最近去了一趟昆明附近某个镇的水厂,他们正在更换滤池的滤料。原来用的无烟煤、石英砂双层滤料,这次不用了,改用了云南生产的人工砂(单一)滤料。据说换过后,“效果”差不多,而且投资比较省。我想“投资”比较省,不能只看目前的开支。至于说到“效果”,我想要运转一段时间后才看 Recently I went to a water plant in a town near Kunming, where they were changing filter media. The original anthracite, quartz sand double filter, this time no need to switch to the production of artificial sand in Yunnan (single) filter. It is said that after the change, “effect” is similar, and the investment is more provincial. I want to “invest” more provincial, can not just look at the current expenditure. As for the “effect”, I want to run for some time before looking