Study On Greenhouse-structured Multilayer Constructed Wetland For Domestic Sewage Treatment In Frigid And Anoxic Climate

The Tibet autonomous region is the main representative of alpine hypoxia area, where the climate characteristics of hypoxia, perennial cold with large temperature difference day and night. In view of the special natural environment, the decont amination effect of conventional wastewater treatment technology is not good, and the construction cost is extremely high,beyond the capacity of the region of relatively backward economy and technology. The popularity of Constructed wetlands?CWs? for wastewater treatment is increasing worldwide,because it has high pollutant removal efficiency, low cost and simple operation. However, the application of CWs system is restricted in Tibet for the roof of the world and the frigid and anoxic climate can affect the removal of contaminants.This paper describes a project of domestic sewage treatment, which utilized novel greenhouse-structured multilayer constructed wetland?GMCW? in Tibetan Plateau. Through experimental study and demonstration project to determine the process of running effect,influence factors, and further optimize the design and operating parameters, and then to provide the reference basis for the region's sewage treatment engineering design, construction and operation management. Paper main research contents and results are as fol lows:?1?The experiment of isothermal adsorption and dynamic characteristics of packing column has completed for local dielectric materials such as perforated brick, limestone, gravel,iron slag and hot spring stone. The results show that perfor mance of perforated brick best, and further determining the structure of multilayer constructed wet land system, its main loading medium for perforated brick, limestone and gravel. After a small experimental device and continuous operation of demonstration project, perforated brick, limestone and so on substrate surface features compared with the early running, obvious changes have taken place. The microbes to achieve ideal condition, andclogging situation did not occur.?2? According to the characteristics of water quality and climate characteristics of Tibet,some ornamental plants from Lhasalalu wetland including Phragmites australis, Sparganium and Scirpus tabernaemontani, has planted in the MCW system. Experimental study on the growth characteristics of plant and the influence of different planting plan for sewage purification effect has completed. The results show that Sparganium and Scirpustabernaemontani is suitable for planting in greenhouse, Phragmites australis not suitable for planting due to growing weaker, and mixed wetland plant interplanting way a single plant growing in the sewage treatment effect. The decontamination effect of wetland plant mixed interplanting way significantly better than that of single planting. Analys is from the use of engineering technology, still need to find local wet land plant, its characteristics such as developed root, growth cycle longer, can crop rotation in winter under greenhouse,intercropped with existing plants to ensure the system run efficiently all the year round.?3? In the study of t he characteristics of the greenhouse, emphatically introduces the heat preservation effect of greenhouse, the results show that the greenhouse can be competent for the runing of artificial wetland treatment system, and has an obvious effect at stable operation of process system. However, the insulation ability of greenhouse in night is relatively poor in winter under the larger temperature difference. In order to achieve better heat preservation effect, suggest set up the thermal insulation material outside the greenhouse.?4? In medium test device of mul tilayer constructed wetland, explore the optimization of process design and operation parameters, by changing the length-width ratio of wetland bed,hydraulic load, water temperature, adding preprocessor facil ities and aeration mode. Results showed that the length-width ratio of wetland bed should be set up at about 3:1, hydraulic load control in 0.25 m³/m²·d, not need to add biological pretreatment, the need for heating equipment and aeration equipment.?5? Comparing study on the different structure of constructed wetland, loading plan, plant configuration and greenhouse thermal insulation properties in the 1000m³/d demonstration project. Results showed that the decontam ination effect is good about COD, NH₄⁺-N, TN and TP in greenhouse-structured multilayer constructed wetland unit, which is superior to I?A?level of discharge standard of pollutants for municipal wastewater treatment plant of China?GB 18918-2002?.