Search

Two conventional chemical coagulants (FeCl3 and Fe2(SO4)3) and five commercial polymeric flocculants (Drewfloc 447, Flocudex CS/5000, Flocusol CM/78, Chemifloc CV/300 and Chitosan) were comparatively evaluated for their ability to remove algal-bacterial biomass from the effluent of a photosynthetically oxygenated piggery wastewater biodegradation process. Chlorella sorokiniana, Scenedesmus obliquus, Chlorococcum sp. and a wild type Chlorella, in symbiosis with a bacterial consortium, were used as model algal-bacterial consortia. While the highest biomass removals (66-98%) for the ferric salts were achieved at concentrations of 150-250 mg L(-1), dosages of 25-50 mg L(-1) were required for the polymer flocculants to support comparable removal efficiencies. Process efficiency declined when the polymer flocculant was overdosed. Biomass concentration did not show a significant impact on flocculation within the concentration range tested. The high flocculant requirements herein recorded might be due to the competition of colloidal organic for the flocculants and the stationary phase conditions of biomass., (Copyright © 2010 Elsevier Ltd. All rights reserved.)

The biodegradation potential of an innovative enclosed tubular biofilm photobioreactor inoculated with a Chlorella sorokiniana strain and an acclimated activated sludge consortium was evaluated under continuous illumination and increasing pretreated (centrifuged) swine slurry loading rates. This photobioreactor configuration provided simultaneous and efficient carbon, nitrogen, and phosphorous treatment in a single-stage process at sustained nitrogen and phosphorous removals efficiencies ranging from 94% to 100% and 70–90%, respectively. Maximum total organic carbon (TOC), NH4 +, and PO4 3− removal rates of 80 ± 5 g C mr −3 day−1, 89 ± 5 g N mr −3 day−1, and 13 ± 3 g P mr −3 day−1, respectively, were recorded at the highest swine slurry loadings (TOC of 1,247 ± 62 mg L−1, N–NH4 + concentrations. In addition, this biofilm-based photobioreactor supported efficient biomass retention (>92% of the biomass generated during the pretreated swine slurry biodegradation). [ABSTRACT FROM AUTHOR]−1, P–PO4 3+ of 117 ± 19 mg L−1, and 7 days of hydraulic retention time). The unusual substrates diffusional pathways established within the phototrophic biofilm (photosynthetic O2 and TOC/NH4 + diffusing from opposite sides of the biofilm) allowed both the occurrence of a simultaneous denitrification/nitrification process at the highest swine slurry loading rate and the protection of microalgae from any potential inhibitory effect mediated by the combination of high pH and high NH3 concentrations. In addition, this biofilm-based photobioreactor supported efficient biomass retention (>92% of the biomass generated during the pretreated swine slurry biodegradation). [ABSTRACT FROM AUTHOR]

Abstract: The influence of flue gas sparging (7% CO2) on the performance of two 465L High-Rate Algal Ponds (HRAPs) treating diluted swine manure at 10 days of hydraulic retention time was evaluated under continental climatic conditions (Castilla y León, Spain). COD, NH4 +, and PO4 3− removal efficiencies were not significantly affected by flue gas input (at 2.2 and 5.5Lmin−1), which suggests that CO2 sparging does not compromise wastewater treatment in HRAPs. In this particular study, COD and NH4 + removal efficiencies of 56±31% (near to maximum swine manure biodegradability) and 98±1%, respectively, were consistently maintained, regardless of the environmental and operational conditions. CO2 sparging resulted however in lower pH values (≈2 units lower) and an enhanced NH4 + nitrification (higher NO3 − and NO2 − concentrations) compared to the system operated in the absence of flue gas supply. Biomass concentration was only higher (≈30% than in the control HRAP) when flue gases were supplied at 5.5Lmin−1, probably due to the fact that the higher irradiances and temperatures prevailing within this experimental period resulted in an inorganic carbon-limited scenario in the control HRAP. Therefore, it can be concluded that CO2 assimilation would be ultimately dependent on the occurrence of inorganic carbon limitation and will never occur in light, COD or nutrients-limited scenarios. [Copyright &y& Elsevier]