Treating domestic wastewater with aerated taro constructed wasteland

Domestic wastewater discharged from residences, commercial facilities, and institutions can be a valuable resource in fast growing cities or towns where water supplies are becoming limited. Treated or reclaimed wastewater may be used for crop and landscape irrigation, groundwater recharge, or recreational purposes, depending on the level of treatment. However, wastewater treatment is usually expensive. The authors studied the potential of mimicking natural processes in wetland ecosystems as a cheap, low-cost, and environment-friendly option for treating domestic wastewater. The study tested the effectiveness of introducing aeration and planting of taro in constructed wetland technology (which is already being utilized in the US to treat wastewater and stormwater) to remove pollutants and contaminants associated with domestic wastewater such as suspended solids, N, P, hydrocarbons, and metals. To simulate constructed wetland conditions, a 1.10 m x 2.20 m x 0.60 m marine plywood box sealed with epoxy was fabricated. Raw domestic wastewater from the researcher's residence septic tank was introduced maintaining a volume of 678 L. Twenty-four taro plants were introduced into the cell together with an aerator with an output of 14 L/minute. Samples of the effluent were taken 7 and 14 days after introduction of the wastewater into the cell and then analyzed for Biochemical Oxygen Demand (BOD), Dissolved Oxygen (DO), Total Kjeldahl Nitrogen (TKN), Total Suspended Solids (TSS), and pH. The results were evaluated for significance using T-test, and compared with the standards set by DENR Department Administrative Order (DAO) No. 35, Series of 1990. The experiment was conducted in Sanroe Subdivision, San Roque, Gov. Ramos Avenue, Zamboanga City [Philippines]. Aerated, constructed wetland employing taro can be used in the treatment of domestic wastewater particularly sillage or grey water. The longer the detention time in the constructed wetland, the higher the removal of BOD. Mean removal at seven days was only 17.76% at 14 days detention period than at seven days (33.3%). TKN removal rate was 69.13% at seven days detention time, and 57.87% at 14 days, although not significantly different. Mean pH of effluents was almost neutral. DO increased from 0-2.58 mg/L and 2.303 mg/L in 7 and 14 days detention period, respectively. All mean BOD 5 effluent results at 7 and 14 days did not satisfy the standards stipulated under DENR DAO No. 35, S. 1990 for disposal to class C inland water. However, the disposal requirement to class SC coastal water was satisfied. Researchers recommended that further investigation be conducted using greater depth, different wastewater and aquatic plants, longer detention time, and harvesting