污水的土壤渗滤法处理工艺运行与模拟研究

【作者】 张之崟；

【导师】 雷中方；

【作者基本信息】 复旦大学 ， 环境工程， 2008， 硕士

【摘要】 土壤渗滤法是一种充分利用土壤中的动物、植物、微生物以及土壤的物理、化学特性的污水就地处理技术。本课题通过现场试验与实验室模拟相结合,旨在研究不同工况条件下的运行效果,根据碳、氮、磷去除效果的影响因素和去除机理,建立反应动力学模型,并探讨最佳的工艺设计和运行条件,提出工艺运行中的保障措施。现场试验结果表明,土壤渗滤系统经过3个月的启动调试后逐渐成熟。“太阳能曝气-沉淀”的预处理工艺起到初步降解有机物的作用,其去除率低于35.2%。各工况条件下系统最终出水的化学需氧量（COD）浓度均小于40 mg l^-1,总去除率为50.6%～75.8%,其中水温是影响COD总去除率的一个主要因素。总磷（TP）、酚类和邻苯二甲酸酯类物质的去除率分别达到57.7%～100.0%、35.2%～100.0%和36.4%～59.6%。溶解氧提高为进水的1～3倍、UV₂₅₄下降了13.5%～67.2%,有利于水生生物生存、繁衍以及生态系统的恢复。实验室试验结果表明,除温度的影响以外,复合土壤的组成及本身的理化性质、废水的水质情况、水力负荷、土壤层有效高度等都会影响碳、氮、磷的去除效果。其中,复合土壤本身的性质对COD和TP去除效果的影响最大;随着复合土壤碳氮比的增大,反硝化作用也会显著增强。废水的水质情况是影响总氮（TN）去除效果的最主要因素;而在高浓度COD和TP进水条件下,各自出水始终能够维持在较低范围内。水力负荷对COD和TP去除效果的影响不大;但是高水力负荷比低水力负荷对TN去除的影响更大。较高的水力负荷还会引起硝态氮（NO₃^--N）和亚硝态氮（NO₂^--N）出水浓度剧增,本研究中土壤渗滤系统的最佳水力负荷为8.0×10^-2 m³ m^-2 d^-1。0.50 m的土壤层有效高度完全可以满足去除COD的需要;但并不足以保证完全的反硝化进程和TP的高效去除。另外,土壤渗滤系统对氨氮（NH₄⁺-N）的吸附作用很强,去除率受到以上因素的影响很小。各污染物去除机理的研究表明,COD的降解包括非生物吸附和生物降解作用,其中非生物吸附过程满足Temkin吸附等温式,生物降解作用占COD总去除率的57.7%～71.9%。NH₄⁺-N的非生物吸附和生物降解作用所占比重因进水浓度的高低而异;NO₂^--N的积累和不足均会影响硝化反应进程,其出水浓度应尽量控制在0.10 mg l^-1～0.25 mg l^-1范围内;土壤碳氮比是反硝化作用的限制性因素。TP的静态吸附过程满足Freundlich吸附等温式,氢氧化合物铁（Fe₀）的含量与TP去除率之间存在很大的相关性。以Eckenfelder一级反应动力学模型为基础,通过添加或修正温度、水力负荷、进水浓度、土壤层有效高度和复合土壤性质等影响因素项,建立COD、TN和TP的去除模型,可以预测土壤渗滤系统的出水水质,模拟值与实测值的误差可以分别控制在5 mg l^-1、5.0 mg l^-1和0.15 mg l^-1以内。从模型的角度分析,系统降解能力的极限值是决定COD去除率的关键,水力负荷对TN和TP出水浓度的影响很大。另外,通过对上述关键因素的调控,土壤渗滤系统对污染物的去除效果可以明显提高。更多还原

【Abstract】 Soil Infiltration Treatment （SIT） is a kind of in-situ wastewater treatment technique, making full use of animals, plants, microorganisms in soil and the physico-chemical characteristics of soil. The purpose of this thesis was to focus on the purification performance under different operation conditions through both field and laboratory experiments. The kinetics models were established according to the influence factors on carbon, nitrogen and phosphorus removals and their removal mechanisms. At last, the optimal parameter designs and operation conditions were proposed for the guarantee of effective performance.The results from field experiments showed that SIT systems became gradually maturation during the first 3 month start-up periods. The pretreatment process including solar energy aeration and sedimentation could remove less than 35.2 % of organics. All the final effluent CODs were less than 40 mg l^-1 under various conditions with accumulative COD removal rates ranged from 50.6 % to 75.8 %., on which water temperature was one of the important factors. The removal rates of total phosphorus, phenolic and phthalate pollutants could reach 57.7 %-100.0 %, 35.2 %-100.0 % and 36.4 %-59.6 %, respectively. And the effluent DOs were 1-3 times of the influent values with UV254 decreased by 13.5 %-67.2 %, which was in favor of the survival and procreation of hydrophilous creatures and the recovery of ecosystem.The results from laboratory experiments demonstrated that besides temperature, the constituent and physico-chemical characteristic of artificial soil, wastewater quality of the influent, hydraulic loading rate and effective depth of soil layer, etc. affected carbon, nitrogen and phosphorus removals. The characteristic of artificial soil was the most important factor on COD and TP removals, and the denitrification process was remarkably improved with the increase of C:N ratio in artificial soil. Wastewater quality was the most important factor on TN removal but the impact of it on COD and TP removals seemed rather less. So did the hydraulic loading rate. From the experiment results, an optimal hydraulic loading rate, 8.0×10^-2 m³ m^-2 d^-1 was obtained. The effective depth of soil layer of 0.50 m could be satisfied with COD removal, but not enough for denitrification and higher TP removal requirements. In addition, the removal of ammonia nitrogen was not affected by the above influence factors due to the large adsorption capability of soil matrix applied.The researches on pollutant removal mechanisms disclosed that COD removal consisted of abiological adsorption and biodegradation processes. The abiological process followed Temkin adsorption isothermal, and the proportion of biological COD removal occupied 57.7 %-71.9 %. The abiological and biological removals of ammonia nitrogen changed with the variance of influent concentration. Both accumulation and shortage of nitrite nitrogen could affect nitrification efficiency and the effluent nitrite concentrations should be controlled within 0.10 mg l^-1-0.25 mg l^-1 with the consideration of maintaining the sustainable operation of SIT. The results indicated that C:N ratio in artificial soil was the limiting factor on denitrification. And the static adsorption of TP followed Freundlich isothermal, in which Fe oxyhydroxide （Fe_o） content had a close relationship with TP removal rate.Based on Eckenfelder first order kinetic model, COD, TN and TP removal models were established by adding or modifying several influence factors, for example, temperature, hydraulic loading rate, influent concentration, effective depth of soil layer and the characteristic of artificial soil, etc. These models could be used to forecast the effluent COD, TN and TP concentrations from SIT systems, with the errors between simulated and experimental values less than 5 mg 1^-1、5.0 mg l^-1 and 0.15 mg l^-1, respectively. The results implied that COD removal rates were determined by the removal potential of SIT system. Besides, the simulation resutlts indicated that TN and TP effluent concentrations were significantly affected by hydraulic loading rate. Furthermore, the pollutant removal efficiencies of SIT systems could be remarkably improved by optimizing these key factors mentioned above.更多还原