Water color becomes henna from gray and back. Using microbial flocculation does not cause second pollution and the cost of water treatment declines greatly.

SS去除率达到88% ，水的颜色由灰黑色变成红褐色液体，更为重要的是微生物絮凝剂无二次污染，且吨水处理的成本大大降低。

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The city has proposed a number of water treatment and conservation projects the cost of which raises water bills high enough so that even environmentalists are beginning to raise alarms.

该市已经提出了一系列的水资源处理和保护项目，这些项目的成本大大提高了水费，以至于连环保人士也开始发出警告。

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"It's one of the most cost-effective water treatment systems in the world," he says.

“这是全世界最省钱的净水系统之一，”他说。

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Human societies will thus continue to search for new sources of water, but the cost of procuring water is a function of the combined cost of extraction, harvesting, transportation, treatment, storage, and delivery.

UNESCO: Natural Sciences