| In recent years, the application of constructed wetlands in pond aquaculture is more and more extensive. A water treatment system suitable for rice cultivation was designed and constructed. The comprehensive application effect of the integrated constructed wetland in pond aquaculture was studied in order to provide more scientific basis for the application of constructed wetland in pond culture and water pollution control. The main results are as follows:(1)An integrated constructed wetland which is suitable for economic plant cultivation and water quality improvement is designed and constructed. The system is an impervious brick masonry and the size is about 25 m x 17 m x 1m, which is composed of water inletpart, planting part and water collection part. The water inlet part includes a water distribution tank and a gravel layer composed of a 90 cm and the particle size of 8~15cm. Waste water flows through the water distribution system, and the pebble layer plays the role of re-filtering. The planting area is filled with 30~40cm thick gravel, and the floating plate is used to carry out water on the floating plate.The size of the floating plate is about 0.5 m x 0.5 m x 0.08 m, and each floating plate has 4 planting holes, planting density for 9.24 ind./m~2, floating Plate coverage rate of57.8%. The water collection part is composed of a water collecting pipe and a drainage ditch which are arranged at the bottom of the medium layer.(2)The optimum operating parameters of the integrated constructed wetland were studied. In the experiment, the continuous feed- retention reaction, continuous water discharge, and the discharge of the idle mode were used. The effects of different aeration intensity on the water treatment capacity of the combined wetland were discussed respectively. The experimental optimization results show that the system can get better water treatment effect when the hydraulic load is 0.29m/d~0.58m/d and the gas water ratio is 2~4. The study of combined the water treatment system withpond culture shows that the removal rates of TAN, TN, TP and CODMn were32.66%~35.57%, 59.17%~64.36%, 69.45%~74.54% and 70.24%~ 75.43% when the hydraulic loading is 0.58m/d and the gas water ratio is 2. All parameters except dissolved oxygen of outlet from the water treatment system could meet the standard of national fishery water quality(GB11607).(3) Discussion on integrated constructed wetland pond water purification effect.June – October 2015, six intensive pond area of 400m~2 had been selected, four of this combined with integrated constructed wetland formed an Integrated Constructed Wetland-aquaculture Pond Ecosystem, two as a control pond, study on the effect of integrated constructed wetland to fine aquarium water quality. The results show, by integrated constructed wetland processing, integrated pond water has been effectively controlled, the various water physic-chemical parameter are mean value for: SD 18.42 cm, p H is 7.96, DO 4.49 mg/L, CODMn 19.87 mg/L, TAN 1.03 mg?L-1, NO2--N 0.05mg/L, TN 5.37 mg/L and TP 1.16 mg?L-1.(4) Study on the effect of different pond culture system and the nitrogen and phosphorus budget. The main results are as follows: The harvest specifications,survival rate and yieldof major cultured fishes in circulation pond are 0.38 kg, 71.41%and 10054.38 kg/hm~2, which is significantly higher than control pond. Rice yield was7127.01 kg/hm~2, compared with that in the same period, the yield decreased by23.02%. The utilization ratio of nitrogen and phosphorus in circulation pond was48.11% and 25.10%, respectively, and control pond was only 32.05% and 18.57%.The sedimentation of nitrogen and phosphorus plays a major role in nitrogen and phosphorus removal, and its contribution is 21.08% and 42.04% respectively in circulation pond, which is less than control pond. The nitrogen and phosphorus emission intensity was 4.91 kg/400m~2 and 0.99 kg/400m~2, while the composite pond water body could be reused. The integrated culture system which is formed by the connection of the integrated constructed wetland can effectively control the nitrogen and phosphorus output of the main project, and it increased the utilization ratio of nitrogen and phosphorus and the yield. The integrated culture system can effectively reduce nitrogen and phosphorus in sediment, reducing the possibility of the outbreak of endogenous pollution in aquaculture ponds, and enhance the survival rate of fish,which is conducive to the healthy development of aquaculture ponds.(5) The comprehensive benefit of the integrated wetland pond culture model wasdiscussed. The main results are as follows: Operating of circulating pond costs more,but it has a higher margin. Circular pond net income was 26300 yuan /hm~2, while the control pond was only 14900 yuan /hm~2. The comprehensive effect index was 1.05 of Circular pond and 0.84 of control pond. The results show that the recirculating aquaculture system can significantly improve the output and economic benefits, both economic and ecological benefits and advantages. |
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