Feasibility of algal systems for sustainable wastewater treatment

Abstract

This paper proposes cultivation of algae in urban wastewaters as a sustainable approach for removing the nutrients from the wastewaters and generating energy from the biomass. The theoretical rationale of this proposal is that, the algal systems can produce nearly double the biomass per unit nutrient intake than bacterial systems and can generate nearly 20% more net energy. Preliminary experimental results are presented to demonstrate that a thermotolerant and acidophilic algal strain evaluated in this study-Galdieria sulphuraria, can grow well in primary settled urban wastewaters and can reduce nutrient levels to regulatory discharge levels at reasonable rates. Nutrient removal rates found in this study (4.70 to 5.0 mg L-1 d-1 of nitrogen and 1.5 to 1.7 mg L-1 d-1 of phosphate) are comparable to those by traditional methods.

Algal Cultivation for Treating Wastewater in African Developing Countries: A Review

“…For example, removal of 1 kg BOD from a typical activated sludge process produces 0.45 kg of waste biomass which disposal requires 50% of the plant operation cost. [ 59 ]…”

“…For example, removal of 1 kg BOD from a typical activated sludge process produces 0.45 kg of waste biomass which disposal requires 50% of the plant operation cost. [59] AD systems constitute a sustainable and environmentally friendly process for the remediation of different wastewater sources recovering the internal energy of wastewater in the form of biogas. [38] For instance, more than 17 376 AD units producing biogas which generates 60.6 trillion Watts of electricity on an hourly basis are in Europe alone in late 2015.…”

Modeling and Optimization of Algae Growth

“…They used thermo-tolerant and acidophilic algal strain (5572) of Galdieria sulphuraria, to generate algal growth and nutrient consumption data over the span of 10 days. 17,22 Fitting a model to data requires an optimizer, for which there are many good choices. Leapfrogging 23 is a recently developed heuristic, multiplayer optimization technique which relocates the worst trial solution (player), by leaping the worst over the best into a random spot in the reflected decision variable hypervolume.…”

“…The modeled temperature, initial concentrations, and pH are the same as the experimental setup. 17 The comparison of measured and modeled values of biomass, N source, and P source concentration are shown in Figure 3. The modeled biomass concentration matches the experimental data better than the other two variables because of the values of Lagrange multipliers chosen here to represent data certainty (effectively the reciprocal of the square of the standard deviation of the experimental data).…”

Algal-based, single-step treatment of urban wastewaters

“…Previous studies by the authors (Selvaratnam et al, 2014a(Selvaratnam et al, , 2014b have documented the feasibility of a thermo-tolerant, acidophilic, heterotrophic/photoautotrophic alga, Galdieria sulphuraria (here after G. sulphuraria) as a successful and robust algal species for efficient N and P removal. The choice of G. sulphuraria in this study was motivated by its metabolic versatility that includes the ability to grow on the largest known range of organic substrates known among photosynthetic microorganism (Schonknecht et al, 2013).…”