Use of geotextile tubes with chemical amendments to dewater dairy lagoon solids

Three geo-textile filtration tubes were used to dewater lagoon solids from a first stage dairy lagoon using chemical amendments (aluminum sulfate and a polymer) to enhance the separation process. This experiment had previously been done without chemical amendment. The chemical amendments speeded the dewatering process so that filling could be accomplished sooner, and also increased the removal rate of nutrients, especially phosphorus into the solid phase. Chemically amended slurry was pumped from the lagoon into the tube with the filtered liquid seeping from the tube and returning to the lagoon. Each tube was filled five to six times at 2-5-day intervals, and then allowed to dewater for 2 weeks before sampling the solid fraction in the tube. Separation efficiency improved from 79% to 99% for phosphorous and from 92% to 100% for organic nitrogen with chemical amendment. Time required for dewatering was significantly reduced by chemical amendment. Cost for the tube was approximately $10/m3 of recovered solids with no chemical amendment and cost including the chemicals was approximately $14/m3 of recovered solids.