Geotextile Filtration Performance for Lagoon Sludges and Liquid Animal Manures Dewatering
Maintenance and control of liquid levels in anaerobic lagoons and storage ponds is enhanced by pretreatment with liquid-solid separation or periodic removal of accumulated sludges. Until local disposal or nutrient recycling options become available, sludges can be contained, dewatered, and stored using geotextile filtration. A geotextile filtration testing method termed a hanging-bag test was used to treat dairy lagoon sludge, swine lagoon sludge, liquid dairy manure, and liquid swine manure. Hanging-bag performance was evaluated by: (1) determining solids and plant nutrient mass retention efficiencies (MRE), (2) quantifying the overall volume reduction, and (3) characterizing the dewatered manure. After three fill-dewater cycles, geotextile filtration performed similarly for the sludges, retaining an average 87.6% of total solids (TS), 58.4% of total ammoniacal nitrogen (TAN), and 86.7% total phosphorous (TP). Geotextile filtration was also effective in dewatering and concentrating the sludges; by highly concentrating the retained solids, it reduced the total influent sludge volume requiring disposal to less than 18.5%. Despite relatively high MRE values for liquid swine manure (70.2% of TS, 65.1% of TAN, and 75.7% of TP), geotextile filtration was ineffective as a primary liquid-solid separation, with 60.3% of the total influent volume remaining. For liquid dairy manure (TS = 0.71%), geotextile filtration reduced the total influent volume to less than 1%, concentrated the solids and nutrients in the dewatered material 16 to 21 times greater than the influent, and retained 38.4% of TS, 25.8% of TAN, and 45.0% of TP, making this an effective liquid-solid separation technique.