Thursday, April 28, 2011

Checking out the water quality at Singapore's iconic (but mostly forgotten) landmark: Chinese Garden

Some time ago, I was lamenting about the lack of water bodies in Singapore for educational activities. I now realise that I have missed out a wonderful outdoors location for my water quality studies and it is none other than our iconic Chinese Garden. (The nearby Japanese Garden and Jurong Lake Park should also fit the bill as outdoors classrooms though I have yet to check them out.) When I was younger (decades ago?), Chinese Garden was always in the spotlight for shooting of period drama serials by the then SBC (Singapore Broadcasting Corporation) (now Mediacorp). Nowadays, it is mostly forgotten except for a handful of joggers, photographers and tourists. The latest attractions in town are the sexy casino and theme park on Sentosa, as well as the panoramic sky garden and another casino at Marina Bay Sands.Chinese Garden is so "history".

What prompted me to check out Chinese Garden was a friendly meeting with the management of the Garden under JTC (Jurong Town Corporation). They are really supportive of promoting the 2 gardens and 1 park for educational purposes - outdoors lessons, water quality studies, even relevant R&D. Do approach them if you think that they fit your educational curriculum as I am sure they will oblige your request.

Enough chatter. Here are some of the findings on my trip there.

Figure: A rather commonly encountered aesthetic problem is the obvious presence of algae in a few streams and ponds. We didn't try doing any sampling for fear of allergic reactions to algae and their metabolic products.

Figure: Quite a few healthy patches of cattails. We tried sampling for bugs (macroinvertebrates) here as such densely vegetated areas are their favourite haunt.

Figure: A small water body at the dead end of a stream. Because of the lack of flow and circulation, the end of this pond is occasionally overwhelmed by suspended sediments. We also did a sampling of the bugs here.

Figure: Sorting out the bugs from our water sampling. Surprise, surprise... there are healthy populations of various bugs despite the aesthetic problems mentioned above. Lots of shrimps, damselflies, some dragonflies, quite a few mayflies, water bugs, almost no worms and no leeches. The water is biologically (and implicitly chemically and physically) healthier than most water bodies I have sampled in Singapore. Make no mistake, Chinese Garden is THE place to visit for water quality work.

Monday, April 18, 2011

Some random thoughts on floods and water quality

I have been wanting to write something on floods and water quality since our Orchard Road floods make headline news in June 2010. But other committments in life came to the fore and this task became relegated to the background.

Brisbane floods: Up close (18 Jan 2011, ABC News)

Figure 1: This looks like some sort of water treatment or wastewater treatment plant in an industrial area
Figure: Same area as Figure 1 after the flood. Notice that the treatment plant is overwhelmed. If it is a water treatment plant supplying tap water, you can expect contaminants from the flood to go into tap water. If it is a wastewater treatment plant, you can expect untreated or partially treated wastewater to be carried by the flood to who knows where. Depending on the type of wastewater, contaminants can include raw sewage, industrial effluent (heavy metals, solvents etc.) or agricultural waste (animal waste, pesticides, fertilisers etc.).

Orchard Road Floods Straits Times/ Stomp (June 2010)

Figures: The same principle applies here. We had a flood. Flood washed everything around Orchard Road in its path. Let me hazard a guess - "everything" should include motor oil/ fuel (from vehicles), rubbish (glass, paper, aluminium), animal waste (stray animals, rats), pesticides/ fertilisers (lawns, green spaces) and lots of sediment (notice the "kopi susu"-like flood water). Where do you think the flood water eventually end up? Orchard Road is part of the Marina Reservoir watershed so yes, the contaminants end up in our reservoir. Our water treatment plants are supposed to be very effective so most of these stuff should be removed before reaching our taps. Even if this were true, treatment costs will likely rise from an increase in wear and tear of the treatment units handling such a heavy and diverse load of contaminants.

Figure: Tsunami caused by earthquake in Japan (Mar 2011) ( The same can be said of a tsunami. It can carry everything nasty land pollutant in its path far inland, impacting water supplies and wastewater processing. I remember first learning about this term "tsunami" in secondary school geography. It didn't strike a chord with me then. Perhaps there weren't that many tsunamis then. But nowadays, even children know about this term when everyone can see horrific images of death and destruction following its wake. It has also receive much publicity since the tragic Asian tsunami in Dec 2004.

A disaster may be split into 2 phases with respect to its damage. The 1st phase is the disaster itself. Energy from an earthquake or flood causes loss of life and property. This phase usually lasts a short while (though there are floods that take months to recede). The second phase comes in when the population starts to rebuild their lives. The economy is torn to pieces. Food, water and fuel become scarce. Ditto for daily necessities. If law enforcement is weak and the people desperate, social disorder ensues. Without clean water (and food) and proper sanitation, people start coming down with water borne diseases which may spread without check, especially when people are herded into cramped refugee camps. See my earlier post for a fuller discussion on the aftermath of a disaster.

Monday, April 11, 2011

Answering a simple question - what is water quality?

The closest things are usually the ones we miss seeing.

Having blogged for 3 years about water quality, it comes as no surprise (or does it?) that I have not talked more about what water quality is.

Let's try to define it. I am a fan of 1-sentence definitions so I shall do the same here. Water quality simply tells you whether the water is suitable for use. Simple enough? Unfortunately, real life often complicates things. For example, what use? For whom (or what)? What is meant by suitable? How to measure suitable? (There goes the 1-sentence rule...)

What use?
These come to mind - drinking, washing, bathing, cooking, swimming, recreation, industry (food & beverage, wafer fabrication, pharmaceutical, cooling water, boiler water...), agriculture (animals, crops...)... The uses of water seem endless and mind boggling. But it doesn't end here.

For whom (or what)?
Environmental science used to be human centric, focusing only on the applications for society and the effects on the human condition. With the rise of the environmental movement, care and concern for non-human entities are increasingly becoming the norm. (I must stress that humans are too part of the web of life so it makes sense to care for these non-human entities. Anything that goes wrong in the environment will ultimately comes back to impact us. Remember - everything is connected to everything else.)

Have you considered the poor fish living in the wild downstream of your wastewater treatment plant? How about that rare aquatic fern surviving precariously in an increasingly polluted river?

Environmental protection and conservation have now come into the picture. Water quality must be of an adequate standard for organisms (especially aquatic ones) to survive and thrive. As someone pointed out, good water quality is not enough to nourish the ecosystem, you need to adopt a holistic view and protect/conserve the rest of the ecosystem too.

But before we get too carried away, don't forget the mind boggling uses of water listed at the beginning. There are many perspectives to water quality. The key is to first define the use for that water. Drinking water will have rather different requirements compard to industrial and agricultural water. Water quality for human consumption can be quite different from that for a fish or frog.

Just as water quality is only one of the many components of conservation, conservation is too only one component of water quality. You may protest, "what has happened to the 'nature conservation' given in your blog profile?" Nothing has happened. I still believe in conserving nature. But realise that water quality is a big topic, encompassing many different viewpoints that sometimes do not fit in well with one another.

What is meant by suitable? How to measure suitable?
This could be a can of worms so I will try not to open it (at least not in this post). Suitability is described by the various water quality parameters (dissolved oxygen (DO), pH, turbidity, metal content, pesticide concentration and many many more). Obviously, the type of use will determine which parameters are important and the limiting values of those parameters. For example, low DO is not a big issue for human drinking except that the water may taste flat. Yet a low DO water can get a fish killed from asphyxiation. Another example - a zero coliform count is expected of drinking water yet a count of less than 200 per 100mL of water is considered all right for swimming.

"Suitability" can be a dodgy term. Yet, I believe that regardless of the inadequacies of water quality parameters and their limiting values, they at least give us a grasp on the elusive nature of water quality and hopefully allow us to work towards better ways of defining water quality.

Thursday, April 07, 2011

Latest wetland craze - Lorong Halus Wetland

Wetlands seem to be all the rage in Singapore right now. With the launch of Sengkang Floating Wetland in November 2010, we now have the latest wetland launched (kinda reminds me of the incessant condominium launches in Singapore now) at Lorong Halus on top of our old landfill before Pulau Semakau took over. After talking to 2 staff from CUGE (Centre for Urban Greenery and Ecology), I found that there are many more wetlands being built all over our island, being part of experiments to clean up water.

Hey, don't get me wrong, I am all for installing constructed wetlands. If designed and managed well, they are effective in improving water quality (see post on using plants to clean up water). They are also pretty to look at, especially if the wetland attracts a diverse range of wildlife. Unlike artificial concrete and steel in a wastewater treatment plant (WWTP), a constructed wetland is mostly natural which is where its greatest appeal lies. (Though constructed wetlands are supposedly cheaper than conventional WWTP, I was told that our much publicised wetlands run into price tags of six figures or more. Perhaps, most of the cost went into paying the foreign expertise for design and possibly imports e.g. floating mats to make a floating wetland.)

The best thing about Lorong Halus Wetland (LHW) is it is not just a showpiece. It actually works! It functions as a treatment unit for leachate escaping from the former landfill at Lorong Halus. Leachate from a landfill can contain all sorts of nasty contaminants like heavy metals and toxic organics which can escape into the Serangoon Reservoir and subsequently into the water treatment plant.

What does the future hold?
I personally believe that constructed wetlands (a type of phytoremediation - defined as the use of plants to clean up soil and water) will become more widespread in the near future. As society becomes more environmentally conscious (what with the issues of climate change being publicised almost non-stop nowadays), people are starting to look for sustainable and environmentally friendly methods of treating wastewater. Even though constructed wetlands have their limitations (e.g. a need for land), their natural appeal and sustainable character are hard to beat. And if you are business minded, this is one natural technology that should not be overlooked as its market (especially in developing Asia) is set to grow. I will be writing more about this in future posts.

Back to LHW

Figure 1: PUB (Public Utilities Board) seems to releasing this watershed map of Singapore in recent projects. (Read more about how to interpret a similar map in post on Sengkang Floating Wetland.) Of particular highlight is the dark blue (also blown up as a circular insert above) area which delineates the watershed for Serangoon Reservoir.

Figure 2: Compare this old watershed map from PUB to the one in Figure 1. This old map split Singapore into only 3 catchment areas - East, Central, West. I believe this is more for adminstrative purposes (certain PUB departments are also split according to these 3 regions) rather than based on geography.
 Figure: The wetlands are in the upper part of the figure, consisting of reed beds (green with white dots) and polishing ponds (small patches of light blue).
 Figure: As in Sengkang Floating Wetland, there are ample signboards to educate the visitor about the site. Here, it explains why a constructed wetland is needed at Lorong Halus. (Answer: to clean up the leachate escaping from the landfill.)

 Figure: Another signboard explaining the need for polishing ponds after the leachate has gone through the reed beds. (Answer: the ponds are there to remove leftover nutrients and suspended particles.)
 Figure: In the distance, you can see the Serangoon East Dam which closes up Serangoon Reservoir. I imagine like most local dams, it only allows water to flow out and not in from the sea, hence, keeping the reservoir water fresh and preventing seawater from intruding.
 Figure: One of the reed beds consisting of Papyrus. You probably find that this layout does not fit the definition of a wetland but it does or at least, it is defined as a constructed wetland. This type is known as HSSF (horizontal sub-surface flow) where the wastewater flows in the sub-surface via the plant roots where treatment takes place.
 Figure: Another reed bed, notice the gravel filling up the constructed wetland. This is advantageous because the wetland is "covered up", hence is aesthetically more acceptable - no unsightly wastewater and little offensive odours. Hey, you can even walk across the gravel bed as the gravel filling is well packed. Also the use of gravel allows the wastewater to flow underground easily through the empty spaces among gravel pieces.
Figure: A polishing pond. This design is also known as FWS (free water surface) as opposed to HSSF. By this time of the treatement process, the wastewater should be more or less cleaned since the reed beds have already done their dirty job of removing most contaminants. Therefore, an open water surface (or FWS) will be quite reasonable here.

(Update: you can find out more about how to clean up rainwater before it flows into our reservoirs in PUB's ABC (active, beautiful & clean) waters design guidelines. These guidelines advise developers and industry professionals to incorporate environment friendly features such as rain gardens, bioretention swales and wetlands in their developments.

Remember our watershed concept? Almost 70% of rainfall in Singapore lands in a watershed somewhere, ultimately ending up in our reservoirs. The plants and soil media employed in the above features act as “filters” to remove nutrients and sediments from the water going into our waterways.)