进出水方式对高负荷浅层渗滤净化生活污水效果的影响

Impact of Loading and Draining Conditions of On-Site Subsurface Infiltration Systems With High Hydraulic Loading Rate on Purification of Domestic Wastewater

为研究农村分散住户用水不均匀和排放泵井运行不连续条件下高负荷地下浅层渗滤系统的净化效果,建立渗滤试验柱,以实际生活污水为进水,在12.5 cm.d-1日均水力负荷下,比较连续进水、间歇进水和自由排水、间歇排水对实际生活污水净化效果的影响。结果表明,各渗滤柱对NH4+-N的平均去除率均大于96%。对COD的平均去除率为41.2%～67.7%,其中采用间歇进水、间歇排水方式的渗滤柱去除率最低,但出水仍可达到GB8978—1996《污水综合排放标准》中二级标准。各渗滤柱对TN的平均去除率为17.5%～37.2%,其中采用间歇进水、间歇排水的渗滤柱平均去除率最高,表明强化反硝化作用是提高脱氮效率的主要途径。对TP的平均去除率为51.0%～78.0%,其中采用连续进水、间歇排水的渗滤柱平均去除率最高,表明延长污水停留时间、增加与填料的接触面积能增强对TP的去除效果。间歇进水、间歇排水方式下,渗滤柱对COD的去除效果有所下降,但是对N、P营养盐的综合去除效果最好。

In order to investigate purification efficiency of the high-loading shallow underground infiltration system under the conditions of uneven influx of domestic sewage from widely scattered farm households and intermittent operation of the drainage pumps,4 350 mm-tall infiltration columns were built up for an experiment to compare different loading and draining modes in effect of purifying domestic sewage with a daily hydraulic load of 12.5 cm·d-1.The experiment was designed to have four different loading and draining modes,that is,continuous loading,intermittent loading,free draining and intermittent draining.Results show that the average NH＋4-N removal rates of all the columns were over 96%,and the average COD removal rates of the columns were in the range of 41.2%-67.7%.Of the four,intermittent loading and intermittent draining was the lowest in removal rate,but their drainages still met Grade II criteria of the National Standard GB 8978—1996 ＂Integrated Standard for Drainage of Wastewater＂.The average TN removal rates of the columns were 17.5%-37.2%.The modes of intermittent loading and intermittent draining were the highest in TN removal rate,suggesting that to enhance nitrification/denitrification is the main way to increase N removal rate.The average TP removal rates of the four columns were in the range of 51.0%-78.0%.The columns of continuous loading and intermittent draining were the highest in TP removal rate,suggesting that to prolong stay of the wastewater in the column and to expand area of the contact surface between the wastewater and the filler are effective to increase P removal rate.the modes of intermittent loading and intermittent draining decreased COD removal rate,but were the most effective in removing N and P nutrients from wastewater.