Study on method of domestic wastewater treatment through new-type multi-layer artificial wetland

The artificial wetland is comprised of such groundmasses as breakstone and gravel etc as well as aquatic plant attached to it. The wastewater flows in or beneath surface layer of groundmass at the wetland, and decomposes nutritive materials in water through such a serial processes as attachment to groundmass, absorption by plant and microbial conversion etc, which belongs to distinctive soil-plant-microbe system that is differentiated from the wetland. This paper introduces a new-type multi-layer artificial wetland for treatment of domestic sewage, and analyzes the removing effects of CODCr, BOD5, NH3-N, TN and TP in this approach. The results indicate that when hydraulic loading reaches approximately 0.44 m3/(m2 d) and hydraulic retaining duration reaches 3 days, the effect of removing CODCr, BOD5, NH3-N, TN and TP from the wetland is relatively good, and the average removing rate achieves 90.6%, 87.9%, 66.7%, 63.4 and 92.6% respectively, and the effluent CODCr reaches approximately 14.1∼30.8 mg/L, BOD5 reaches approximately 8.2∼13.1 mg/L,NH3-N reaches approximately 9.9∼19.6 mg/L, TN reaches approximately 17.3∼28.7 mg/L and TP reaches less than 1.2 mg/L. Thus the effluent exceeds farmland irrigation water quality standards (GB5084-2005). Such factors as planting density, temperature variation and influent contaminant concentration have relatively great correlation with efficiency of wetland treatment. Generally speaking, when the temperature is higher than 24 °C, the higher planting density and lower contaminant concentration reaches, the better effect of the treatment would realize.