ALGAE BIOMASS CULTIVATION WITH AMMONIUM RICH WASTEWATERS AS SUBSTRATE : THE POTENTIAL FOR SIMULTANEOUS WASTEWATER TREATMENT AND ENERGY RECOVERY

Ammonia rich wastewaters pose risk to recipient waters and the atmosphere, and can be difficult to treat in wastewater treatment plants (WTTP) due to toxicity to the microbes in conventional biological treatment systems. This article presents an idea on how to use a combination of bacteria and microalgae for efficient treatment of wastewaters with high ammonia concentrations (200-1400 mg/L). The challenge in this research is that most algae species are sensitive to high ammonia concentrations (>1 mM)(Abalde and Mezzamo, 2009). Despite the numerous wastewaters that contain high ammonia concentrations, i.e. landfill leachate, piggery manure, reject water and biogas digestate, the progress in finding sustainable treatment methods is taking time. This despite the fact that climate change, eutrophication and eco-toxicity is negatively affected by this commonly occurring component. Further, nitrogen is a valuable nutrient that in conventional WWTP is just released into the air without any recycling or recovery.In this article, we present a study where algae were cultivated as a mean for treatment of wastewater reject water and swine manure from a piggery farm. The algae inoculum was pretreated from lake water, sampled in mid Sweden during summer algae blooms. Lake Malaren is a shallow lake with a rich algae consortia, optimized for the local climate. During seasonal algae blooms, the lake demonstrates the extremely rapid growth rate of the algae such as cyanobacteria, green algae and diatoms. Algae inoculum, wastewater substrate and dilution media (tap water) were mixed in various ranges of ammonium concentrations to evaluate the nutrient removal and algae biomass growth. During the algae cultivation experiment, chlorophyll, optical density and TS were used as indicators for algae biomass growth. Flow Injection System (FIA) was used for nutrient analysis.The two main findings in this research are that algae growth is inhibited by ammonia but that it is possible to grow algae in readily high ammonia concentrations. Moreover, significant amount of ammonium were removed by algae during the cultivation in the reactors.