intensive processes, these processes are simple, scalable, and driven by solar energy that transforms wastewater nutrients into algal proteins and aids in treatment and purification. In this context, algae predominant in treatment ponds comprising euglenophycean members were isolated and checked for efficacy in SCP production as treatment by-products. Batch studies were initially performed to understand kinetics on growth rate, biomass production, and protein yield. Subsequently, field studies during different seasons were performed in Vpuram Agricultural Farm, Mysore, for estimations of algal growth, areal productivity, SCP yield, and cost economics. The results for the batch studies showed 93.3% conversion of wastewater N forms into algal proteins with a potential SCP productivity of ∼20 mg/L per day. Fourier transform infrared spectroscopy (FTIR) analysis confirmed higher protein buildup in the later stages of algal growth. The field investigations revealed high algal growth during pre-monsoon periods with an average SCP areal productivity of 25 g/m 2 per day. Cost analysis based on the field experiments showed encouraging prospects of protein biorefinery from wastewaters with cost of INR 73 (USD 1.1) for generation of a kilogram of algal SCP. The integrated value of the benefits derived from a combination of algal pond treatment processes and SCP production via subsurface concentration (harvesting) and drying provides multiple benefits, such as: (1) alternate methods for nutrient removal and wastewater treatment; (2) water saving and generation of recycled water for domestic utilities; (3) GHG emission reduction and; (4) low-cost SCP production, which significantly exceeds the estimated production costs.

The current study aims to formulate an alternative cost-effective sustainable wastewater treatment option for towns and cities in India through a comparative assessment of the treatment efficacy of mechanical treatment systems, facultative pond-based systems, and man-made lake systems based on physico-chemical and biological parameters. The key treatment parameters were analysed along with the assessment of total annual cost for operation of facultative pond and mechanical treatment systems. The results show that lake systems performed well under higher organic load with the removal efficiency of 70 % chemical oxygen demand (COD), 73 % total nitrogen (TN) and 22 % total phosphorus (TP). However, facultative pond-based systems were effective in the removal of up to 93 % suspended solid (SS) and 82 % biochemical oxygen demand (BOD). The conventional mechanical treatment removed 98 % SS, 74 % COD and 63 % BOD and is ineffective in the removal of nutrients. Furthermore, wastewater algae growing in lakes and ponds showed better lipid content (25–28 %) with suitable fatty acids (C16–C18 > 90 %). The FAME analysis showed high C16:0 (>40 %) followed by C18 fatty acids that further provides scope for algal biofuel generation to meet the regional energy demand. This necessitates an efficient algal capture mechanism to free the final treated effluent from algal BOD and solids and use of algal biomass as viable energy alternatives. Nutrient-integrated treatment efficiency (NITE) based on physical, chemical and biological factors has been devised for evaluating treatment efficiencies. Based on these efficiencies and cost of organic matter and nutrient removal for domestic wastewater treatment options, the best results were obtained for the lake and facultative algal pond-based systems which would be highly effective in Indian context and pave a way for sustainable wastewater treatment with resource recovery.

Influx of sewage into surface water results in nutrient enrichment and consequently leads to algal bloom and voluminous organic sludge production in urban areas as in case of Bangalore. The lack of utilities of algae and resulting sludge has lead to anoxia and GHG emissions. Environmental friendly ways of sludge and algal biomass utilities as well as disposal are scant. Testing for biofuel and thermal properties can be beneficial to meet the energy requirement to run treatment plants that might have better fuel value to increase the net energy gain in the system. As the volume of algal biomass and quantity of sludge has increased over the past few years, sustainable means of biomass and sludge utilization needs to be devised for beneficial purposes, to keep the surface waters clean and regulate the biomass productivity of such systems. Therefore the biomass and sludge characterization becomes imperative for any further utilities. In the present study the indigenous suspended algae and the algal bioreactor sludge were characterized for the different functionalities and presence of bio-chemicals (carbohydrates, proteins and lipids) through Infrared Analysis (ATR-FTIR). The total lipids and fatty acid methyl esters (FAME) composition were studied. The heat values and thermal decomposition pattern were analyzed by [Thermogravimetry (TGA)/Differential Thermal Analysis (DT) and Differential Scanning Calorimetry (DSC)]. The algae were found to have a better total lipid content of >34 % compared to 22% in case of wastewater sludge with quality FAME for better biofuel properties. However there were higher number of FAME in wastewater sludge (>30) where C16 and C18 members dominated. Algal biomass showed higher calorific value of 17.96 MJkg-1 compared to 10.33 MJkg-1 of wastewater sludge.

Manmade waterbodies have traditionally been used for domestic and irrigation purposes. Unplanned urbanisation and ad-hoc approaches have led to these waterbodies receiving untreated sewage. This enriches and eutrophies the waterbody. A physico-chemical and biological analysis of sewage-fed Varthur Lake in Bangalore was carried out and its treatment capabilities in terms of BOD removal, nutrient assimilation and self-remediation were assessed. Anaerobic conditions (0 mg/L) prevail at the inlet which improves towards the outlets due to algal aeration. This removed >50% BOD in the monsoon season but was inhibited by floating macrophytes in all other seasons. Alkalinity, TDS, conductivity and hardness values were higher when compared to earlier studies. This study shows the lake behaves as an anaerobic∼aerobic lagoon with a residence time of 4.8 d treating the wastewater to a considerable extent. Further research is required to optimise the system performance.