Nutrient Removal by Suspended and Biofilm Microalgae for Treating the Wastewater of Agro-Industrial Pig Farm

In this study, laboratory-scale suspended and biofilm microalgal systems were constructed under outdoor climatic conditions in Northern Thailand to compare their performances on nutrient nitrogen (N) and phosphorus (P) removal and biomass production from anaerobically digested piggery wastewater. At a cultivation time of 14 days, the results showed that removal efficiencies of nitrogen and phosphorus from digested piggery wastewater in biofilm microalgal system were higher than suspended microalgal system. Biofilm system removed on average of 96 % of TKN-N and 92 % of PO43--P, whereas suspended system removed on average of 84 % of TKN-N and 87 % of PO43--P. Average biomass production achieved 1.17 g dry weight/day for suspended system, while a lower production of 0.78 g dry weight/day was found for biofilm system in which possibly due to a long harvesting frequency of every 2-weeks. Meanwhile, biofilm system has an advantage over suspended system with respect to simple biomass harvesting. This combination of findings demonstrates that biofilm microalgal system is more suitable for removing N and P from digested piggery wastewater than suspended microalgal system. Besides, biomass production in biofilm microalgal system could be further optimized by shorter harvesting frequency and partially harvesting of the biofilm biomass. This study indicates that microalgae offer the potential to recover valuable nutrient resources from piggery wastewater and use biomass for sustainable energy production or other high-value products, which will improve sustainability of agro-industrial wastewater management in the future.