Author: Megan Hawley
Hawley, Megan, 2019 Advanced Integrated Treatment of Pig Slurry for Algal Biomass Production and Improved Pig Health, Flinders University, College of Science and Engineering
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Deriving renewable energy from pig effluent pre-treated in an anaerobic pond and through the production of algal biomass on this waste is a strategy currently being explored by the Australian pork industry. The objective to lower the environmental impacts and greenhouse gas emissions associated with pork production. Unfortunately, unfavourable concentrations of ammonia (NH3) and suspended solids (SS) obtain in pig slurry; both can have a toxic and inhibitory effect on pig and algal growth, in high dosages. Additional treatment (post) of the anaerobic pig slurry (ANPS) is advised prior to reuse
Integrated wastewater treatments for combined algal biomass and quality water production are not a new technology; however, there is still a lack of documentation available regarding the aeration of ANPS pertaining to system characterisation and algal production. The development of an enabling technology to facilitate algal growth on ANPS via the oxidation of ammonia to nitrate was examined at a laboratory scale in a low energy system via the incorporation of an aerobic reactor; system characterisation the main objective.
The laboratory apparatus was characterised over several experiments to establish optimal operating conditions for re-aeration, nitrification, and biomass production. Both equipment configuration (dissolved oxygen (DO) probe and air source (air stone) direction) and aeration parameter combinations (air saturation and retention times (THRT)) were examined either with or without a returned activated sludge (RAS) feedback step. Based on this research aeration was found to be most proficient when air was directed in towards the centre of the vessel with the DO probe placed just below the water’s surface (4-6 cm). Once optimally configured, nitrification and removal rates were 52-79% SS and 24-90% NH4+-N respectively. Low nitrification rates were exhibited during the earlier trials at each parameter set. However, the incorporation of a 20% RAS, significantly improved nitrification performances with greater nitrate accumulation detected.
Once suitable conditions were obtained, the algal growth potential was examined in the treated waste signifying a successful growth pattern after 21 days of continuous light exposure. Thus, highlighting the need for an integrated treatment step.
Success of this integrated treatment technology would not only revolutionise the pork industry’s outlook on pig effluent as an important potential sustainable source of renewable energy but also enhance profitability with on-site energy, heat, and cleaner wastewater production for subsequent beneficial reuse.
Keywords: Anaerobic pig slurry, aeration, integrated wastewater treatment systems, nitrification, dissolved oxygen, suspended solids, ammonia removal
Subject: Environmental Science thesis, Water Management thesis
Thesis type: Doctor of Philosophy
Completed: 2019
School: College of Science and Engineering
Supervisor: Prof. Howard Fallowfield