Construction Of Integrated Constructed Wetland System And Its Purification Effect On Water Quality

Constructed wetland is an ideal way to deal with aquaculture drainage,due to the low capital cost,high efficiency characteristics,and the economic,social and ecological values.The use of constructed wetland decontamination technology has become a hotspot,in recent decades.Constructed wetland is a simulation of the structure and function of natural wetlands.The purification of water pollutants achieved by the interactions between the plant,matrix and microbial,and the physical,chemical and biological processes.Constructed wetlands have been widely used to treat domestic aquaculture drainage,industrial wastewater,aquaculture drainage and agricultural point source pollution and non-point source pollution and other eutrophic water management.However,there are many deficiencies in constructed wetlands.For example: large space occupation,cannot be long-term stability during the operation,the lower removal efficiency of nitrogen and phosphorus,prone to clogging,and the non-uniform or non-standard of design parameters.In order to solve the problems existing in the operation of constructed wetland,constructed wetland and constructed wetland-biological filter decontamination systems were constructed,and the effect of purification on the aquaculture drainage was studied.It is hoped that it can be fully utilized to achieve the effective decontamination effect of the aquaculture drainage,and provide some reference value and technical support for the construction of the aquaculture drainage decontamination theory.The main conclusions are as follows:（1）In order to study the discontinuous water purification of seawater aquaculture drainage,integrated vertical-flow constructed wetland（IVCW）was constructed with acrylic.The length,width and height were 100.00 cm × 60.00 cm × 100.00 cm.It was composed of downstream pool,upstream pool,sedimentation tank and so on.The results showed that IVCW had good effect on the removal of potassium permanganate（CODMn）,ammonia nitrogen（NH4+-N）,total nitrogen（TN）and total phosphorus（TP）in the aquaculture drainage.The basic parameters of the drainage during the experiment were as follows,temperature was（26.62±0.64）℃,dissolved oxygen（DO）was（5.79±0.28）mg/L,pH was 7.67±0.05.The concentrations of CODMn,phosphate and TP were（3.7±0.8）mg/L,（0.03±0.01）mg/L and（0.06±0.01）mg/L,respectively.The average removal efficiency of CODMn,phosphate and TP were（70.54±7.8）%,（93.34±1.07）% and（91.56±0.91）%,respectively.The average removal efficiency of NH4+-N was（78.52±4.37）% and the highest was 85.36%.The concentration of TN was stable at 1.07 mg/L and the average removal efficiency was（47.24±4.33）%.The concentration of CODMn meet the First Grade Standard of（SC/T 9103-2007）.The concentrations of pH and NH4+-N meet the（GB 11607-89）and the First Grade Standard of（SC/T 9103-2007）.（2）In order to explore the purification effect of constructed wetland-biological filter decontamination process on pollutants in circulating aquaculture,a composite constructed wetland system was constructed.The system was composed of aquaculture pond,biological filter,storage tank,constructed wetland and sedimentation tank.Both constructed wetlands and biological filter are segmented.The system has an area and volume of 1.30 m2 and 910.00 L,respectively.Constructed wetlands and biological filter were coral,gravel and biochemical filter,explosive cotton,respectively.The results showed that the composite wetland system had good effect on the purification of CODMn,phosphate,TP,NH4+-N and TN.The daily effluent concentration was stable,and the system had strong anti-pollution load capacity.The concentrations of CODMn,phosphate and TP were（3.2±0.8）mg/L,（0.08±0.01）mg/L and（0.10±0.01）mg/L,respectively,in fresh water system.The concentrations of CODMn,phosphate and TP were（5.3±0.7）mg/L,（0.05±0.01）mg/L and（0.07±0.01）mg/L,respectively.The average concentration of NH4+-N was（0.04±0.02）mg/L in both system,and the average concentration of freshwater and seawater system were（4.51±0.77）mg/L and（4.62±0.63）mg/L,respectively.The pH and concentrations of CODMn,P,TP and TN meet the（SC/T 9101-2007）and（SC/T 9103-2007）.The concentration of NH4+-N meet the（GB 11607-89）.In the composite constructed wetland system,there are deficiencies of space utilization,and the effective area and volume were low,accounting for 43.85% and 36.92%,respectively.Due to the system pipes were too long,the contaminants accumulated in the wall,the flow rate became slow,water quality was instability.（3）In order to solve the problems existing in the operation of the composite constructed wetland system,an integrated constructed wetland system was designed and constructed.Decontamination units are miniaturized,directly connected,no need for piping,and effective area and volume ratios close to 100%.The types and methods of fillers for constructed wetlands and biological filter are the same as those of composite constructed wetland systems,and distributed designs are used internally.The results show that the two systems had poor ability to purify pollutants during the experiment,and the concentration of each pollutant fluctuated greatly.The concentrations of CODMn,phosphate and TP were（6.2±1.2）mg/L,（0.06±0.02）mg/L and（0.08±0.02）mg/L,respectively,in the system 1.The concentrations of CODMn,phosphate and TP were（4.6±0.8）mg/L,（0.03±0.02）mg/L and（0.05±0.02）mg/L,respectively,in the system 2.The average concentrations of NH4+-N and TN were（2.36±1.04）mg/L and（7.34±2.50）mg/L,respectively,in the system 1.That were（2.65±0.96）mg/L and（7.29±1.79）mg/L,respectively,in the system 2.The pH and concentrations of P and CODMn meet the（SC/T 9103-2007）,but the NH₄⁺-N.