Algal-based, single-step treatment of urban wastewaters

Abstract

Currently, urban wastewaters (UWW) laden with organic carbon (BOD) and nutrients (ammoniacal nitrogen, N, and phosphates, P) are treated in multi-stage, energy-intensive process trains to meet the mandated discharge standards. This study presents a single-step process based on mixotrophic metabolism for simultaneous removal of carbon and nutrients from UWWs. The proposed system is designed specifically for hot, arid environments utilizing an acidophilic, thermotolerant algal species, Galdieria sulphuraria, and an enclosed photobioreactor to limit evaporation. Removal rates of BOD, N, and P recorded in this study (14.93, 7.23, and 1.38 mg L(-1) d(-1), respectively) are comparable to literature reports. These results confirm that the mixotrophic system can reduce the energy costs associated with oxygen supply in current UWW treatment systems, and has the potential to generate more energy-rich biomass for net energy extraction from UWW.

Optimizing energy yields from nutrient recycling using sequential hydrothermal liquefaction with Galdieria sulphuraria

“…Furthermore, this strain grows at low pH where fewer heterotrophs survive to compete for carbohydrate and organic nitrogen sources. We have previously documented the utility of this strain for direct, one-step, energy-efficient municipal wastewater treatment defraying the cost of nutrients for algal feedstock production [16][17][18][19]. We and others have noted the synergy between algal WWT and HTL energy extraction [14].…”

Maximizing recovery of energy and nutrients from urban wastewaters

“…When biomass is cultivated in UWW, a fundamental consideration to maximize biomass density is matching the C:N:P ratio of the biomass to that in UWW. While the C:N:P ratio in algal biomass is closer to that of UWW than in traditional activated sludge biomass, recycling of carbon and nutrients solubilized in the HTL process to the cultivation step as envisioned in the POWER system provides for optimal balancing of C:N:P ratio to maximize biomass productivity and hence the energy yield [33][34][35]. The POWER system thus enables removal of organic C, N, and P from UWW in a single step whereas, the traditional wastewater treatment approach involves two steps-activated sludge for organic carbon removal followed by nitrification/denitrification for N removal with supplemental carbon input to balance the C:N:P ratio between UWW and biomass.…”

Using MinION nanopore sequencing to generate ade novoeukaryotic draft genome: preliminary physiological and genomic description of the extremophilic red algaGaldieria sulphurariastrain SAG 107.79

“…These species are metabolic workhorses. Efforts have been made to harness these abilities and develop Galdieria for industrial biotechnological applications (Graziani, Schiavo et al 2013, Henkanatte-Gedera, Selvaratnam et al 2015, Minoda, Sawada et al 2015, Selvaratnam, Pegallapati et al 2015, Ju, Igarashi et al 2016. Specific goals will undoubtedly include identifying those strains best capable of using waste from the food industry and biofuel community, and assess the nature of metabolic conversions, including metal concentration bioaccumulation or bioabsorption, to determine the utility and benefit of resultant useful products.…”

“…Additionally, perhaps as acidic environments increase the solubility of most cations, G. sulphuraria bioaccumulates numerous rare-earth metals and several precious metals (Minoda, Sawada et al 2015, Ju, Igarashi et al 2016. In this versatile growth state, interest in this organism has been seen in the industrial biotechnology sector, both for remediation of wastes and in the production of high value chemicals (Schmidt, Wiebe et al 2005, Selvaratnam, Pegallapati et al 2014, Henkanatte-Gedera, Selvaratnam et al 2015, Selvaratnam, Pegallapati et al 2015, Henkanatte-Gedera, Selvaratnam et al 2016.…”