Contamination of water supplies is usually due to poor sanitation close to water sources, sewage disposal into the sources themselves, leakage of sewage into distribution systems or contamination with industrial or farm waste.

leakage ^{n. [U and C] when gas, water etc. leaks in or out, or the amount of it that has leaked 泄露}

• Minimize probability of data leakage. ^{最大程度地减少出现数据漏洞的可能。}
• Leakage and removal. ^{泄露和消除。}
• Coolant system leakage, secondary failure. ^{冷却剂系统的泄露，次级失效。}
• When you drill offshore, you always have leakage. ^{当你在海上钻井，总会有泄漏发生。}
• The public works department is responsible for preventing the leakage of sewage into the streets.^{公共工程部门负责防止污水渗漏到街道中。}

distribute ⇒ distribution ^{n.分/销/发/配，配送}

• As administrative overheads rise, so the earnings of the business after meeting the expense of administration, will fall; and the business will have less money to distribute as dividends or invest directly in its future progress and development.
• Some of the victims are complaining loudly about the uneven distribution of emergency aid. ^{一些受害者正大声地抱怨紧急援助的不均衡分配。}
• How do I know its charge distribution? ^{我怎么知道它的电荷分布呢？}

with ^{prep. because of  因为}

• She was shivering with cold.
• My hands are rough with work.
• Anna was scarcely able to stand with exhaustion.

waste ^{n. [U] unwanted materials or substances that are left after you have used something 垃圾，废料}

• The local council has introduced new bins to encourage the recycling of household waste. ^{当地委员会引入了新垃圾桶以鼓励生活垃圾的回收。}
• Strict laws prevent factories from dumping industrial waste into the nearby river. ^{严格的法律禁止工厂将工业废物排入附近的河流。}
• Specialized containers are required for the safe transport of hazardous chemical waste. ^{安全运输危险化学废物需要专门的容器。}

contamination of... ^…的污染

• The company was fined heavily for the contamination of the local river.^{该公司因污染当地河流而被重罚。}
• The soil contamination of the farmland made it unsuitable for growing crops.^{农田的土壤污染使其不适合种植农作物。}

be due to sth. ^{是由于/归因于}

• The cancellation of the flight was due to severe weather.^{航班的取消是由于恶劣的天气。}
• His success is largely due to his perseverance.^{他的成功很大程度上归因于他的毅力。}

Even if a piped water supply is safe at its source, it is not always safe by the time it reaches the tap.

pipe ^{v. to send a liquid or gas through a pipe to another place 用管道输送}

• villages with no piped water
• Eighty per cent of sewage is piped directly into the sea. 

piped water supply ^{管道供水/自来水供应}

• The village finally got access to a reliable piped water supply.^{这个村庄终于获得了可靠的管道供水。}
• The new development includes an underground piped water supply system.^{这个新的开发项目包括一个地下管道供水系统。}

… by the time when / that / at which it reaches the tap. ^{定语从句省略关系代词}

by the time... ^{等到…的时候}

• By the time we arrived at the station, the train had already left.^{等到我们到达车站的时候，火车已经离开了。}
• You must finish the report by the time the manager returns from her trip.^{你必须在经理出差回来的时候完成报告。}

Intermittent tap-water supplies should be regarded as particularly suspect.

intermittent ^{(adj.) 间歇性的/断断续续的}

• The patient experienced intermittent fever throughout the night.^{患者整晚都有间歇性的发烧。}
• We are having trouble with an intermittent signal from the satellite.^{我们正面临着来自卫星的间歇性信号问题。}

be regarded as + adj. ^{被视为/被认为是(形容词做宾语，省略了being)}

• The old treaty is no longer regarded as legally binding.^{这份旧条约不再被视为具有法律约束力。}
• His early work is widely regarded as his most influential.^{他的早期作品被广泛认为是他最具影响力的。}

suspect ^{(adj.) 可疑的/不可信的}

• …, or the sheriff made suspect by vicious gossip; …
• The police found a suspect package outside the embassy.^{警方在大使馆外发现了一个可疑包裹。}
• He gave a rather suspect explanation for his absence yesterday.^{他对昨天的缺席给出了一个相当可疑的解释。}