Purpose
To investigate the effects on pathogen reduction using cationic polymer and high speed centrifuge during manure solid/liquid separation.
What did we do?
In this study, polymers effects on pathogen reduction were investigated. Low charge density cationic polyacrylamide (CPAM) was selected because CPAM has been commonly used in manure treatment and it is effective for manure coagulation and flocculation. The effect on pathogen reduction of CPAM was studied in this research. High charge density cationic polydicyandiamide (PDCD) was selected because of its application of water clarification and its the extreme high charge.
E. coli and total coliform counts were examined under three different conditions: buffer media only samples, dairy manure samples and polymer amended dairy manure samples. For each condition, the samples were centrifuged at a series of speed from 0×g to 10,000×g.
What have we learned?
The results demonstrated positive impacts of both polymer and high speed centrifugation on lowering the pathogen levels in the liquid portion of the manure. Low charge density CPAM is effective for manure coagulation and flocculation, however, it has a negligible effect on pathogen reduction in either nutrient rich or nutrient deficient conditions. In contrast, highly charged cationic PDCD does not facilitate coagulation in manure with high solids content, but can potentially inhibit bacterial pathogens and further lower the solids content in the liquid portion of manure after CPAM separation.
The results from this study also demonstrated that high speed centrifugation has a notable impact on solids reduction and pathogen reduction for 10 minutes centrifugation retention time. Centrifugation speed around 4,000×g was capable of reducing pathogen levels higher than 90% from a single separation process. However, high speeds above 6,000×g results in minor additional reduction.
Future Plans
This study investigated cationic polymer and centrifuge speed impact on pathogen reduction and solid/liquid separation in dairy manure. However, there is an increasing concern about reactivation issue in centrifugation of mesophilically digested biosolids. Therefore we have attempted to conducted more research in the future regarding parallels to manure digestion. Until recently, it is still not fully understood why some municipal wastewater facilities experienced reactivation of microorganisms in centrifuged solids while others did not. Thus, it is important to investigate the effect of centrifuge speed in combination with polymer type on indicator and pathogen content of manure digests.
Authors
Troy Runge, Professor, Biological Systems Engineering, University of Wisconsin-Madison trunge@wisc.edu
Additional information
Journal papers have been submitted to Journal of Environmental Quality
Troy Runge, trunge@wisc.edu
Zong Liu, zliu73@wisc.edu
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