Nutrient Removal from Anaerobically Treated Swine Wastewater by Duckweed in Lab-Scale Stabilization Ponds in Vietnam

摘要

This research aims to demonstrate the applicability of an aquatic plant duckweed (Lemna Minor) to water purification in the household swine wastewater treatment system. The 10-fold diluted wastewater after anaerobic treatment was continuously fed to lab-scale stabilization ponds planted with/without duckweed at a hydraulic retention time of 5 days under ambient condition in Hanoi, Vietnam. The chemical oxygen demand (COD), total nitrogen (T-N), and total phosphorus (T-P) concentrations in the diluted wastewater were 260-290 mg/L, 24-28 mg/L, and 1.4-1.8 mg/L, respectively. The duckweed drastically enhanced the first-order removal rates by 1.4, 2.0, and 3.2 times for COD, T-N, and T-P, respectively. The COD, T-N, T-P removals in the pond with duckweed (74%, 84%, 84%) were much higher than the pond without duckweed (71%, 55%, 58%). The duckweed grown with the relative growth rate of 0.07-0.16 d~(-1) should uptake nutrients from the wastewater. Biofilm formed on the duckweed roots possibly promoted biodegradation of organic matter. The harvested biomass of the duckweed can be used for animal feed. The stabilization pond planted with duckweed will be a co-beneficial system for wastewater treatment and biomass production.