Microalgae culture to treat anaerobic digestion abattoir effluent (ADAE)

Current abattoir wastewater treatment options involving aerobic and anaerobic digestion systems are relatively inefficient in reducing the inorganic nutrient load (i.e. ammonium and phosphate) of the effluent. With anaerobic lagoons favoured in Australia resulting in large land footprint, loss of environmental and economic value in the form of water and nutrient recovery. The cultivation of microalgae on undiluted anaerobic digestion abattoir effluent (ADAE) offers many potential benefits such as the bioremediation of waste nutrients typically found in the effluent and simultaneous production of valuable algal biomass which represents the conversion of waste-to-profit. Microalgal culture on undiluted ADAE require minimal to no freshwater input and does not compete for arable land, it has the potential to play an important remediation role particularly during the final (tertiary) treatment phase. The generated biomass can also be a source of revenue for the targeted abattoir. To the best of my knowledge, to date, there has been no attempt on testing the growth of algae to treat undiluted ADAE. In this study, the growth, biomass productivity, photo physiology and nutrient removal rates of mono and mixed culture of Chlorella sp. and Scenedesmus sp. were evaluated in unfiltered and undiluted ADAE. Chlorella sp. showed the highest ammonium removal rate of up to 11.93±1.14 mgL-1 d-1 as well as the highest biomass productivity of 31.52±0.81 mgL-1 d-1 when compared to the other treatments. Phosphate removal rates were highest in the Scenedesmus cultures while the mixed cultures varied amongst other parameters measured (COD, Nitrite and Nitrate). Chlorella sp. with a specific growth rate of 0.260±0.047 d-1 and mixed Chlorella sp. within consortium (0.294±0.024 d-1) were the dominant species when compared to Scenedesmus sp. (0.062±0.011 d-1). Overall, Chlorella sp. was identified as the most efficient microalgal species capable of growing on undiluted ADAE with the potential to generate a waste-to-profit system