Abstract
There is significant potential for employing algae in tertiary wastewater treatment, however, little is known about the contribution of algae-bacteria synergy toward treatment performance. This study demonstrates potential synergy in the treatment of three winery wastewater samples. Two strains of green algae, Auxenochlorella protothecoides and Chlorella sorokiniana were tested and each removed > 90% of nitrogen, > 50% of phosphate, and 100% of acetic acid in the wastewater. Both algae strains grew significantly faster on wastewaters compared to growth on minimal media. Organic carbon in the wastewater apparently played a limited role in algal growth enhancement. When cultured on sterile-filtered wastewater, A. protothecoides increased soluble COD loadings in two of the three wastewaters and C. sorokiniana secreted an insoluble film. Culturing algae with the native wastewater microbial community negated the secretion of algal photosynthate, allowing for simultaneous reductions in COD and nutrient concentrations. Both algae species stimulated bacterial growth in a strain-specific way, suggesting unique responses to algal photosynthate. Cofactor auxotrophy for thiamine, cobalamin, and biotin is widespread among algae and these cofactors are typically obtained from bacteria. Sequencing the wastewater microbial community revealed bacteria capable of synthesizing all three cofactors while liquid chromatography with mass spectrometry (LCMS) and bio-assays revealed the presence of thiamine metabolites in the wastewaters. These cofactors likely increased algal growth rates, particularly for A. protothecoides, which cannot synthesize thiamine de-novo but can salvage it from degradation products. Collectively, these results demonstrate that bacteria and algae provided synergistic growth benefits, potentially contributing to higher levels of wastewater treatment than either organism type alone.
Highlights
Many agricultural and food processing operations are increasingly employing anaerobic digestion to reduce organic carbon loads in wastewaters while producing methane-rich biogas.[1]
When A. protothecoides was grown on sterile-filtered wastewater, soluble organic material was secreted into the wastewater as observed by the increase in chemical oxygen demand (COD) loads in the pre- and post-crush wastewaters after algae cultivation
Culturing green algae with the native wastewater community resulted in the greatest removal of both COD and nutrient pollutants from the wastewater
Summary
Many agricultural and food processing operations are increasingly employing anaerobic digestion to reduce organic carbon loads in wastewaters while producing methane-rich biogas.[1]. Numerous studies exist on the use of algae to treat various types of wastewaters including those from dairies,[7] piggeries,[8] wineries,[9] slaughterhouses,[10] and municipalities.[11,12] The fact that algae can grow successfully on such chemically diverse wastewaters indicates the potential scalability of algal wastewater treatment. Significant hurdles remain including potential negative interactions among native wastewater organisms and algae. In addition to measuring changes in water quality parameters in the present study, we investigated how green algae and native wastewater organisms interact in the treatment process. The relative contributions of algae and the native wastewater community toward the observed changes in water quality parameters were studied. 1234567890():,; Algal–bacterial synergy in treatment of winery wastewater BT Higgins et al
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