适宜牡蛎与龙须菜配比提高含氮养殖废水处理效果

水产养殖废水中含有大量的N、P等营养素,不加处理的排放将带来环境污染,通过养殖废水的资源化利用,可以保护环境,同时获得经济效益,促进水产养殖业可持续发展。该文研究了太平洋牡蛎(Crassostrea gigas)与龙须菜(Gracilaria lemaneiformis)处理大西洋鲑(Salmo salar)养殖废水的适宜养殖密度与数量配比。研究内容分为两部分:1)龙须菜试验。探讨不同龙须菜养殖密度(0.8、1.6、2.4和3.2 g/L)对大西洋鲑养殖废水氮素的去除效果,结果表明,龙须菜湿质量为2.4 g时对大西洋鲑养殖废水有较好处理效果,其中TAN、NO2-N、NO3-N的最高去除率分别为59.20%、62.16%和21.77%。2)牡蛎和龙须菜混养试验。试验中牡蛎(软体部湿质量)、龙须菜(湿质量)密度均为1.6、2.4、3.2 g/L。结果表明,牡蛎2.4 g/L、龙须菜2.4 g/L组合对废水中的NO2-N去除率达40.29%;牡蛎、龙须菜对TAN的去除存在交互作用,且龙须菜影响效应较大,2.4 g/L龙须菜对TAN去除率最高达74.44%;牡蛎2.4 g/L、龙须菜1.6 g/L时对NO3-N去除效果好,但与龙须菜密度2.4 g/L时无显著性差异。综合分析确定二者密度均为2.4 g/L,即牡蛎与龙须菜密度比为1:1时处理效果最佳。

Optimal ratios of oyster to Gracilaria improving removal efficiency of nitrogen nutrients in aquaculture wastewater

Abstract: Currently, intensive marine aquaculture has been widely adopted to obtain higher yields of aquatic food production. However, the effluent unfiltered wastewater, including organic and inorganic nitrogen and phosphorous can damage the physiology of farmed species and cause hyper-trophication of adjacent ecosystems. Using bivalve mollusc and macroalgae to purify wastewater before discharged is gaining extensive attention due to their cost effect and efficient features. The present study was conducted to investigate the effectiveness of an oyster-Gracilaria system. The study focused on the effects of Gracilaria lemaneiformis densities and Crassostrea gigas to Gracilaria lemaneiformis ratios. This experiment contained two parts. In the first part, four densities of Gracilaria (0.8, 1.6, 2.4 and 3.2 g/L) were set up. The results showed that all the four treatments had a low total ammonia nitrogen removal rate (less than 40%) before 48 h. However, treatments of 2.4 g/L and 3.2 g/L had a relative high TAN removal rate in 60 h (54.34% and 67.70%, respectively), 72 h (39.77% and 48.27%, respectively). Gracilaria of 1.6 g/L and 2.4 g/L removed relative more NO2-N in 6 h (56.64% and 55.26%), and in 12 h. In comparison, 2.4 g/L had a significant higher (P<0.05) NO2-N removal rate (57.33%) than other groups. Significant difference (P<0.05) of NO3-N removal rate occurred in 6, 18 and 72 h, with the highest removal rate in sets of 3.2 g/L (11.72%), 2.4 g/L (15.65%) and 2.4 g/L (7.61%), respectively. In the second part, a two-factor experiment was designed. Three gradient densities of oyster (1.6, 2.4, 3.2 g/L) and Gracilaria were set up and combined to each other. Results showed that 2.4 g/L oyster and 2.4 g/L Gracilaria lemaneiformis combination had higher NO2-N removal rate (40.29%) than other treatments. There were significant (P<0.05?) interaction on TAN removal efficiency between the densities of oyster and Gracilaria lemaneiformis and Gracilaria lemaneiformis played a leading role (Gracilaria of 2.4 g/L removed 74.44% of TAN). The combination of 2.4g/L oyster and 1.6g/L Gracilaria lemaneiformis had better NO3-N removal rates, while there was no significant (P>0.05) difference with Gracilaria lemaneiformis of 2.4 g/L. Therefore, both oyster and Gracilaria lemaneiformis had the best efficiency in treating wastewater at the density of 2.4 g/L (Oyster: Gracilaria=1:1).