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Flocculation Of Swine Manure: Influence Of Flocculant, Rate Of Addition, And Diet

Published by the American Society of Agricultural and Biological Engineers, St. Joseph, Michigan

Citation:  Paper number  024157,  2002 ASAE Annual Meeting . (doi: 10.13031/2013.9336) @2002
Authors:   Wendy Powers, Laura Flatow
Keywords:   Phosphorus, Flocculation, Manure

Manure was collected from growing pigs (22 to 48 kg) fed one of 11 varying in total and available phosphorus content diets during each of three feeding periods. Reduced phosphorus diets were amended with feed additives intended to improve availability of phytate phosphorus. Dietary non-phytate phosphorus content was adjusted during each feeding period according to animal needs that changed as animals grew. Dietary strategies were replicated over three feeding periods resulting in 33 diets and corresponding manure samples. Collected manure samples were diluted (final solids content approximated 0.24% total solids), stirred in 1000 ml beakers, and poured into Imhoff cones. Five flocculants plus a control were added at each of three concentrations, and the diluted mixtures were allowed to settle for two 10-min settling periods. Volume of settled material was recorded following each settling period. At the end of the second settling period (20 min total settling) supernatant was subsampled and frozen for future phosphorus analysis, and settled solids were weighed and dried for total solids determination. Phosphorus and solids recovery was calculated. Results indicated that Al2(SO4)3 and FeCl3 were the most effective flocculants. Little improvement was observed when the flocculant was added at a concentration of 625 mg flocculant/L compared to 250 mg flocculant/L. Both flocculants recovered over 85% of solids and over 70% of the phosphorus. Addition of Al2(SO4)3 at a concentration of 625 mg/L increased phosphorus removal to 90%. Diet, feeding period, and the interaction of diet and feeding period were significant influences on solids settling, solids settled after 10 min setling time compared to 20 min, and phosphorus settling. Inclusion of dietary additives did not clearly influence results. As the pigs aged, manure phosphorus was more soluble, possibly explaining the observation that less phosphorus was settled in feeding period 3 compared to periods 1 and 2. As producers consider nutrient management options feed-tofield strategies, that look at nutrient reduction strategies at multiple steps in a whole-farm plan, should be implemented. Prediction equations were developed to estimate solids and phosphorus removals for each flocculant tested.

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