WAT ER YOU DRINKING? : Tapping into Shanghai’s Water Secrets

Tapping into Shanghai’s Water Secrets


I recently read an article in the news, ‘2,800 Pigs Dumped in Shanghai River Raises Concern’, which lead to me questioning the pollution levels in Shanghai’s waters. Living in Shanghai, everyday I face a dilemma I always found to be rather minimal, whether or not to drink the water from the tap or to not be lazy and climb the four flights of stairs down to the nearest bottled water dispenser. As I had previously lived in countries such as England, and Japan, where clean water is abundantly available from taps, I assumed that Shanghai’s tap water could not have a large concentration of pollutants within its waters. I used to drink water in Shanghai from the tap, arguing that if anything, the exposure to these unknown particles would harden my immune system, like a child playing in the soil.


About 80% of the water we get in Shanghai is from the Huangpu River. The remaining 20% comes from the Yangtze River. On the list of the most polluted rivers in the world, the Yangtze and the Huangpu are both mentioned, with the Yangtze River Water Resources Commission report noting the total volume of sewage emptied into the Yangtze river totaling approximately 20 million tons. Noteable pollutants within the Shanghai river water are chlorine, heavy metals such as lead, nitrates and bacteria. (WHO, 2011)


Chlorine, a highly efficient disinfectant, is added to water for cleaning purposes, “Chlorine has been hailed as the savior against cholera and various other water-borne diseases, and rightfully so,” says Steve Harrison, president of water filter maker Environmental Systems Distributing. “Its disinfectant qualities…have allowed communities and whole cities to grow and prosper by providing disease-free tap water to homes and industry.” (About.com, 2010) However, Chlorine is defined by the American journal of Public Health to cause “significant increases in certain types of cancer, asthma and skin irritations” (American Journal of Public Health, 2011) . When combined with organic matter found in rivers, chlorine undergoes a chemical reaction to form products such as trihalomethanes (THMs) which is are known carcinogens (a substance capable of causing cancer in living tissue). Chlorine converts chemically by replacing three of the four hydrogen atoms of methane (CH4) with chlorine halogen atoms to produces these THMs. Due to the high levels of bacteria caused by improper dumping of sewage and other biological contamination, Chinese departments of water works simply use more chlorine.


Similarly to chlorine, lead is also extremely dangerous as it is toxic even in the amount of micrograms when entering the body, and leads to higher blood pressure, kidney dysfunction, anemia and colon cancer in adults. Nitrates found in the river water enter through organic runoff such as through fertilizers. These nitrates entering the readily available tap water can be fatal to children under the age of six months, as they cannot perform the chemical process shown below in their stomachs to convert nitrites into nitrates. (Sigler, 2010)


2NO2(g) + 2OH(aq) –> NO3(aq) + H2O(l) + NO2(aq)


If nitrites are not converted into nitrates, this poses a problem as in the early stage of development, nitrite reacts with hemoglobin, which is responsible for the transfer of oxygen, and prevents this transport. Evidently, the effect of this is a decreased oxygen supply to the body, well known as blue baby syndrome (or methemoglobinemia). Nevertheless, it should be known that this condition is very rare.(WHO, 2011)


I believed that by simply boiling Shanghai’s water, it would be safe to drink as boiling kills bacteria and parasites. After researching, I noted that boiling water doesn’t get rid of pollutants. There are plenty of solutions to the issue, for example, the establishment of sediment filters are an inexpensive way to physically trap particles, especially those of a filter size of 1 micron or smaller. (NRDC, 2009) However these filters still do not filter out chemical contaminants. The use of bottled barreled water, though expensive, are generally safe when from a reputable source. Furthermore, Activated carbon filters process most physical contaminants out, such as chlorine, and are EPA approved. Obviously, the key way to target this issue would be to stop it at the core, by removing pollutants from the lakes and river themselves. (WHO, 2011)


To fully assess the risk of drinking Shanghai’s water, we must note that there is a cleaning system to filter the water of the majority of the pollutants. When reading Nick’s post, he noted a water filtering company, Veolia, who first extract their water from underground aquifers and surface water bodies. All the water then passes through a purification process, which includes coarse and fine screening, flocculation and settling, filtration, ozonation and chlorination. (Veolia Water, 2010).These processes can all be explained in further detail in Nick’s blog post. Despite all these processes, nitrates still persist within the water, and hold particular risk to small children, as noted earlier. However, for me and the general population, water pollution holds quite a low risk to our health as it has been filtered numerous times before reaching our taps. The only real risk with Shanghai water is with the concentration of pollutants, not the pollutants themselves. Detrimental health risks only occur in situations in which the concentrations of these pollutants are very high, which is more likely in lesser developed countries, more rural areas, than in Shanghai itself.


References:


About.com (2010). Why is Chlorine Added to Water. Retrieved April 20, 2013 from http://environment.about.com/od/earthtalkcolumns/a/chlorine.htm

Adam Sigler (13 March, 2010). Nitrate/Nitrite Fact Sheet. Retrieved March 19, 2013, from http://waterquality.montana.edu/docs/homeowners/nitrate_fact_sheet.shtml

American Journal of Public Health (2011). Stabilization of Chlorine in Water . Retrieved March 11, 2013, from http://ajph.aphapublications.org/doi/abs/10.2105/AJPH.32.9.1025?prevSearch=chlorine&searchHistoryKey=

NRDC. (2009). Water. Retrieved April 20, 2013, from http://www.nrdc.org/water/

WHO . (January 1, 2011). Nitrate and Nitrite in Drinking Water. Retrieved March 11, 2013, from http://www.who.int/water_sanitation_health/dwq/chemicals/nitratenitrite2ndadd.pdf

WWF Global. (25 October 2010). Threat of Pollution in the Yangtze. Retrieved March 11, 2013, from http://wwf.panda.org/about_our_earth/about_freshwater/freshwater_problems/river_decline/10_rivers_risk/yangtze/yangtze_threats/

One thought on “WAT ER YOU DRINKING? : Tapping into Shanghai’s Water Secrets

  1. After reading India’s post I came to wonder where does our drinking water come from. After all water is a scarce renewable resource, whether it was obtained from the ground, reservoir or lake it must go through some sort of treatment process before it is safe for human consumption.

    This is when I remembered; back when I studied in Hong Kong there was a time period where everyone had a carbon filter water bottle. It was claimed that you could fill it with water from anywhere and it would be safe to drink, as it is filter through the carbon filter. To what extent is a small perhaps 10cm3 block of carbon remove impurities from water and how?

    This led me to wonder what are the different ways of water treatment? After some preliminary research I found several ways in which different types of water are treated including desalination of seawater and the general process of waste treatment.

    In this post I will look specifically at the use of activated carbon.

    Treatment using activated carbon is primarily used to remove large solids through adsorption. In which the contaminants are attracted and held by the activated carbon. (Dvorak, B., 2003). The carbon is a derived form of charcoal and is activated at 1200K where portions of the carbon is oxidized creating many pores within it. (Water Treatment, n.d.). These micro pores can range from 2nm in size to 25nm and it is estimated that in 1lb of granulated active carbon it has the surface area of 125 acres! (Ecologix, n.d.).

    This activated carbon is essentially small crystalline solids of graphite. As we learn in IB Chemistry graphite is an allotrope of carbon, which consists of layers of hexagonal rings of carbon stacked upon one another and held by weak van der waals forces. This can be seen in the following Images:
    Figure 1: Structure of Graphite (Desotec, 2013)
    Figure 2: Electron microscope view of activated carbon. (Desotec, 2013)
    Also as a non-polar compound it is able to attract and bind non-polar organic substances. This explains its effectiveness in removing organic compounds and chemicals. However this means it is unable to adsorb very soluble substances especially those that form hydrogen bonds with water for example nitrates, sodium and phosphates. (HowStuffWorks.com, 2000).

    There are many different factors that affect the carbon’s effectiveness and ability to adsorb the different contaminants. Some key determinants include, surface area of the carbon, the concentration of contaminant present, the solubility of contaminants in water and etc. (Dvorak, B., 2003). Another weakness with using activated carbon as a filter is that over time as the carbon continues to adsorb the contaminant there will come a point of saturation where the carbon is no longer effective. This means that it will need to be readily swapped for a new one or re-activated. (Dvorak, B., 2003).

    So what are the implications of my research? The use of activated carbon is an effective way to remove selective contaminants from the water. However since it is not capable to remove certain for soluble substances such has nitrates it should not be the only method in the treatment of waste water (water from sources near factories, human waste facilities). To further remove these smaller and more soluble contaminants the process of reverse osmosis can be used. This is where pressure is applied on the contaminated water through a semi-permeable membrane, essentially the opposite reaction of osmosis. (Kershner, K., 2008). This process is also used in the desalination of water and other industrial processes. Please refer to the link below for more details:
    http://science.howstuffworks.com/reverse-osmosis.htm
    In the case with filtering tap water or from other surface freshwater sources, one can use an activated carbon filter to obtain safe drinkable water. However one must remember to regularly change the carbon filters. The development of the activated carbon technology has been a key to creating cheap, portable and easy to build filtration system, which can be implemented into key third world nations where clean water is difficult to obtain.

    Dvorak, B., Skipton, S. (2013). Drinking Water Treatment:Activated Carbon Filtration. Publication: Drinking Water Treatment: Activated Carbon Filtration. Retrieved January 23, 2014, from http://www.ianrpubs.unl.edu/pages/publicationD.jsp?publicationId=293

    Water Treatment. (n.d.). Water Treatment. Retrieved January 22, 2014, from http://www.science.uwaterloo.ca/~cchieh/cact/applychem/watertreatment.html

    Kershner, K. (2008, May 8). How Reverse Osmosis Works. HowStuffWorks. Retrieved January 20, 2014, from http://science.howstuffworks.com/reverse-osmosis.htm

    “What is activated charcoal and why is it used in filters?” (2000, April 1). HowStuffWorks.com. Retrieved January 21, 2014, from <http://science.howstuffworks.com/environmental/energy/question209.htm> .

    DESOTEC. (2013). Chemical structure of activated carbon. DESOTEC Activated Carbon. Retrieved January 23, 2014, from http://www.desotec.com/activated-carbon/chemical-structure-of-activated-carbon/

    Ecologix. (n.d.). Activated Carbon. Wastewater Treatment. Retrieved January 23, 2014, from http://www.ecologixsystems.com/product-activated-carbon.php

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