sewage disposal

例句：

1. 1. The cityhas invested heavily in sewage treatment plants to improve the quality of its water supply.
   该市已大力投资于污水处理厂，以改善其供水质量。
2. 2.The wastewater from the factories needs to be properly disposed of to prevent pollution.
   工厂产生的废水需要妥善处理，以防止污染。
3. 3.The sewage disposal system is designed to treat and recycle wastewater for reuse.
   污水处理系统旨在处理和回收废水，以便重复使用。