Sewage sludge which mainly comes from the primary settling tank and discharge of surplus sludge is the deposit produced in each operating unit in municipal wastewater treatmentplant.
城市污泥是城市污水处理厂经各级处理净化污水而产生的沉积物，主要来自初沉池和剩余污泥的排放。
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BOT as one kind of invest and financing mode in municipal construction, has been widely applied in the construction municipal sewage treatmentplant, but lacks of completed rules and laws now.