Biodiesel from wastewater: lipid production in high rate algal pond receiving disinfected effluent.

The production of different species of microalgae in consortium with other micro-organisms from wastewaters may represent an alternative process, to reduce the costs, for obtaining biofuels. The aim of this study was to evaluate the influence of pre-ultraviolet disinfection (UV) in the production of lipids from biomass produced in high rate ponds. Two high rate algal ponds were evaluated: a pond that received domestic sewage without disinfection and the other receiving domestic sewage previously disinfected by UV radiation (uvHRAP). The UV disinfection did not lead to significant differences in fatty acid profile and total lipid productivities, although it increased algal biomass concentration and productivity as well as lipid content. Moreover, the overall biomass concentrations and productivities decreased with the UV disinfection, mostly as a consequence of a loss in bacterial load. We thus conclude that uvHRAP disinfection may represent a potential strategy to promote the cleaner and safer growth of algal biomass when cultivated in consortium with other micro-organisms. Mainly regarding the use of wastewater as culture medium, together with a cheaper production of lipids for biodiesel, pre-disinfection may represent an advance since extraction costs could be significantly trimmed due to the increase in lipid content.

Algal biomass production and wastewater treatment in high rate algal ponds receiving disinfected effluent.

Algal biomass production associated with wastewater is usually carried out in high rate algal ponds (HRAPs), which are concomitantly used in the treatment of such effluent. However, most types of wastewater have high levels of bacteria that can inhibit the growth of algal biomass by competing for space and nutrients. The objective of this study was to assess the influence of ultraviolet (UV) pre-disinfection on the performance of HRAPs used for wastewater treatment and algal biomass production. Two HRAPs were tested: one received effluent from an upflow anaerobic sludge blanket (UASB) reactor- HRAP -and the second received UASB effluent pre-disinfected by UV radiation-(UV)HRAP. Physical, chemical and microbiological parameters were monitored, as well as algal biomass productivity and daily pH and dissolved oxygen (DO) variation. The (UV)HRAP presented highest DO and pH values, as well as greater percentage of chlorophyll a in the biomass, which indicates greater algal biomass productivity. The average percentages of chlorophyll a found in the biomass obtained from the HRAP and the (UV)HRAP were 0.95 +/- 0.65% and 1.58 +/- 0.65%, respectively. However, total biomass productivity was greater in the HRAP (11.4 gVSSm(-2) day(-1)) compared with the (UV)HRAP (9.3 gVSSm(-2) day(-1)). Mean pH values were 7.7 +/- 0.7 in the HRAP and 8.1 +/- 1.0 in the (UV)HRAP, and mean values of DO percent saturation were 87 +/- 26% and 112 +/- 31% for the HRAP and the (UV)HRAP, respectively. Despite these differences, removal efficiencies of organic carbon, chemical oxygen demand, ammoniacal nitrogen and soluble phosphorus were statistically equal at the 5% significance level.