挥发性硅氧烷在恒水位序批式活性污泥法市政废水处理厂的归趋及生态风险评估

发布时间：2018-02-26 05:13

  本文关键词： 挥发性硅氧烷 恒水位序批式活性污泥法 逸度模型 质量流量 生态风险评估　出处：《大连海事大学》2015年硕士论文　论文类型：学位论文

【摘要】：本文主要对恒水位序批式活性污泥法(CWSBR)为核心工艺的废水处理厂中的环状和线性挥发性甲基硅氧烷(VMSs)迁移、分布的归趋变化展开研究,并对其出水水质的生态风险进行评估。我们采集一周时间内的废水处理厂进水、出水和污泥样品,实验测得其环状VMS的平均浓度分别为1.053 μg L-1和0.343μg L-1,总去除效率为67.4%。由于较高的固-水分配系数(Kd),使得污泥样中的VMSs浓度较高,平均值为4.876 μg g-1。并计算得到该废水处理厂的每日质量流量较稳定,周末和工作日的流量及浓度对比均表现为波动不大,在废水处理厂服务范围内,总VMSs的预计人均质量负荷为每1000人口145-236 mg d-1,平均为195 mg d-1。为了进一步阐明VMSs的去除机制,建立CWSBR逸度模型来模拟典型环状VMS八甲基环四硅氧烷(D4)、十甲基环戊硅氧烷(D5)和十二甲基环己硅氧烷(D6)的去除途径。模型结果得69%的D4、24%的D5和9%的D6通过曝气反应和表面挥发进入到大气中,其中曝气是一个主要的方式；而另外17%的D4、45%的D5和54%的D6则吸附至剩余污泥中。综合实验和模型结果表明,污泥吸附和挥发是影响VMS在该恒水位序批式活性污泥法市政废水处理厂中归趋变化的关键因素,随着环状VMS分子量的增大和疏水性的增强,污泥吸附能力逐渐增强而挥发性则下降。采用蒙特卡洛模拟进行不确定性分析和敏感性分析,得出出水总悬浮固体浓度、混合液相悬浮固体浓度、剩余污泥流量和进水流速是对VMSs质量分布影响最大的因素。同时实验结果可能会受到居民护肤品和化妆品使用习惯的周期性模式影响,需要长期对废水处理厂进行监测以获得数据支持。生态风险评估表明,该CWSBR市政废水处理厂排放的含有D4、D5和D6的出水风险商在0.1≤HQ0.5间,未对周围水生生态系统构成危害,但仍需要进行不定期动态监测,减少高危害、高风险发生的几率。
[Abstract]:In this paper, the migration and distribution of cyclic and linear volatile methyl siloxane (VMSs) in a wastewater treatment plant with constant water level sequential batch activated sludge process (CWSBR) as the core process were studied. And to assess the ecological risk of the effluent quality. We collected the influent, effluent and sludge samples from the wastewater treatment plant within one week. The average concentrations of cyclic VMS were 1.053 渭 g L-1 and 0.343 渭 g L-1, respectively, and the total removal efficiency was 67.4%. Because of the high solid-water partition coefficient (KDX), the concentration of VMSs in sludge samples was higher. The average value was 4.876 渭 g g-1.The results showed that the daily mass flow of the wastewater treatment plant was stable, and the flow and concentration of the wastewater treatment plant fluctuated little on weekends and weekdays, and were within the service range of the wastewater treatment plant. The estimated per capita mass load of total VMSs is 145-236 mg d-1 per 1,000 population, with an average of 195mg d-1.In order to further clarify the mechanism of VMSs removal, CWSBR fugacity model was established to simulate the removal pathways of typical cyclic VMS octamethylcyclotetrasiloxane (D4), decamethylcyclopentylsiloxane (D5) and 12 methylcyclohexane siloxane (D6). The results of the model showed that 69% of D424% of D5 and 9% of D6 were subjected to aeration reaction. And surface volatilization into the atmosphere, Aeration is one of the main methods, while the other 17% D4N 45% D5 and 54% D6 are adsorbed to the excess sludge. Sludge adsorption and volatilization are the key factors that affect the fate of VMS in the municipal wastewater treatment plant with constant water level sequencing activated sludge process. With the increase of molecular weight and hydrophobicity of cyclic VMS, the adsorption and volatilization of sludge are the key factors. The adsorption capacity of sludge increased gradually but the volatility decreased. The uncertainty analysis and sensitivity analysis of Monte Carlo simulation were used to obtain the total suspended solid concentration of effluent and the concentration of mixed liquid suspension solid. Excess sludge flow and influent flow rate were the most important factors affecting the quality distribution of VMSs. Meanwhile, the experimental results may be influenced by the periodic patterns of skin care products and cosmetics usage habits. Long-term monitoring of wastewater treatment plants is required to obtain data support. The ecological risk assessment shows that the effluent risk quotient containing D4N D5 and D6 discharged from the CWSBR municipal wastewater treatment plant is 0.1 鈮，

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