Background
This report has been developed as a response to a Call For Proposals (CFP) to developing solutions for engineering problems.
According to World Health Organisation(WHO, 2019), safe and readily available water has always been one of the key goals globally. The article stated that the ‘United Nation(UN) General Assembly explicitly recognized the human right to water and sanitation’. This shows a huge emphasis had been placed on water quality. The consumption of water in Singapore is approximated 430 million gallons of water per day (The Straits Times, 2018). In the same article, it was stated that there are four sources of water supply in Singapore: local catchment water, imported water, NEWater and desalinated water; they each can only provide up to 10%, 60%, 30%, 25% of the water needs of the entire island country respectively.
Singapore provides one of the highest quality of municipal water supply in its surrounding region. The quality of water is kept within the World Health Organization (WHO) drinking water guidelines and US Environmental Public Health (Quality of Piped Drinking Water) Regulations 2008 (Refer to Figure 1). According to Singapore’s water agency Public Utilities Board (PUB, 2018), the quality of supplied water is assured through routine chemical and bacteriological water samples collected daily across the island. PUB also monitors the water quality at every stage of their service reservoirs and water treatment plants through online-sensors before dissemination to the public.
Despite these efforts to ensure a stable supply of clean water, PUB (2018) has stated that water from the taps can sometimes still appear brownish. They stated that this is due to unforeseen circumstances such as pipe leakages or flushing of fire hydrants, where the resulting change of direction or rate of flowing water can cause the resuspension of excess iron, manganese and other dissolved metal deposits that have accumulated over time inside the underground municipal water pipelines. Consumption of water that contain excess iron and manganese could leave a negative impact in aspects of neurological as well as physically. According to Passaic Bergen Water Softening (2017), water with excessive amounts of dissolved minerals such as iron and magnesium can have negative effects on your skin. Water with iron doesn’t blend well with soap. This, in turn, can lead to skin problems such as acne or eczema. At the same time, T&H Blog (2015) states that long term exposure to high concentrations of manganese in drinking water is associated with toxicity to the nervous system, producing a syndrome called Manganism.
According to Xue (2014), there was an example case where thousands of households in the Punggol estate were affected by discoloured tap water. It was caused by the mineral sediments in a water pipeline being stirred up during valve operations on a potable water pipe along Tampines Expressway. The contaminated water in the mains were only resolved by the next morning after PUB and Pasir Ris-Punggol Town Council subsequently flushed the affected water tanks, although the problem has been solved but the residents were still advised to run their taps until the water is clean. This leads to wastage of water and also inconvenient for the residents.
Moreover, the routine tests that PUB conduct are only indicative of the water quality in the PUB pipes upstream. There is currently no way building owners/facility managers(FMs) can be aware of any change in quality of water once it enters their premises. Therefore, the users in household will be the first to find out the discolouration instead of the FMs. This will eventually lead to disputes between the household users and FMs, which are supposed to be prevented in the first place.
1.1 Current Situation
In Singapore, when potable water is supplied to a private building, it is done through a ferrule connection that splits off from the main underground municipal water pipe. The water is then drawn towards the building through the use of a pump, before the pipe leads into a water tank. This water tank then stores and distributes water in a network of smaller service pipes directly to a user’s taps when it is opened. The capacity of the water tank is usually built with at least 24 hours of usage volume as reserve water supply if water supply is ever disrupted. (Refer to Figure 2.)
In the event of discoloured water, once water exiting the taps have become brownish, it would indicate that the brownish water has already entered the water tank and diffused throughout the entire water supply system in the building. The entire capacity of the tank (~24 hours of reserve supply) is rendered unusable.
The contaminated water would go undetected for a while as more and more brownish water flows into the distribution system. It might be too late when the discolouration reveals itself— when canteen cooks have already used it for cooking and hundreds of students have consumed them. The sudden drop in water quality would also overload and choke the filters inside of water coolers and dispensers.
Currently, the only process to remove the polluted water involves the halting of water supply, then flushing of contents inside the entire water tank is only completed with the refilling of fresh water— with all the water ticking through the tariff meter. Apart from the wastage of water, it would be expensive for facility managers to deal with the aftermath should brownish water ever enter their water tanks.
There should be preventive/corrective measures implemented so that facility managers can effectively handle influx of such unpredictable brownish water from reaching the end-users.
1.2 Problem Statement
In the upcoming Singapore Institute of Technology @ Punggol campus, potable water supplied should always be within World Health Organisation (WHO) clean drinking standards at all times.
However, due to the absence of current measures, the FM of SIT has no way to know should any fluctuations in water quality occur, and thus have no way to be prepared to deal with them in time.
1.3 Purpose Statement
The purpose of this report is to propose to SIT to install a pre-emptive measure in the downstream potable water supply service pipeline as an early buffer to control and prevent potential contamination of the water tanks in SIT@ Punggol.
Proposed Solutions
The team highlights two solutions to manage the potential influx of discoloured water into their water supply distribution system.
2.1 Installing active water sensors (Solution 1)
The current water system in most buildings are unimpeded pipelines that directly link to the building’s water tanks. Due to the absence of existing measures, should there be any dip in water quality, the discoloured water will directly flow into the water tank, rendering the entire water supply unusable.
The team proposes the installation of an active water sensor directly onto the main water pipe prior to the pump. This allows early detection in the case of a supply influx of lower quality water before they even reach the pumps. With the ability to instantaneously detect these fluctuations, the pump can be set to automatically withhold its operation. A solenoid-controlled pilot valve downstream can then be programmed to shut off so that the brownish water do not travel any farther. This prevents dirty water from ever reaching the water tanks. It would nullify the need to wash and flush the water tanks, saving time and reducing the wastage of water in the occurrence of the inevitable influx of discoloured water.
2.2 Installing modified water treatment system in water tanks
Centers for Disease Control and Prevention (CDC, 2009) states that water contamination can occur even in the safest tap water supply. The article also states that one of the causes of contamination could be the ‘improperly maintained’ pipeworks. The idea of installing water purifier/treatment system in water tanks is to ensure that water quality is maintained clean when it is being drawn out from water tank. It would either be: set on constant operation, re-treating the water in the water tank at all times; or set to be activated for treatment upon the influx of brownish water from external factors like pipe leakage. It can also act as a failsafe to the first solution. Implementing this on the internal water system would allow the water supply quality to be independently controlled by the facility management instead of being completely susceptible to external sources of contamination. In the event of external contamination of water supply, water treatment system can be in place to purify the water/keep the contamination to the bare minimum. Some of the common methods of water treatment system includes filtration, disinfection, distillation, water purifiers or a combination of the mentioned methods. The water treatment system should include the following to restore initial water quality parameters:
2.2.1 Active carbon / Adsorption
Active carbon is a method of filtration that involves passing water through an active material that removes impurities chemically as they pass through (Chris,2019). The author states that charcoal has a large internal surface area that helps to draw and ‘trap chemical impurities through a process called adsorption’. This process helps to remove non-polar substances, odor and taste of the water.
2.2.2 Ozone water purifiers
According to brighthubengineering.com, ozone water purifiers are a smaller version of those used in municipalities. Ozone water purifiers are located at the water intake point between the tank and the intake to ensure the water supply are disinfected before entering the water tank. Ozone water purifiers work by oxidizing most bacteria and bonds with many dissolved materials that result in them precipitate to the bottom of the water. Ozone water purifiers is effective in removing iron and manganese as well as freeing chlorine to kill even more microbes if used in a multiple step systems.
Benefits of proposed solutions
Among the two solutions proposed, we have also done research to find out its benefits.
3.1 Active water sensor
To preserve the water quality, it is important to monitor the water parameters. The use of wireless sensor enables a more accurate map of water status and allows permanent deployment of monitoring in location that has difficulty in accessing without the need of FMs manually retrieving the data. Wireless Sensor Networks (WSNs) is small and inexpensive devices with sensing, processing and transmitting the data to the FMs on the water quality. The sensor will provide real-time data to FMs, if the sensor detects that there is some problem with the water quality, it will alert the FMs to investigate the water and resolved the problem as soon as they can.
3.2 Water treatment system
Water treatment system is a combination of different components that complement each other to achieve the optimal result. Water treatment system helps to recreate the water quality of the initial phase after the water is treated by removing most of the impurities in the scope of micro-organism. Water is separated from unwanted substance once it has been purified. Water treatment system does not require too much humans intervene as to control how it works. Water treatment systems are able to obtain the main objective of keeping the water quality to be within the drinking standard of WHO/prevent people from drinking contaminated water.
Drawbacks of proposed solutions
We also identified possible drawbacks of the two proposed solutions for your consideration.
4.1 Active water sensor
A sole electrical sensor acting as a preventive measure to ensure a constantly-clean water supply means that its reliability is a huge concern. There would be a need for regular maintenance for the sensor; it might relate to increased cost for the FM of SIT@Punggol if 3rd party contractors were to be hired for regular maintenance on an ad-hoc basic
A guarantee-contract with the sensor manufacturer for regular scheduled maintenance would be recommended, as long-term contracts tend to be cheaper in the long run.
4.2 Water treatment system
Water treatment system requires all components to be in working condition. In event of spoilt/damaged components, water treatment system would not be as effective in acquiring its objective of purifying water. A considerable amount of energy consumption would be required to allow water treatment system to run at all times as a preventive measure against contaminated water. Constant check schedule has to be made to identify if the water treatment system is working. The drawbacks of water treatment system can result in a worse water quality if maintenance is not done consistently. Hence, daily maintenance is required for water treatment system to work efficiently and effectively. Water treatment system might be considered an ‘overkill’ as a preventive measure contamination in water due to leakage in pipes since the water supply has already been treated before.
Evaluation
Our team made benefits and drawbacks to two of the solutions and we analyse that implementing active water sensor is the best way(cost effective/reliable/credible) to solve our issues.
5.1 Prevention over correction
Firstly, active water sensor is able to detect any kind of impurities when there is fluctuation in the pipes. However, according to Madans (2018), ozone water purifier can only treat water to a certain degree like iron and manganese, but it does not remove chlorides, sulfates etc. To add on, water treatment system can treat the discoloration but there are other impurities still remains that are not visible to naked eyes. Whereas, active water sensor is able to detect any impurities, although it cannot treat water.
5.2 Cost
Secondly, active water sensor cost cheaper compared to water treatment system based on maintenance cost. As mentioned above, the benefits for water treatment system, it has a combination of different components. Therefore, the cost for maintenance of water treatment system is relatively higher compared to active water sensor.
To conclude our evaluation, we decided that active water sensor should be implemented in SIT at Punggol because it is more reliable and cost effective. Another optional suggestion by us is to implement both solutions as a bundle in SIT Punggol.
Methodology
This section details the methods used by the team to gather information for the report.
6.1 Primary research
The team has one member who had worked as an assistant engineer in PUB in the past. During his 2-year tenure, he had some exposure to the water distribution network systems in many different types of buildings. He also had the opportunity of witnessing the rectifications works that resolved a discolouration event similar to the subject of this report. We used this experience as source information for the current situation in the background.
A phone-call interview was also done with a senior assistant engineer in PUB, Mr Mohd Sazali Bin Tarsim. With 42 years of working with water services, he was able to provide insight on some of the background and the current existing practices of managing occurrences of discoloured water— from both the municipal side as the water supply and the facility management as the receiving end.
A survey was then conducted to gauge how much importance students of SIT@Dover place in the supply of clean water, the views on Singapore’s current water supply quality and how they would react if discoloured water were to flow from the taps in campus.
6.2 Secondary research
The team did research through the internet and was able to obtain online information, statistics and standards published by government websites and research journal articles for the background information and other relevant information.
Conclusion
Despite Singapore boasting a clean supply of water, the occurrence of discoloured water can still happen on the downstream. The rectification thereafter would not only be costly but also interrupt campus operation due to the halting of water supply. It may also give rise to difficult situations such as angry tenants in the canteen and students getting sick because of the late detection arising from the absence of safeguard measures.
Implementation of the proposed solutions would allow the water supply in campus to operate undisrupted in the occurrence of any discolouration. It would ensure utmost quality of water supplied to students and tenants at SIT@Punggol, leaving them clean and healthy.
References
