| The Heosemys grandis is one of the main species of turtle breeding in Guangxi,and its breeding scale plays a certain role in the turtle breeding market in Guangxi.In order to understand the environmental quality of breeding water and the growth status of Heosemys grandis in different farming modes,this study selected circulating water from the turtle breeding center of the Animal Science and Technology College of Guangxi University from August 2017 to November 2017.The non-recycling water was used to monitor the culture of aquiculture ponds,sewage treatment ponds,and the growth status of Heosemys grandis.The circulation aquaculture model used the aquaculture wastewater recycling treatment pool system,and the recycling treatment system collected sewage.After multi-stage treatment,it is finally recycled through the aquatic plant purification tank;non-recycling aquaculture mode is to replace the water body by regular discharge.Each half a month was sampled at the turtle breeding center and tested for water quality,pH,dissolved oxygen,ammonia nitrogen,nitrite nitrogen,total nitrogen,total phosphorus,active phosphorus,COD,copper and zinc,etc.Indicators,and the use of surface water environmental quality standards,comprehensive water quality index method,water eutrophication footprint method to evaluate aquaculture water;at the beginning and end of the experiment were measured Heosemys grandis growth indicators;obtained The main pollution factors,water quality changes,and the effects of the circulatory system,etc.Different culture models Heosemys grandis breeding water quality changes and growth efficiency.At the same time,in order to collect and understand Guangxi’s breeding model of Heosemys grandis,this study also conducted field surveys on the Heosemys grandis breeding model and culture water quality at Beihai Hongzhao Agriculture Co.,Ltd.and Fangchenggang Fucheng Recreational Fishery Base.The main results are as follows:1.Under the circulating water model,the pH,dissolved oxygen,and copper content increased as a whole during the experiment.COD and total nitrogen showed a downward trend overall,and the regularity of ammonia nitrogen fluctuates up and down,and the active phosphorus is generally stable.Nitrite,total phosphorus,There was no obvious change in zinc content.Under the non-recycled water model,the overall pH showed an upward trend.COD,total nitrogen,and total phosphorus showed a downward trend.The dissolved oxygen,ammonia nitrogen,and copper content fluctuate regularly,and the active phosphorus was stable.There was no obvious change in the content of nitric acid and zinc.The COD and dissolved oxygen in the two models were significantly different(P=0.035,P=0.049).Circulating water has low dissolved oxygen and high COD.Statistical test analysis showed that there were significant differences in dissolved oxygen and COD in the dynamic changes of water quality under the pattern of circulating water and non-recycled water(P=0.035,P=0.049),and there was no significant difference among other factors(P>0.05).2.According to surface water environment quality standards for water quality evaluation,the total nitrogen and total phosphorus content in circulating water are 3.662mg/L and 0.916mg/L respectively,and 3.236mg/L and 0.595mg/L in non-recycling water,respectively.Surface water Ⅲ water quality standards were 2.66 times,3.58 times,2.39 times,and 1.58 times.Total nitrogen and total phosphorus in the circulating water were higher than non-recycled water.The average ratio of nitrogen to phosphorus of the rearing water and non-circulating water aquaculture models was 63.26.,72.34,all greater than 7,aquaculture water is limited by phosphorus nutrients.The remaining indicators other than total nitrogen and total phosphorus all meet the surface water environmental quality standards for fishery water use(Class Ⅲ).It shows that the main pollution factors of circulating water and non-recycling water in Heoseimys grandis aquaculture water are total nitrogen and total phosphorus.The characteristics of nitrogen imbalance are obvious and the imbalance of nitrogen and phosphorus in non-recycled water is more serious.3.Based on the eutrophication footprint analysis of ammonia,total nitrogen,and total phosphorus,the eutrophication footprints of total phosphorus and total nitrogen in circulating water and water were obtained from recycled water and non-recycling water.It is 2.47 times that of non-circulating water and 1.04 times.The eutrophication footprint of circulating water is 97.62×10-8kg NO3-eq,and the non-cyclical water eutrophication footprint is 55.04×10-8Kg NO3-eq.The circulating water is 1.77 times that of non-circulating water.Water is heavily polluted by nitrogen and phosphorus and total phosphorus contributes the most to eutrophication.According to the comprehensive water quality index index evaluation based on pH,dissolved oxygen,ammonia nitrogen,nitrite nitrogen,total nitrogen,total phosphorus,active phosphorus,COD,copper,and zinc,it was found that both the aquaculture water and the purified water of the recycled water system were Category Ⅲ water and non-circulating water systems have Class Ⅱ water,which are in line with aquaculture and other fishery water standards.4.During the study period,the water quality COD content in the circulatory system decreased from 16.00mg/L to 13.99mg/L,the total nitrogen content decreased from 3.662mg/L to 3.020mg/L,and the circulatory system removed COD and total nitrogen in the water.The removal rates were 12.5%and 17.5%,respectively,but the ammonia nitrogen and total phosphorus contents increased from 0.445mg/L to 0.464mg/L,respectively,and from 0.916mg/L to 1.702mg/L,an increase of 4.3%and 85.8%,respectively.The circulatory system has a certain removal effect on the COD and total nitrogen in aquaculture wastewater,but the water quality treatment effect is not ideal,and the water treatment efficiency needs to be improved.5.Analysis of growth and economic efficiency of Asiatic giant turtles during the study period:Under the mode of circulating water and non-recycling water,the average weight gain of Asiatic giant turtles was 210g and 183g,respectively.The profits of Asiatic giant turtles were 24,000 yuan and 9,000 million yuan,respectively.The growth and economic benefits of Asiatic giant turtle’s circulating water model were 1.15 and 2.67 times that of the non-cyclic model,respectively.6.A survey of the Heosemys grandis breeding mode and breeding water quality in the Beihai and Fangcheng two companies found that:There are three Heosemys grandis breeding modes in the two companies,namely,greenhouse cultivation,greenhouse-outdoor two-stage cultivation,and original ecological breeding.The water quality evaluation results of comprehensive water quality index method show that the greenhouse water is polluted by nitrogen and phosphorus,and the water body is typeⅣ water;the two-stage aquaculture water body is better,and it is judged as type Ⅱ water;the water quality in the original ecological breeding mode is the best,which is class Ⅰ.water.Comprehensive recycling water and non-recycling water Heosemys grandis breeding water body quality evaluation and growth,economic benefit analysis results,recirculating water aquaculture model aquaculture water quality in line with fishery water standards and Heosemys grandis grow better,more economical,although the water quality of the culture is not non-The recirculating aquaculture model is good but does not discharge the culture wastewater to the outside causing environmental pollution.Under the experimental conditions,the circulating aquaculture model and the original ecological model are recommended. |
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