Monday, January 31, 2011

The things that nobody told you about Pasir Ris

The water quality off Pasir Ris Park has piqued my interest since it has been in the limelight for failing the Enterococcus test for primary contact activities (e.g. swimming) for 3 years in a row (2008 - 2010) and the mass fish kill in Dec 09/ Jan 10 (see previous posts). I also found out that further back in Dec 06/ Jan 07 (1, 2, 3), another mass die-off has been observed and the reason was suggested to be a sharp drop in salinity (Update: In her blog, Ria Tan questioned whether Chek Jawa will survive the incessant rain in Jan 2011). Therefore in 2010, I decided to get my team to test out the water quality off Pasir Ris at 2 patches of seagrasses - 1 close to Sg Loyang and the other close to Sg Tampines.

Figure: Patch of seagrass near Sg Loyang

Figure: Another patch of seagrasses near Sg Tampines

Fast forward to the present, and we have some interesting results to share, not just on Pasir Ris but also on the other 2 locations we monitored. Evidently, Enterococcus is not the only thing we have to worry about.

Data were obtained from sampling seawater and sediments in three selected seagrass areas, namely Chek Jawa (CJ), Pasir Ris (PR) Park and Pulau Semakau (PS) from June to December 2010. Sampling dates and times corresponded to tide levels of 0 to 0.5m for safety reasons and ease of seagrass observation. Our team made 6 visits to Chek Jawa (2 sites), 6 visits to Pasir Ris Park (2 sites) and 2 visits to Pulau Semakau (3 sites) during the monitoring period. (The smaller number of trips to Pulau Semakau was due to logistical constraints hence the team could only head there together with Team Seagrass on their routine seagrass monitoring sessions.)

Our on-site tests include air temperature, water temperature, pH, dissolved oxygen (DO), electrical conductivity (EC), turbidity and nutrients in water - ammonia (NH3), nitrate (NO3-) and phosphate (PO43-). Laboratory testing of water samples involves Escherichia coli (E. coli), chemical oxygen demand (COD), total alkalinity, total hardness, calcium and magnesium hardness, metal ions (aluminium, copper, iron and lead) and chlorophyll a. Sediment samples were also brought back to the laboratory to analyse for nutrient content - ammonia (NH3), nitrate (NO3-) and phosphate (PO43-).

Summary of results

The values below were obtained by averaging all the results for each location. For ease of reading, only the notable water quality parameters are highlighted.

* ND = not detected

DO (mg/L) 10.5 (CJ), 8.79 (PS), 5.85 (PR)
DO is significantly lower at Pasir Ris. While considered acceptable compared to waters elsewhere in Singapore, these DO levels were relatively low for a seagrass area which is supposed to photosynthesise and produce oxygen in the day.

EC (mS/cm) 43.9 (CJ), 46.0 (PS), 42.7 (PR)
The average EC appeared consistently healthy for all 3 areas except for Chek Jawa in November 2010 for which the EC plummeted to 24.67 mS/cm at site 2.

Turbidity (NTU) 30.6 (CJ), 18.9 (PS), 262 (PR)
The water at Pasir Ris is significantly more turbid. Turbidity measures the loss in transparency in water due to the presence of suspended particles such as phytoplankton and silt. Fishes start to experience stress when exposed to a turbidity of 10-100 NTU for several hours.

E. coli (CFU/ml) 17.3 (CJ), 2.17 (PS), 23.4 (PR)
Though E. coli is a different bacterium from Enteroccus, it too indicates the presence of faecal contamination, just like Enteroccus.

Pasir Ris and Chek Jawa are significantly higher in E. coli count compared to Pulau Semakau.

E. coli has the highest count at 76 CFU (colony forming unit)/mL in November for Pasir Ris site 2. United States Environmental Protection Agency (USEPA) standards provide a maximum of 10 CFU/mL faecal coliforms for primary contact activities e.g. swimming, and a maximum of 50 CFU/mL for secondary contact activities e.g. boating.

COD (mg/L) 135 (CJ), 136 (PS), 132 (PR)
Surprisingly, the organic matter content in all 3 areas was rather similar and compares well with values obtained in our coastal areas in 2009.

Iron (mg/L) 0.998 (CJ), 0.314 (PS), 1.34 (PR)
Though not considered a threat to marine life, Pasir Ris has the highest iron concentration.

Aluminium (mg/L) 0.612 (CJ), 0.0148 (PS), 1.64 (PR)
Pasir Ris has significantly higher concentration of aluminium. The toxicity of aluminium depends to a large extent on the water pH, with the most toxic aluminium compound forming at pH 5.2-5.8. At pH 7.0, a concentration as low as 0.52 mg/L was found to reduce the growth of rainbow trout. In another example, a mass kill of maraena and peled fry occurred at 0.3 mg/L at a pH of 7.0-7.5. Seawater contains an average of 0.01 mg/L aluminium.

Lead (mg/L) 0.181 (CJ), 0.0428 (PS), ND* (PR)
Superb! Pasir Ris water has no lead detected!

Chlorophyll a (µg/L) No data (CJ), No data (PS), 7.59 (PR)
Though not shown in the averaged result above, chlorophyll a concentrations peaked at 25.1 µg/L at site 2 and 19.2 µg/L at site 1 for Pasir Ris in December. This placed the water within eutrophic condition as given under the guidelines for USA (10-500 µg/L). Eutrophic water has excessive nutrients which support an abundance of algae releasing chlorophyll a.

Nutrient in Water

Ammonia (mg/L-N) 0.174 (CJ), 0.178 (PS), 0.345 (PR)
Pasir Ris has significantly higher concentration of ammonia. Ammonia is toxic by itself. It can also contribute to eutrophication.

Nitrate (mg/L-N) 0.103 (CJ), 0.0875 (PS), 0.242 (PR)
Pasir Ris has significantly higher concentration of nitrate. Nitrate can contribute to eutrophication. Concentrations of 0.1-0.75 mg/L nitrate + ammonia N in fresh waters or even less in saline waters have been enough for a bloom.

Phosphate (mg/L-P) ND* (CJ), ND* (PS), 0.103 (PR)
Pasir Ris has significantly higher concentration of phosphate-phosphorus. Like nitrogen, phosphorus can contribute to eutrophication. A level of 0.005-0.5 mg/L P is already enough to cause phytoplankton blooms.

Friday, January 14, 2011

I have tonnes of water at my door but none in my pantry - Queensland floods

If you have been reading into floods, earthquakes and other disasters, you should have guessed that the scene portrayed in the following figure is "normal". In fact, this photo immediately caught my attention, prompting me to write this post.

100,000 to lose power, supermarkets bare as flooding crisis continues (11 Jan 2011)

Figure: Actually, the amazing thing about this scene is there ARE still bottles of water on the shelf. I imagine the photographer positioning himself capture the shot in the midst of hordes scrambling to grab water, food, batteries, flashlights, fuel, candles, first aid items and toilet paper (TP) (yes, TP is incredibly valuable in an emergency though few people talk about stocking it up) in the supermarket.

Regardless of the country (developed e.g. Australia, developing e.g. Haiti, communist) and the type of disaster or emergency (flood, earthquake, civil disobedience, war), the same patterns are often observed.

The chain of event goes something like this (also see this earlier post on the earthquake in Chile based on similar themes):
  1. Dysfunctional  utitlitiesElectricity usually goes down. This has wide ranging implications as many other services depend on this modern convenience. And in the case of floods, the power company may turn it off to prevent accidental electrocution. Same goes for gas lines during an earthquake, the gas company turn them off to prevent explosions due to gas leakage.

    Water supply may or may not be disrupted. Even if your tap continues to run, the water may not as clean as before due to contamination at broken lines or inadequate treatment at the water works.

    Though fixed line phones are not directly tied to the electrical supply (i.e. your phone may still work even if your power is down), the physical cables and switches may still be affected by the disaster. In case you think your cellular phone has a better chance, don't count on it as the disaster can strike at the wireless transceivers placed around you. (Next time when you are outside, watch out for those usually grey boxes with 2 antennae hanging above you e.g. lamp post. There, you have your cellular transceiver.)

    Sanitation - big and ugly problem. What are you going to do if your WC stops working. Do you have a chemical toilet tucked away somewhere? Not likely. This is a very real problem yet few people want to come face-to-face with it (same as for TP).

    Not really counted as a utility but highly valuable and useful - money. Due to a lack of power or communications, forget about  using your credit card or debit card. Even cheques are viewed with suspicion. (Is your bank still going to operate after the flood/earthquake/emergency?) Cash is KING. And it pays to have small change and denominations for the small value items. By the way, your ATM is probably not working or out of cash.
  2. The mad rushPeople may initially be in a state of denial about the extent of damage. (Right, the government will fix things up. Or we can depend on the utilities companies to bring everything back to life within hours.) Once they wake up to the fact that our modern conveniences are not going to be back for some time, panic rushes in. Supermakets are raided for food, water.... Even items of dubious value (e.g. caviar) are cleaned up with all the cash one can master. If you are heading to the supermarket at the same time when the hordes are on a spree of panic buying, good luck.
  3. Civil disorderDepending on how strong the authorities are and how fast they can deploy policemen and soldiers, civil order may break down. (Remember, policemen and soldiers may also be affected by the disaster so whether they turn up for work is a big question.) When people go hungry and thirsty and uncomfortable (or worse still, their children are experiencing these problems), morality, legality and decency can go the way of the window. Riots, looting, burglary, kidnapping and daylight robbery crawl out of the woodwork. I added kidnapping because I have read of criminals kidnapping children in exchange for food and essential items from the parents during Hurricane Katrina.
  4. Health issuesIf normalcy is not restored soon (say days or weeks), the lack of clean water and food and adequate waste disposal (both liquid and solid) will take a toll on the population's health. Water borne diseases like cholera and typhoid are incredibly easy to spread among people packed together in refugee camps having less than proper sanitation. Dead bodies of humans and animals may lie (or float) in the streets waiting to be cleared. Add in malnourishment and you have the recipe for diarrhea and dysentry in addition to the big 2 above. Children and the elderly normally suffer the most. In the tropics, you can also count on vector borne diseases like dengue rearing its ugly head.
I am sure I can continue writing on and on but the idea is disasters suck. And they suck worst when you do not know of its consequences and/or are unprepared for them. (Yes, I have not written anything about the preparation part but that would be too much for a single post, right.)

Tuesday, January 04, 2011

Singapore latest water attraction - Sengkang Floating Wetland

I finally had the chance to visit this latest water attraction in Singapore. It is not in Sentosa but right in the middle of Punggol Reservoir surrounded by Sengkang, Anchorvale and Punggol housing estates. Publicised since at least 2007, the Sengkang Floating Wetland was finally launched in Nov 2010 by PUB (Public Utilities Board). See PUB press release 07 Nov 2010: Wet and Wild

Figure: PUB poster on "Sengkang Floating Island" (circa 2007)

Figure: A map showing the floating wetland (in green) in the middle of Punggol Reservoir with Anchorvale Community Club in the east and Sengkang Riverside Park in the west

What I found highly useful are the numerous signboards describing the wetland, how it works, the importance of the watershed (covering Punggol, Anchorvale and Sengkang) and the various water plants grown on the wetland itself.

Figure: This is probably the best take-home message from the signboards. It actually shows the delineation of the watersheds (light blue)for all 17 reservoirs (dark blue) in Singapore. Of particular interest are the white areas which represent non-watershed areas i.e. rainwater falling in these areas do not go into any reservoir. A good guess would be about 70% of Singapore's land area is used to collect rainwater. Another interesting point is Changi Airport area is NOT a watershed though the airport itself harvest rainwater for its own water demands. See previous post - How to reduce flooding in Singapore? Harvest more rainwater!

Now, a floating wetland is a kind of constructed wetland but unlike the traditional constructed wetland, it floats on the surface of a water body rather than acts as a container for the water body. Flotation is achieved using a mat of polymeric material which acts as a substrate for water plants to grow and at the same allows the roots to penetrate into the water column. PUB already has several of these floating wetlands (in a smaller scale) in other reservoirs - Lower Seletar, Pandan.
(Update: Sengkang Wetland is based on BioHaven floating islands which have been used in other countries.)

Figure: A mini floating wetland at Pandan Reservoir

Figure: A conventional constructed wetland in Mississippi (

Constructed (and floating) wetlands are usually designed to clean up the water, improving water quality. The roots and the underside of the polymeric mat tend to accumulate a layer of biofilm containing bacteria, fungi and algae which help in the decomposition of organic matter, nitrogen (e.g. ammonia) and phosphorus compounds. The water plants themselves also can absorb nitrogen and phosphorus, as well as certain heavy metals. Their roots extend into the water column not just for aesthetics but they can also filter and trap sediments. Such a use of plants to clean up the environment is known as phytoremediation. For a more complete discussion, check out this post - Before you write off a plant as a weed, read this

Besides the benefits of cleaning up water and providing a refuge for wildlife, a floating wetland has several advantages over a conventional constructed wetland. It is easily fabricated elsewhere and several units can be joined together to make a large wetland in actual deployment. It can be conveniently placed in existing water bodies without excavation and retrofitting of the existing landscape. If you find lake X has poor water quality, just push a few floating units into the lake. And when they have accomplished their tasks or if problems crop up, they can be conveniently removed as if they were never there in the first place.

However, a key design of constructed is the depth and width of the water body. For the plants (and associated biofilm) to work their magic, the water has to pass through the zone of influence of the roots. A lone floating wetland in the middle of a wide and deep river is not likely to have enough juice to clean up the river. I am not sure how deep the Punggol Reservoir is but if it is like most reservoirs, probably a few metres deep. I doubt the roots can reach to such depths. Also, when I look at the map of the Sengkang Floating
Wetland (see above), it appears exactly like a lonesome patch of greenery surrounded by a swath of blue. Can it really improve the water quality? If yes, how much? (As a side note, I may be conducting water quality monitoring workshops here so perhaps, the water quality data can provide a better picture.)

Anyway, water cleaning efficiency aside, Sengkang Floating Wetland is an excellent showcase of Singapore's focus on active, beautiful and clean water.

Figure: A boardwalk connects the floating wetland to the 2 banks and allows visitors to get up close and personal.

Figure: Viewing the floating wetland and boardwalk from Anchorvale CC. Notice Sengkang flats in the distance

Monday, January 03, 2011

Australia inundated by flooding

We seem to be seeing more flooding and at more serious intensities around the world these years. From New Orleans to Malaysia, Pakistan and now Australia, floods have had a busy decade. While some fingers point to climate change, others point to El Nino/ La Nina effects and still others decry the destruction of natural buffers such as wetlands and coral reefs as the culprit to widespread flooding.

The latest flood on the block:
Australia floods larger than France strand 200,000

"The muddy water inundating thousands of homes and businesses has led to a shortage of drinking water and raised fears of mosquito-borne disease...

The town was facing food shortages, power outages and sewage-contaminated floodwaters..."

And like all floods (and most natural disasters e.g. earthquake in Haiti, Chile), the victims are facing a shortage of clean drinking water, lack of sanitation services, contamination from wastewater (sewage) and water (and vector) borne diseases in addition to all the other inconveniences such as power outages, shortage of food and lack of shelter.