Blackish rainwater during haze: Is tap water still safe to drink? Grace Fu answers

Between Oct 5 and 18, Singapore experienced a run of poor air quality , with the 24-hour Pollutant Standards Index (PSI) remaining in the unhealthy to very unhealthy range.

And during that period, some residents in Singapore took to social media to share how rainwater collected in their pails were blackish grey , sparking discussions on whether drinking water may be affected.

@asiaone While many thought that the heavy rain around Singapore on Thursday (Oct 15) morning would help "wash away" the haze, the resulting grey rainwater sparked concern among some locals. #sgnews #Singapore #Haze #Pollution ♬ original sound - AsiaOne

To address these concerns, Minister for Sustainability and the Environment Grace Fu took to social media recently to share about Singapore's water treatment process and to answer the question of whether drinking water is safe.

Rainwater during haze more acidic

Sharing water sampling results collected from rainwater in Kranji, Ulu Pandan, runoff from Yew Tee, and tap water, the minister noted that rainwater collected during hazy conditions may be slightly more acidic and contain higher levels of particles and organic matter.

She shared that she visited Singapore's national water agency PUB's Water Quality Laboratory then.

According to the results of the samples collected on Oct 17, when the PSI reading was 193, rainwater had a pH value of 5.7, while rainwater collected when PSI was moderate had a pH value of 6.6.

Meanwhile, rainwater collected on a normal day and treated water had a pH value of 6.8 and 7.8 respectively.

A lower pH means the water is more acidic, while a higher pH means more alkaline water.

Explaining this, Fu said that this is expected as rainwater can pick up airborne particles and substances as it passes through the atmosphere.

She added that the extent of discoloration, or how 'blackish' it looked, depended on whether the rainwater was collected directly or from runoffs.

Not for cooking, personal use

But regardless of whether there is haze, rainwater collected should not be used for cooking, drinking, or personal hygiene, the minister emphasised.

She pointed out that water collected in Singapore's reservoirs go through several stages of treatment to remove dirt, tiny particles, and other impurities.

"Our water treatment processes can filter out particles up to 100 times smaller than PM2.5. Rest assured that the PM2.5 haze particles will be removed during this comprehensive treatment process."

But PUB, has still stepped up checks on the country's water quality during this period, the minister said.

She noted that the agency's tests have not found any unusual change in treated water quality.

"So, while the blackish water seems worrying, our tap water remains clean and safe to drink. PUB will continue to monitor water quality in Singapore," Fu said.

10 月 5 日至 18 日期间，新加坡空气质量持续恶化，24 小时污染物标准指数 (PSI) 一直处于不健康到非常不健康的范围内。

在此期间，新加坡的一些居民在社交媒体上分享了他们桶里收集的雨水呈黑灰色的情况，引发了关于饮用水是否会受到影响的讨论。

@asiaone 虽然许多人认为周四（10月15日）上午新加坡的强降雨有助于“冲刷”雾霾，但雨后灰蒙蒙的雨水却引发了一些当地居民的担忧。#sgnews #Singapore #Haze #Pollution ♬ original sound - AsiaOne

为了消除这些疑虑，新加坡永续发展及环境部长傅海燕近日在社交媒体上分享了新加坡的水处理流程，并回答了饮用水是否安全的问题。

雾霾期间的雨水酸性更强

部长分享了从克兰芝、乌鲁班丹的雨水、油池的径流和自来水中采集的水样检测结果，并指出在雾霾天气下收集的雨水可能酸性稍强，且含有较高水平的颗粒物和有机物。

她透露，当时她参观了新加坡国家水务局（PUB）的水质实验室。

根据 10 月 17 日采集的样本结果，当 PSI 读数为 193 时，雨水的 pH 值为 5.7；而当 PSI 处于中等水平时采集的雨水的 pH 值为 6.6。

同时，正常情况下收集的雨水和处理后的水的 pH 值分别为 6.8 和 7.8。

pH值越低，水的酸性越强；pH值越高，水的碱性越强。

傅解释说，这是意料之中的，因为雨水在穿过大气层时会带走空气中的颗粒物和物质。

她补充说，变色的程度，或者说看起来有多“发黑”，取决于雨水是直接收集的还是来自径流的。

非烹饪用途，仅供个人使用

但部长强调，无论是否有雾霾，收集的雨水都不应用于烹饪、饮用或个人卫生。

她指出，新加坡水库中收集的水要经过多个处理阶段，以去除污垢、微小颗粒和其他杂质。

“我们的水处理工艺可以过滤掉比PM2.5小100倍的颗粒物。请放心，在这一综合处理过程中，PM2.5雾霾颗粒物将被去除。”

但这位部长表示，在此期间，公用事业局（PUB）仍然加强了对该国水质的检查。

她指出，该机构的测试并未发现处理后的水质有任何异常变化。

“所以，虽然水呈黑色看起来令人担忧，但我们的自来水仍然干净安全，可以放心饮用。公用事业局将继续监测新加坡的水质，”傅先生说。