The study of constructed wetland for treating livestock wastewater and the livestock sludge compost
In Taiwan, swine wastewater has become one of the major causes of the deterioration of surface water quality. To minimize the operational and maintenance cost of the conventional wastewater treatment utilities, less expensive natural treatment systems (e.g., aquatic plant treatment system) have been proposed to enhance the efficacy of existing three-stage treatment system (solid separation followed by anaerobic and aerobic treatment). Using the natural treatment system is an appropriate technology for treating livestock wastewater in tropical or subtropical regions or developing countries because it is inexpensive, easily maintained, and has environmentally friendly and sustainable characteristics. The main objectives of this study were to (1) examine the efficacy and capacity of using aquatic plant treatment system to polish the treated wastewater to meet the discharge standards in Taiwan (COD = 600 mg/L, BOD = 80 mg/L, and SS = 150 mg/L), (2) evaluate the potential of reusing the treated wastewater, (3) evaluate the feasibility of replacing the aerobic treatment process contained in the three-stage system with the aquatic plant system, and (4) improve the efficiency of sludge (obtained from the three-stage treatment system) composting process. In this study, a hog farm was selected as the case study site. An aquatic plant unit [13.5 (L) ¡Ñ 4 (W) ¡Ñ 3 (D)] planted with Eichhornia crassipes (water hyacinth) was placed after the aerobic system for wastewater polishment. Influent and effluent sa mples from each unit were collected and analyzed for water quality parameters including chemical oxygen demand (COD), biochemical oxygen demand (BOD), and suspended solids (SS). Water samples were collected monthly during the 15-month investigation period. Results show that the averaged COD, BOD, and SS concentrations were approximately 708, 83, and 123 mg/L, respectively after the three-stage treatment scheme. The observed COD, BOD, and SS concentrations dropped to 518, 56, and 48 mg/L, respectively which could meet the discharge standards. Thus, the aquatic plant treatment system played an important role in meeting the discharge standards for swine wastewater. More than 99% of all pollutants were removed by the three-stage system followed by the aquatic plant system. The effluent from the treatment system has been used for hog farm cleaning. Thus, the aquatic plant system has the potential to be applied as the final polishment process to enhance the treatment efficacy of swine wastewater. Results also show that it is feasible to replace the aerobic treatment process with the aquatic plant system from the cost and regulation compliance point of view. Results from the composting study show that rice straws could enhance the activity of microorganisms and also cause the increase the quantity of potassium in the compost pile. Moreover, mixing the water hyacinth in the compost pile could increase the quantity of nitrogen and phosphorous. Results also reveal that using ceramic bioballs as the filling materials could minimize the composting time due to the increase of permeability in the piles.
Advisor:Lei Yang; Ching-shu Jen; Chia-i Tsai; Jimmy Kao
School:National Sun Yat-Sen University
School Location:China - Taiwan
Source Type:Master's Thesis
Keywords:sludge constructed wetlands water reuse hyacinth aquatic plant system livestock wastewater compost
Date of Publication:08/18/2005