泡沫分离技术在水产养殖水处理中的应用

在水质净化处理中,泡沫分离法有其独特的功能,它能将溶解性有机物及悬浮物通过气泡的吸附形成泡沫被去除,适用于集约化水产养殖中闭合循环水处理。本文借鉴目前国际、国内这方面的研究资料,对泡沫分离技术的原理、器械结构类型、功效以及设计参数等作了系统阐述,以利该项技术的完善和加快应用     

佛山水道疏浚底泥处置方案选择

疏浚底泥的不同处置方案各有优缺点,在选用污泥处理处置工艺时,要综合考虑环境安全、资源投入产出和收益影响,比从而实现环境、社会和经济效益最大化。其中,环境安全应该是最优先考虑的问题。根据佛山水道底泥重金属含量的分析结果,佛山水道底泥重金属污染严重,超过了污泥农用控制标准值,疏浚底泥农田综合利用不可行;但底泥毒性浸出实验结果显示,佛山水道各采样点底泥浸出液中重金属含量远低于危险废物标准限值,不属于危险废物,可以对其进行卫生土地填埋。     

Accumulation of phytotoxic organic acids in reused nutrient solution during hydroponic cultivation of lettuce (Lactuca sativa L.)

Proper nutrient solution management in the root zone is the first consideration for the adoption of a closed hydroponic system. Plant roots often exude numerous organic acids, which are known to inhibit growth. To investigate the accumulation of these phytotoxic organic acids as root exudates, lettuce (Lactuca sativa L.) was hydroponically grown in reused nutrient solution. Organic acids were extracted with diethyl ether from the reused nutrient solutions (RNS), root residues, and activated charcoal (AC) then quantified by GC/MS. Five individual organic acids were identified from the root residues and seven from the reused nutrient solutions. After 90 days of lettuce cultivation, in the treated AC in 3RNS, benzoic, phenylacetic, cinnamic, p-hydroxybenzoic, lauric, phthalic, vanillic, palmitic, and stearic acids were identified. In contrast, little or no organic acids were detected in the 3RNS treated with AC (3RNS/AC). Artificially applied pure organic acids ranging from 25 to 200 μM inhibited lettuce growth in a concentration-dependent manner. Lettuce growth was also greatly reduced in the nutrient solutions containing a externally applied, simulated mixture of the organic acids as in the 3RNS. Lettuce growth was not inhibited following the addition of AC (2.5 g/L) to the nutrient solution containing the mixture of organic acids. Our results demonstrated that organic acids were accumulated in reused nutrient solutions and were phytotoxic to lettuce growth. Also, this study showed that the addition of AC reduces the phytotoxic effects by eliminating the organic acids.     

Wetting agent effect on physical properties of new and reused rockwool and coconut coir waste

Wettability of growing medium in horticulture is an important practical factor of this industry. With a proper choice and a right application, wetting agent in the nutrient solution would improve wettability and some other physical properties of growing media. The aim of this study was to evaluate the effects on some physical properties of new and reused rockwool and coconut coir dust substrates with different doses of wetting agent (2, 10, 20, 100, 200, 1000, 2000, 10,000 and 20,000 mg L⁻¹) applied to the nutrient solution and their effects measured by using bioassays. The wetting agent was ether poly-ethylene-glycol nonil-phenol with 20% (w/v) as an active ingredient of a non-ionic surfactant. Bioassay results showed differences among species. For this, the method can be suggested as a good tool to be utilized through fertigation in soilless crops; however, other studies should be proposed for each species in particular. Except to the 2 mg L⁻¹ wetting agent content in reused coir waste, the total water-holding capacity increased with the wetting agent. With 2 mg L⁻¹ wetting agent content there was an important and significant increase the easily available water (over 600%) in both substrates (including the reused ones), while higher doses show no significant differences. The effect of adjuvants added through fertigation is directly dependant on the substrate type evaluated. The substrate reutilized after one crop, reduces the air capacity and increases the easily available water and total water-holding capacity. 2 mg L⁻¹ is the wetting agent concentration more adequate in coir waste and rockwool.