Phosphorus, copper and zinc in solid and liquid fractions from full-scale and laboratory-separated pig slurry.

Pig slurry separation is a slurry treatment technique that can reduce excess loads of P, Cu and Zn to the arable land. This study investigated the effects of different commercial and laboratory separation treatments for pig slurry on P, Cu and Zn distribution into solid and liquid fractions. Solid and liquid separation fractions were collected from two commercial separators installed on the farm. Five different separation treatments were performed (polymer flocculation and drainage; coagulation with iron sulphate addition and polymer flocculation and drainage; ozonation and centrifugation; centrifugation only; and natural sedimentation) on sow and suckling piglet raw slurry. Particle size fractionation was performed on raw slurry and all separation fractions by sequential wet sieving and P, Cu and Zn concentrations were then measured in the particle size classes. Dry matter and total P, Cu and Zn were separated with higher efficiency when chemical pretreatments with flocculants and coagulants were introduced before mechanical separation at both commercial and laboratory scale. When solid fractions are utilized as crop fertilizer (primarily as P fertilizer), the loads of Cu and Zn to the soils are not markedly different than the loads applied with raw slurry. When liquid fractions are used as crop fertilizer (primarily as N fertilizer), the loads of Cu and Zn are markedly lower than those supplied with raw slurry. The loads of Cu and Zn introduced to the soil were lowest on application of the liquid fraction produced by optimized separation treatments that included flocculation and coagulation.

Carbon, nitrogen, and phosphorus distribution in particle size-fractionated separated pig and cattle slurry.

Solid liquid separation of animal slurry is a method to reduce the excess nutrient loads from intensive livestock production. Five different separation technologies (sedimentation, centrifugation, pressurized filtration, polymer flocculation and drainage, and iron chloride addition + polymer flocculation and drainage) were applied to pig and cattle slurry in a laboratory study. Separation efficiencies of mass, dry matter (DM), N, and P were measured. Particle size fractionation of the solid fractions was performed by subjecting them to wet fractionation and C, organic N (N(org)), and P contents were subsequently measured. Chemical pretreatment with polymer before gravity drainage separated DM, total N, and P from raw pig and cattle slurry with the highest efficiencies. Sedimentation and centrifugation separated P from pig and cattle slurries with higher simple separation efficiencies (0.77 and 0.70, respectively) compared with pressurized filtration (0.15 and 0.37). Pressurized filtration transferred the lowest masses (14 and 18%) to the solid fractions. Solid fractions from pig slurry generally contained higher concentrations of P and C compared with cattle slurry solid fractions. The majority of C in solid fractions was present in particles > 25 microm, whereas N and P were present in larger proportions in particles < 25 microm. Chemical pretreatment increased the capture of smaller N(org)- and P-rich particles into larger particles between 25 and 1000 microm.

Flocculation, coagulation, and precipitation of manure affecting three separation techniques.

The effects of polymer flocculation before manure separation were investigated, through testing both a linear and a branched polymer. Centrifugation removed 60% of phosphorus from raw manure (control), whereas raw manure clogged the filters during gravity drainage and pressure filtration. At optimum flocculation, 95% of phosphorus was removed using any of the three methods. Optimum flocculation was achieved when 2.8meq of polymer charge was added per kg of manure, corresponding to 0.6g/kg of highly charged, branched polymer or 0.85g/kg of less-charged, linear polymer. If 10mmol of ferric chloride was added per kg of manure, 2% more phosphorus was precipitated and removed. The linear polymer formed loose flocs and was superior for reducing turbidity, whereas the branched polymer formed compact flocs that deflocculated at high polymer doses. The branched polymer, however, was best for pressure filtration, as overdosing with the linear polymer resulted in high resistance.