Construction Of New Type Siphon Oxygenated Constructed Wetland And Its Optimal Operation

As a technology for wastewater advanced treatment using bio-ecological methods,constructed wetland technology has high buffering capacity for hydraulic and pollution loads,can effectively and reliably treat wastewater for a long period of time,has low construction and operation costs,and is easy to maintain and manage.In the past ten years or so.cities and provinces including Shandong Province have been widely used in the treatment of various types of sewage such as polluted river water,urban sewage plant effluent,and rural dispersed domestic sewage.In order to solve the problem of oxygen supplementation in the existing constructed wetland,this paper proposes a new type of siphon-oxygenated constructed wetland system based on oxygen regulation,namely:(1)On the basis of the traditional vertical subsurface flow constructed wetland.the wetland drainage port is changed into an inverted U-shaped siphon drainage pipe.so that the wetland forms a periodic siphon drainage during the continuous water inflow and liquid level change,so that the substrates upper channel of the drainage can periodically exposed to the atmosphere,and the wetland system is capable of efficient oxygen and water purification.The system runs automatically throughout the entire process without the need for external forces.(2)By setting a baffle inside the wetland to optimize the water flow path,the influent water flows through the aerobic functional zone periodically exposed to the gas phase in the central upper portion,the anaerobic functional zone in the long-term submerged state at the bottom.and the periodic upper peripheral exposure.So that the alternating aerobic-anaerobic environment can be formed in the svstem.Based on the above ideas,this paper mainly studies the following three aspects:the basic operating characteristics of the new wetland system and the effect of oxygen supplementation.By comparing with traditional wetland and aeration enhanced wetland,the basic removal effect of COD,TN and other pollutants and the effect of oxygen supplementation in the new siphon wetland were explored.The study was carried out to control the oxygen distribution in the new wetland system by changing the height of the siphon outlet pipe(That is to change the proportion of aerobic-anaerobic zone inside the system)and investigate the effect of the proportional change on the water purification of the system;further optimize the system design,further improve the influent C/N ratio and add fiber slivers in the unsaturated zone at the inlet end.Improve the effect of wetland systems on wastewater treatment.The main conclusions obtained are as follows:(1)Exploring the effect of oxygen supplementation on the new type of siphon wetland:First,directly observe the dissolved oxygen in the traditional group,the aeration group,and the new siphon wetland:the instantaneous dissolved oxygen peak that can be reached in the siphon wetland system at all monitoring points.At 4.58 mg/L,the dissolved oxygen stabilized at 0-0.5 mg/L when the substrate was flooded for a long time.The aeration group was stable at 5-7 mg/L and the traditional group 0-0.5 mg/L.The second was to analyze the related gene abundance by performing Q-PCR gene analysis on three groups of systems:The absolute abundance value of amoA gene in the siphon wetland group was up to 2.83 × 107 copies/g.which was similar to the highest gene abundance of 2.99 ×107 copies/g in all monitoring points in the aeration group.It is proved from the above two aspects that the new siphon wetland has a certain oxygen supplement effect under the condition of no external power.In addition,the results of MLSS measurement showed that the MLSS content of each monitoring point in the siphon experimental group was lower than that of the traditional wetland and aerated wetland.The reason may be related to the shedding of the biofilm on the surface of the substrate when the water is rapidly drained,which is beneficial for the anti-blocking of the wetland.(2)In a certain size of the siphon wetland system,along with the increase of the height of the water outlet,the proportion of the long-term flooding area in the system also increases.In the four groups of control experimental groups,the proportion of long-term inundation area was 4.17%,34.72%,50%,and 80.56%,respectively,but at the same time,the aerobic environment area gradually shrank,and the removal rate of ammonia nitrogen decreased from 51.05%to 39.24%.However,TN The removal rate increased from 16.21%to 27.71%.The water quality change data along the course showed that about 90%of the influent COD was consumed in the 1/8 interval before the whole flow,and then the COD concentration in the system fluctuated between 10 and 30 mg/L.(3)On the basis of maintaining a sufficient volume of anaerobic area inside the irrigated wetland system,the burial of a certain length of cotton strip in the unsaturated section of the inlet end contributes to the improvement of the overall aerobic conditions in the system.The removal rates of ammonia nitrogen in control group 1 and experimental group were 45.57%and 51.87%,respectively,and the removal rate of ammonia nitrogen in control group without cotton strip was 25.06%.The improvement of the available carbon source in the wetland is of great significance for the removal of TN and TP:in the removal of TN,the removal rates of control group Ⅰ,Ⅱ and experimental group were 22.30%.30.78%.39.10%.respectively;The removal rates of TP were 19.13%,31.7%,and 42.36%,respectively.