Submitted to: Transactions of the ASAE
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: May 26, 1999
Publication Date: N/A
Interpretive Summary: Organic nutrients and volatile solids in liquid swine manure are important to both agricultural crop production and environmental quality. They are mostly contained in fine suspended particles that are not separated by available mechanical separators. In this study, for example, only 5 to 14% of the volatile suspended solids (VSS) and 10 to 20% of organic nutrients were removed by a 1-mm screen. Treatment with polyacrylamide (PAM) polyme flocculants prior to mechanical removal has the potential for enhancing solids separation. Our evaluation showed that the PAMs with positive charges were most effective. Removal efficiencies for total suspended solids (TSS) and VSS were high (>90%); Optimum PAM rates were 26 and 79 mg/L for liquid manure containing 1.5 and 4.1 g TSS/L, respectively. The polymer usage rate was about 2.0% of the dry solids produced and estimated cost was $0.026/hog/day. Organic nutrients removal efficiences followed a relationship with TSS removal efficiency. Large solids removal can help i the control of odor from existing lagoons. The proposed technology provides an attractive alternative to existing liquid manute management methods. It, thus, expands options for environmentally sound and sustainable swine productions. .
Technical Abstract: Most of the organic nutrients and reduced carbon (C) materials in liquid swine manure are contained in fine suspended particles that are not separated by available mechanical separators. Treatment with polyacrylamide (PAM) polymers prior to mechanical removal or gravity settling has the potential for enhancing solids-liquid separation, thus concentrating nitrogen (N), phosphorous (P), and organic C. In this work, we determined PAM charge and density characteristics most desirable for swine wastewater applications and established optimum chemical requirement. Flushed manure samples were obtained from two farms in North Carolina. Cationic PAMs significantly increased solids separation, but performance of neutral and anionic types was not different from a control. Within the cationic PAMs, moderately charged materials (20%) were more effective than polymers with higher charge density. Optimum PAM rate varied with the amount of total suspended solids (TSS) in the liquid manure; 26 and 79 mg PAM/L for sample containing 1.5 and 4.1 g TSS/L, respectively. Corresponding TSS removal efficiencies were 90 to 94%. In contrast, screening without PAM treatment captured only 5 to 14% of TSS. Polymer usage rate averaged 2.0% based on weight of dry solids produced. Volatile suspended solids (VSS) were highly correlated with TSS and comprised 79.5% of TSS. Organic nutrient and COD concentrations in the effluent were also significantly decreased by PAM treatment. Removal efficiency of organic N and P followed approximately a 1:1 relationship with removal efficiency of TSS. Chemical cost to capture 90% of the suspended solids was estimated to be $0.026 per hog per day. Results obtained indicate that PAM treatment is very effective for removal of suspended solids, COD, and nutrients from flushed swine manure.