给水管壁松散沉积物的形成与脱落规律研究

Formation and Detachment of Loose Sediments from Drinking Water Distribution System

给水管壁松散沉积物的脱落是造成管网水质问题的一个重要原因,但目前国内外对管壁松散沉积物的研究还不够系统。利用管道试验反应器模拟实际给水管网,研究不同水力条件下松散沉积物的形成与脱落规律,并分析松散沉积物的化学特性。结果表明,水中的颗粒物附着在给水管壁上会形成松散沉积物,其成分包括有机物和无机物,有机物量占3.59%(以TOC计),其余为无机物,其中Ca CO3(32.26%)、Si O2(14.51%)、Fe OOH(10.42%)和Al(OH)3(6.43%)的占比较大。松散沉积物具有易形成、易脱落的特点,当管壁处的剪切力<0.33 Pa时,管壁均有松散沉积物形成;当剪切力>0.94 Pa时,松散沉积物脱落比较完全。给水管网中水流速度的急剧增大易引起松散沉积物的脱落,应合理均衡配置各时段的用水量,使水流速度尽量保持恒定;若流速长时间处于较低水平,需要提高流速时应该逐步、缓慢进行。

The detachment of loose sediments from pipe wall is one of the main reasons for water quality problems of drinking water distribution system. Nowadays, the research on loose sediments is still not systematic at home and abroad. Formation and detachment of loose sediments under different flow conditions were studied using a simulative in-pipe reactor. The chemical characteristics of loose sediments were analyzed. The results showed that loose sediments were composed of particles in water which were adhered to pipe wall, and they were mainly inorganic compounds including CaCO3 of 32.26%, SiO2 of 14.51% FeOOH of 10.42% and A1 （OH）3 of 6.43% with organic compounds of 3.59% （calculated as TOC）. Loose sediments were easy to form and detach. When pipe-wall shear stress was smaller than O. 33 Pa, there would be the loose sediments formed on the wall; while pipe-wall shear stress was bigger than 0.94 Pa, most formed loose sediments could be washed out. Sharp increase of in-pipe flow velocity could easily lead to the detachment of loose sediments, so water consumptions during various periods should be reasonably and evenly allocated in order to keep the flow velocity as constant as possible. If the flow velocity stayed slow for a long time and needed to be increased, the procedure should be conducted gradually.