WA0206-WA0209. Livestock wastes: reduction of pollution and odour
This study (which comprises projects WA0206, WA0207, WA0208 and WA0209) will aim to investigate economically viable methods for the treatment, storage and handling of farm wastes to avoid pollution of water courses, creation of a nuisance due to odour and loss of valuable organic C and nutrients. Firstly, efficient process strategies will be devised for aeration of slurry, in order to control odours, reduce water pollution, kill pathogens and conserve N. A mathematical model will be developed to describe the performance of slurry aeration plants, based on previously gathered experimental data and information from the literature. Experiments will also be conducted, using pilot scale aeration plants, to gather detailed information on process parameters including volatile fatty acid concentrations, biochemical O2 demand, odour strength, energy requirements, pathogen kills and N losses. Results predicted by the model and pilot scale experiments will be tested on a farm scale and a comprehensive, systematic guide for slurry aeration plants will be produced. The basic physical and biochemical mechanisms of aeration will be investigated in order to construct designs for more efficient slurry aerators. A distributed parameter model will be created, relating O2 transfer to hydrodynamic conditions, together with pressure, temp. and slurry properties; the model will be verified using an existing tubular loop aerator facility. Large scale experiments will also be conducted to assess the performance of the pump-stirred aerator principle and an analytically based procedure for standardised evaluation of different types of slurry aerator will be created. Designs for least-cost biofilters will be devised as a relatively short term method for reduction of odour nuisance from livestock buildings. Laboratory scale experiments will be mounted to examine the effects of addition of biofilters on the ventilation systems of livestock buildings, biological performance of biofilter materials will be assessed on a pilot scale and the implications of these studies on design of full scale units will be evaluated. Finally, the basic processes involved in odour formation and release will be examined as a pre-requisite for identification of practical cost effective designs and management procedures for prevention of odours at source. Mathematical models will be constructed and controlled experiments will be conducted in specially designed chambers to quantify the influence of stock, environment, management and design factors on odour production in piggeries. The strategies proposed will then be evaluated under realistic farm conditions. It is anticipated that this work will lead to improved understanding of the many variables affecting aeration of slurry, reduction in biochemical O2 demand and the causes and persistence of odour.