How to reduce flooding in Singapore? Harvest more rainwater!

Harvesting of rainwater may sound foreign to most of us even though this term is commonly used in other countries. It simply means collection and storage of rainwater. It may be on an individual, residential, community or even national basis.

Actually, Singapore has been harvesting rainwater for a long time on a national basis. From PUB's webpage, two-thirds of the land area here is available for rainwater catchment (Yes, right, "catchment" is more commonly used here).

(Figure: www.pub.gov.sg/water/Pages/LocalCatchment.aspx)

Is so much of our area covered by reservoirs? NO! It means that land (residential, industrial, recreational, waste etc.) is used to funnel all that rainwater into reservoirs. For example, rainwater falls on rooftops, flows into drains which lead into canals, ultimately joining up with a reservoir. Because of the flash floods in June, everyone now knows that Orchard Road is part of the catchment area for the Marina Reservoir. Talk about practical environmental education.

Indeed a very clever system to alleviate the shortage of water in this densely populated island. However, it suffers from a few drawbacks.

One, in times of heavy rainfall, no way will the reservoirs be able to hold so much water. The natural thing to do is to drain the excess into the sea. (E.g. the Marina Barrage is well touted to be able to do this in the event of heavy rains.) This of course means a waste of fresh water. AND IF the excess CANNOT be drained (e.g. blockage of some water way), flooding will result. In the (good?) old days when Singapore is still a tropical jungle, most rainwater will be soaked up by the vegetation and soil. But with the increase of built-up area, we no longer have such a luxury. Most rainwater will flow over the ground surface straight into drains and canals or perhaps accumulate in some low lying area as a flood.

Another challenge of open reservoirs like ours is the loss of water through evaporation. In the dry months, the water level in the reservoirs drops not only because of the lack of rainfall but also through the above mentioned loss.

This article predicts that the rainwater harvesting (RWH) markets in Europe and India are set to experience high growth rates in the coming years due to a rising fresh water shortage. More RWH systems will be installed at the residential, commercial and industrial levels.

Guess what? This is nothing new in Singapore! Changi Airport has such a system. Nanyang Polytechnic has one too. The airport is reported to satisfy one-third of its water demands in this manner, saving $390 000 per year. Such water is normally collected on the roof-top and undergoes minimal treatment for non-portable use e.g. toilet flushing, firefighting drills, watering of plants.

Imagine... if we have more of such systems, not only will our reservoirs be less stressed in times of heavy rain, there will also be less loss of precious fresh water through evaporation.

If your interest has been piqued, how do you set up a RWH system. SIF Technologies is selling a "chemical free RWH system". Chemicals are sometimes added in conventional water storage to discourage microbial growth. (Chlorine in PUB water does this job.) In the case of SIF, they are using a proprietary non-chemical means to do the same thing.

But RWH can be simple and cheap. Consider this 3rd world method of RWH. However, remember to always discard the first 10min of so of rainwater as it may contain pollutants from the air or your roof-top.

Figure: using a tin roof to collect rainwater (Water for Life, Hesperian Foundation)

Figure: My own version of a RWH system for use in a high-rise flat from a project several years back. (Naturally, we can't have every household in a HDB block harvesting rainwater. I suspect only the top floors will get any significant amount. The other concern is not to have a high-rise RWH system becoming killer litter.)

Oh, before you rush out to install a RWH system, here is an extract from Singapore Law.

SEWERAGE AND DRAINAGE ACT

PART V PROTECTION OF WATER RESOURCES
Prohibition on extraction of water
No person shall, without the approval of the Board (PUB), construct any works for taking or intercepting water from any place or sea, within the territorial limits of Singapore.

However, I believe the law has been relaxed for residential installation provided the storage tank is less than a size of 5x2x2m. Anyting bigger will require a water-borne fee to be paid. But if you are planning a system for your company or school, you still have to go through the bureaucracy for permission. One last point, check out the guidelines for collection of rainwater at NEA.

(Update: Rainwater Harvesting Seen as Solution for Drought and Flood Control: In Kenyan cities like Nairobi, rainwater harvesting is seen as a solution to multiple problems.)

Water resources from Loughborough University

Loughborough University's Water, Engineering and Development Centre (WEDC) has a new knowledge base where 150 books, over 1700 conference papers and hundreds of other knowledge outputs are available for download FOC if you register.

Topics range from water supply, sanitation, emergencies/disasters, lessons from floods and many more.

http://wedc.lboro.ac.uk/knowledge/know.html

Revisiting Pasir Ris

Thanks to Ria for her post on Pasir Ris water quality deteriorating due to the high concentration of enterococcus bacteria in the water.

An explanation of the situation from NEA press release (7 Sep 2010)
"According to results from a study released by NEA in 2009 during the last annual assessment of water quality at beaches, Pasir Ris beach’s water quality is affected by various possible sources, including minor leakage from older sewers, moored vessels, animals, as well as discharges from small-scale Sewage Treatment Plants (STPs) that presently serve the more remote areas in Pasir Ris. The low water currents in the concave part of Pasir Ris beach are not effective in diluting and dispersing the discharges."

I do not have the answers to most of the whys and hows in this issue. Instead, I will pose a few more questions. (Does this complicate the issue further?)

Fish farms in the vicinity

1. I believe the staff on these farms dispose of their bodily waste directly into the sea straight without treatment so yes, this can be a source of the E. bacterium. (Anyone care to refute the part on direct disposal?)
2. Fish waste is another issue altogether. Yes, they may decompose and cause the dissolved oxygen level to plummet but enterococcus??? Not likely as the bacteria normally comes from humans.

Aging sewage treatment plants (STP) in Changi and Tampines

1. Can anyone throw some light on these plants? Where are they? Industrial (probably)? What kind of industry? What is in the sewage - human, animal or industrial waste?
2. Doesn't sewage go into the PUB sewers?
3. Why are they allowed to discharge unhealthy effluent into our waterways? Any discharge into a watercourse must be approved by NEA under the trade effluent regulations of Environmental Protection and Management Act.
   
   Unfortunately, under the same regulations, there is no mention on the limit of coliform, enterococcus or even bacteria for a discharge.
   
   The closest will be BOD5 (biochemical oxygen demand for 5 days) under the regulations. (In simple terms, BOD5 is a measure of the biodegradable substances e.g. faeces, urine, food in the water.)
   
   "The 5-day Biochemical Oxygen Demand at 20° Celsius (referred to in this paragraph as BOD) and the Chemical Oxygen Demand (referred to in this paragraph as COD) of any trade effluent analysed in accordance with regulation 11 shall not be in proportions greater than those set out below:
   (a) 50 milligrams per litre of BOD and 100 milligrams per litre of COD where the trade effluent is discharged into a watercourse other than a controlled watercourse"
   I assume the waterways which lead to the sea off Pasir Ris are non-controlled watercourse since they do not go into a reservoir. Still, 50mg/L of BOD5 is easily exceeded by normal domestic sewage (100 - 300mg/L). (Agricultural or food wastewater may go into the thousands in terms of BOD5.)
   
   How efficient are these STP in treating sewage i.e. percent reduction in BOD5? Did anyone check whether their discharges exceed the limits set out in the trade effluent regulations?
   
   Nevertheless, it is entirely possible that the discharge can pass the BOD5 test but yet contains enough human waste to give a high enterococcus count in the sea.

Sembawang Park

The water quality off Sembawang Park (also given in the same report) seems fine. Being located along the Johor Straits as is Pasir Ris Park, I imagine the seawater dispersion there is as dismal. Perhaps, the smaller number of fish farms and the lack of aging STPs and leaking sewers do make a difference.

Introducing the British Berkefeld filter - something you can count on when the chips are down

The latest earthquake in New Zealand (Christchurch and surrounding area, 4 Sep 2010, 4:35a.m. Saturday, 7.1 magnitude) got me thinking about the supply of water again but this time round it prompted me to pen it down. (Long post as follows)

If you have been following this year's (2010) natural disasters - earthquakes in Haiti, Chile; flood in Pakistan, public water supply has always been a fragile creature. Infrastructure can be destroyed, piping and storage tanks can be broken.

In Pakistan, the deluge caused natural sources of water (e.g. wells, springs, streams) to be contaminated with whatever the flood water carried - human and animal waste, pathogens from corpses and carcasses, pesticides from farms, heavy metals from industry. In the short term though, it was the water borne diseases that caused the most problems - diarrhea, dysentry, cholera, typhoid etc. The breakdown of sanitation and water supply led to a nightmare for public health (probably nowhere near top notch even before the flood).

Bottled water naturally became a valuable commoditity as seen in Chile when it became one of the top looted items (together with bread and candles). I imagine the same would have occurred in Haiti if there was enough bottled water to go around to be looted.

Being a developed country, New Zealand was spared from serious looting (some still took place according to the news) or outbreaks of water borne diseases. Heck, no one was killed by the quake as according to some experts, the strict building codes to quake-proof its structures have helped. (Compare against 230 000 killed in the Haiti quake.) Nevertheless, the sewage pipes were broken in the quake, allowing sewage to mix into the drinking water supply which probably probably suffered from broken piping too.

Consequently, residents in affected areas were asked to boil their tap water for drinking. I am thinking: these people are lucky (despite the quake and all). They still have electricity or/and gas. Imagine... if you have no gas, no electricity and only sewage infused tap water, how are you going to boil your water?

Imagine some more.... the NZ scenario (without the gas and electricity) happens right here in good old SG (assuming we survive the quake), do you have a wood burning stove and charcoal at home? How about a camp stove with extra gas tanks? The lucky ones will be those NOT using piped gas. The years of effort to heft around those gas cylinders would have been worth it.

Do you have Aquatabs on hand? Bleach? Do you know how much to add into water? Personally, these are not my favourite choices because of strong chlorine taste and many health controversies of overchlorination. By the way, if you opt for bleach, only use the straight ones without extra ingredients e.g. scent.

Boiling is good if you can do it but it only removes the bugs and not all the other nasty stuff (pesticides, metals) in the water. Imagine having a Pakistani scenario here. I will boil my water before running it through a good filter.

I personally recommend the British Berkefeld (or Doulton) gravity filter. (In America, it is sold under the name of Berkey.) No water pressure, no electricity needed. Simply pour your water through the top and collect clean water at the bottom. The key element in the setup is the filter candle with the ATC SuperSterasyl being the best. It has a ceramic outer shell impregnated with silver. The ceramic physically remove microbes and particulate matter from the water while the silver suppresses bacterial growth. The water next enters a granular activated carbon core containing a metal ion removal medium (works by ion exchange, I believe) to eliminate many organic compounds (e.g. pesticides), chlorine and metals (e.g. lead, cadmium).

Figure: The external setup of the British Berkefeld stainless steel gravity filter minus the faucet which should be attached near the bottom. It is certainly not small (this is already the smallest stainless steel model) so it should be used for the family or small group at a static location.

Figure: Opening the lid reveals 3 holes for fixing a filter candle each

Figure: The heart of the filter system - ATC SuperSterasyl filter candle. Notice the white ceramic exterior. Water enters through the ceramic and filtered water leaves through the black nozzle on the right.

Figure: The top portion is removable for fixing the filter candles. Filtered water goes into the bottom portion for dispensing via a faucet.

Having one of these filters will certainly add a great degree of water security to any family. And if you are involved in overseas community projects, keeping one with you serves as insurance, especially if you are not sure of the water quality or source of your drinking water.

This line of filters may be procured locally from Arkwater. Of course, I am in no way affiliated with the company except for purchasing these filters from them.

Sembcorp water technology prize (Sec 2 - JC2)

Just saw the poster below even though my colleagues have mentioned to me that they are involved in the competition. More details are found on PUB's webpage here. If you are considering to participate, the deadline is 18 Sep 2010.

Apparently, there is this push into membrane technology as the solution to getting clean water. Membrane technology is certainly cheaper and more energy efficient compared to traditional distillation. Theoretically, it can remove almost any impurity (salt, organic compound) in water. A membrane is basically a filter with very tiny pores. Depending on the specifications, some are small enough to block off microbes while others can block off even dissolved ions like sodium and chloride, allowing only water molecules to pass through. Seawater and heavily contaminated water can be made into potable water.

Naturally, pushing water through such tiny pores requires lots of pressure (and energy) so using membrane to purify water (e.g. reverse osmosis) is by no means cheap but prices seem to be dropping all the time.

Other challenges. Membrane fouling is a major problem. After some time, contaminants accumlate on the surface of the membrane till it can no longer function efficiently. It is time to either clean the membrane or replace it entirely. To prolong the operating life of a membrane, it is essential to have good pretreatment. In other words, you need to have many steps before the actual membrane itself to filter off increasingly smaller contaminants. Imagine having several filters of decreasing mesh size so that the final filter will not be stressed by a big load of contaminants.

Of course, this sort of setup comes with controls and maintenance operated by skilled personnel. Though there are now remote control interfaces, allowing a treatment unit in say, Africa to be controlled by a technician in America, you still need boots on the ground to attend to certain maintenance tasks. Therefore, this technology is still not so useful for rural areas without the presence of skilled personnel. Very often, even with skilled personnel present, the local population may not be able to operate the treatment unit once these personnel leave.

But for Singapore, sure, no problem. Membrane technology is the way to go!

A quick update for the past months

I would like to convince myself (and you) that my packed work schedule has prevented me from posting anything since the end of May. I know it is a shame but I am also sure that inertia has played a large part - not having posted for so long propagates the said behaviour :-)

In part to prove that I am really "busy" and to update you on the past activities, here is a summary of my "work".

June - July
Conducted "Freshwater quality and biodiversity" course for Crescent Girls, Henderson Sec Sch, Clementi Woods SS, Queensway SS. It was back to a tributary (sort of a naturalised drain) of Sg Ulu Pandan for more water quality testing and bug hunting.

Figure: The group hunt (for bugs)

Figure: Don't forget the water quality parameters

Figure: Sorting out the spoils of the hunt

Figure: A rare find - freshwater eel - too small for unagi though

Figure: The common Dragonfly nymphs though perhaps not so commonly seen by the students

Conducted a round of 6-day intensive AEM (advanced elective module) "Water quality and pollution".

Figure: On first sight, nothing wrong with the scene. But if you look closely enough, lots of people are looking down on their pants and shoes. This is what happens when you venture out in the wilderness in the rain and through knee high vegetation. All manner of creepy-crawlies are out their homes, latching on to the hapless passer-by (i.e. us).

Figure: Part of Ngee Ann Stream. Looks like another canal except that this used to be a natural stream with thick secondary forest on both edges. See next figure.

Figure: The same part of Ngee Ann Stream as the figure above but a year back. Note the vegetation stretching right to the edge of the secondary forest stream

Figure: An unusual find - a catfish struggling against the current in the "canalised" Ngee Ann Stream. Why was it doing so? I have no idea. Perhaps it should have just flowed along with the tide of change as what the rest of the stream did when it gave way to "development".

Figure: Due to the earlier heavy rain (what else is new in Singapore?), the whole canal was flooded, preventing the students from sampling the water (too dangerous).

Figure: The same part of the canal as the figure above but in drier times and more than a year back.

Figure: I simply can't resist putting in this routine group photo. Must show that the participants are in good spirits, right?

Singapore International Water Festival (27 Jun 2010)

Once again, I was roped in to organise the event "Amazing Greenviron Challenge" - an environmental quiz of sorts with indoor and outdoor components at the Marina Barrage. Weather was terrible in the morning so the outdoor part has to be moved indoors. (Right, rain was indeed heavy in June, giving rise to the shocking floods in downtown Singapore.)

Figure: Only 1 photo to show you here - the super group photo with organisers, student helpers and participants.

(Are we not done with the summary yet??? Afraid not... Did I mention that I had a tight schedule then?)

Water Quality Monitoring (WQM) (19 Jun 2010)

Amidst the tight schedule, I managed to sneak in a round of WQM with Team Seagrass at Chek Jawa.

Figure: On this rare sunny June morning, my students prepared their equipment for WQM.

To top it off, I attended the 4-day Wilderness Medical First Responder (WMFR) Course by OBS (Outward Bound Singapore) on Pulau Ubin. More on this in a later post.

Figure: WMFR participants and our dummies

WQM at Pasir Ris

Ah yes, the problematic kid on the block with regards to water quality - Pasir Ris Beach. (The latest advisory on its "fair" water quality is found here.) We checked out this notorious locale on this rainy July morning. Perhaps unknown to most people, this stretch of sand hosts 2 significant patches of seagrasses even though they are not monitored by Team Seagrass. (Some of the Team's members do however check out the seagrasses here in their own capacity.) And since there are seagrasses here, my team will of course be interested in the WQ.

Figure: 1 patch of seagrasses near Sg Loyang

Figure: The 2nd patch of seagrasses near Sg Tampines. I was told that there is a smaller patch further west near the end of Pasir Ris Park. We did not check this one out though.