The curse on the waters off Pasir Ris

The waters off Pasir Ris seem destined to be cursed with massive fish kills now and then. Fish kills have been documented there for years! (See my previous posts on this topic.) The latest came as no surprise - Straits Times 1, 2; Today 3, 4; Channel News Asia (CNA) 5.

In response to an invitation from CNA to check out the waters there, a team of us headed down to the field for a quick water quality monitoring (WQM). It had been a week since the fish kill occurred so I was not expecting to see anything extraordinary in our WQM results. Nevertheless, it was a good chance to stretch those hands and legs on some good old field work.

Other than conducting field trips for my students as part of their curriculum, it has been some time since I have field work in WQM. For those following my blog, I had been involved in other aspects of water the past few years - rainwater harvesting, grey water recycling. Water is such a fascinating yet vast topic. It can cover indoors, outdoors, natural, industrial, agricultural, household, economics, political, war and many other areas besides.

Back to Pasir Ris... On 10 Mar 2015, we did WQ tests at 2 spots at Pasir Ris and 1 spot at Punggol for reference. Here is a summary of the results.

The number above may appear intimidating but worry not, below is a description in plain English.

Overall, the water quality looked pretty good for all 3 locations. A few points:

1.       The water at Pasir Ris has become somewhat saltier compared to my data in 2010.

2.       The water has also become somewhat more alkaline compared to my data in 2010.

3.       The water is significantly clearer (less turbid) compared to 2010. Less construction work going on?

4.       Nutrients (ammonia, nitrate, phosphate) are significantly less compared to 2010.

5.       Bacterial counts are significantly less compared to 2010. Can we all swim there now?

6.       Pasir Ris spot 1 appeared to have a slightly higher bacterial count compared to the other 2 locations. FYI, spot 1 is where a great deal of dead fish were washed up the previous week.

 Don't forget, about a week has passed since the fish kill. Don't expect to see problems in the water quality during our field trip or we will still be seeing dead fish on the shores for the entire week - a scary thought.

Figure: WQM team at work at Pasir Ris

Figure: The cozy CNA van that brought us and our equipment around our test sites

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.



Is Pasir Ris water really unsafe?

As a follow-up to the news update on the fecal bacteria laden water of Pasir Ris, this news may throw more questions (instead of light) on the issue of poor water quality at Pasir Ris.

First, a quick summary. A press release from NEA (Sep 2010) stated that the water at Pasir Ris Beach is unsafe due to the off-specs level of Enterococcus (a bacteria) in the water. Enterococcus is supposed to indicate the level of fecal contamination. More Enterococcus of course means more fecal contamination, implying a higher possibility of the presence of human pathogens.

Why don't we analyse the water directly for the pathogens? There are simply too many pathogens to test for so going down this route will easily lead to a logistical nightmare. Therefore, we stick to an indicator organism, something that is strongly linked to humans. Since Enterococcus (supposedly) comes from the human gut, its presence is (supposedly) sufficient to prove the contamination of the water by humans.

Going back a bit backwards in the history of water quality testing, the title of indicator organism for fecal contamination used by held by a group of bacteria known as coliforms. Not surprisingly, coliforms are also found in the human gut and its presence used to conclude the presence of human contamination. Unfortunately, coliforms are also found in other animals and soil. Some years back, Enterococcus has taken over this position as it was found to produce a better correlation to many human pathogens found in sewage. (Opps, the summary seems a bit longer than I initially thought.)

Ok, enough of summarising. Check these out:
1. Evaluation of Chemical, Molecular, and Traditional Markers of Fecal Contamination in an Effluent Dominated Urban Stream

2. How To Define "Safe" Water? Water Pollution: Southern California study highlights the limits of bacteria used as fecal indicators

The study basically argues that even Enterococcus is not a good enough indicator for fecal contamination in water. Why? Because it can also be found naturally in the river bed (in the study). In fact, it can actually grow in the river bed under favourable conditions i.e. good nutrient availability. Therefore, a bacterial count using Enterococcus tends to be overestimated with regards to the actual fecal contamination. (Granted, the study took place in fresh water and not seawater. But being such a versatile creature, Enterococcus can tolerate a wide range of conditions - pH, temperature, salinity, presence/absence of oxygen so it will not be surprising to find it thriving nicely in seawater.)

Is the water at Pasir Ris safe then? Your guess is as good as mine.

However, the study did recommend a substitutre for Enterococcus - something known as human-specific HF183 Bacteroides. This bacteria is supposedly (?) found only in the human gut. Testing for the presence of its genetic material will provide an accurate (?) picture of the amount of fecal contamination in water.

Will it really work?

Me? I will wait for the next piece of study to throw a spanner into this theory :-)

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.

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.

Fish kill at Pais Ris: do you have a million bucks to spare?

Apparently, the recent fish kill at Pasir Ris (Dec 09) and Pulau Ubin (Jan 10) was not the only event concerning negative water quality in that area.

Other events include:

1. 2008, 2009 - Pasir Ris Beach was found unsuitable for swimming because of the high bacateria (Enterococcus) count
2. Dec 2006/ Jan 2007 - mass death of marine creatures in Chek Jawa due to drop in salinity caused by heavy rainfall
   (Update: a comment from "Death Note from Chek Jawa" recorded the salinity at 22ppt (parts per thousand). I believe this was  measured using a portable conductivity meter. I personally find measuring the salinity this way can be rather confusing to readers as the salinity is calculated by the meter based on the conductivity multiplied by a conversion factor. Unfortunately, this conversion factor can be quite different for different waters, ranging from 0.5 to 0.7. Hence, I personally find it more useful to report the salinity as the base measurement of electrical conductivity adjusted to 25oC.)

According to AVA, a monitoring programme has already been in place to test the water quality in the said area. Without elaboration from AVA about its programme, I shall not comment on its effectiveness but here are my suggestions for AVA/NEA for a price tag of (you got it!) a million bucks.

Since this Pasir Ris/ Pulau Ubin/ Changi is such a problematic area in terms of water quality, install a continuous monitoring system with maybe 3 to 5 monitoring stations to provide real time data for immediate response. The technology is there... you just need money. Even manpower is saved since staff only go down to the field for further investigation or to do sampling for a more detailed analysis.

1. 3 - 5 buoys containing water quality and metereological sensors, telemetry package, solar panels and batteries. See previous post. They should be strategically placed for maximum monitoring effectiveness - 1 at north of Pulau Tekong, 1 south of P. Tekong, 1 between P. Tekong and P. Ubin, 1 north of P. Punggol and 1 north of Pasir Ris Beach
2. One/two water quality sensor packages installed on each buoy. See previous post. They should be able to measure depth, dissolved oxygen (DO), turbidity, electrical conductivity (EC), temperature, pH, chlorophyll, nitrate, ammonia. I was told that each package can cost about S$15000.
3. Remote server (perhaps in the agency's HQ) with the capability to receive data via cellular signals from the buoys/sensors.
4. To handle these vast amount of water quality data, GIS (geographic information system) should be installed on a workstation linked to the remote server to document and analyse the data. See previous post. A GIS can also provide a visual display of the water quality with colour coding. Any unusual or out-of-spec event should trigger an alarm. 
5. Better still, install a modelling software to tie in with the GIS. Some free models can be found at USEPA. A properly calibrated model can make predictions and simulations on the water quality in the area to prepare for future events of similar or worse magnitude.
6. Qualified and trained manpower to use and maintain all the above goodies.

All the above may not even amount to $1M. I am sure this system will reduce the guesswork involved in future events e.g. whose fault? and probably allow for rapid remediation if required.

Some thoughts on the fish kill at Pasir Ris

I must admit I have not been following the news about the recent fish kill at Pasir Ris as close as I should have. But thanks to Ria, her blog posts quickly brought me up to speed on the sequence of events. Here are the links with further links inside the webpages.

1. Dead fish patrol: Pasir Ris
2. Any dead fish at Changi?

From all accounts, the situation appeared to be a classic case of eutrophication. Put simply, eutrophication is an excessive growth of algae (sometimes, the term plankton is used though they are not the same) caused by the introduction of nutrients into an ecosystem. Depending on the type of algae, the nutrients may be nitrate, phosphate, silica or others.

Without further information from AVA (or NEA which was strangely silent in this whole episode) about the kind of algae (or "plankton" as given in the media) in the seas off Pasir Ris, I can only surmise that nitrate and ammonia (which can degrade to nitrate) are the probably culprits. In general, seawater is limited by nitrogen so once a sudden excessive input of nitrogen (in the form of nitrate or ammonia) rushes in, the algae immediately makes the best of this bonanza to multiply.

Nitrate is commonly found in fertilisers (yes, it is good for plants too!) and sewage (an decomposition product of ammonia). The question is: who was releasing these fertilisers or sewage? One suggestion was the incidental heavy rains have washed fertilisers or sewage into the sea. Of course, the question remains: where did these fertilisers and sewage come from?

Algae grows fast but they die fast too. Dead algae is major bad news as they decompose, using up dissolved oxygen (DO) in the water. Since many marine organims can only breathe DO, they are in trouble. However, marine organisms are not created equally. Some are more hardy than others since they need less DO to survive.

Wouldn't oxygen from the air replenish the loss of DO in seawater? Yes, it would but the rate of replenishment lags far behind the rate of DO usage in decompostion. Imagine lots and lots of algae dying and taking up DO. Atmospheric oxygen wouldn't have a chance!

Figure: Eutrophication at Botanic Garden (Nov 08). The greenish water is a dead giveaway.
Monitoring by AVA
According to AVA, regular monitoring was in place even before the recent fish kill event (Straits Times Forum 11 Jan 10). When the fish kill occurred, its staff was monitoring daily.

It will be great if AVA can reveal more about its regular monitoring programme - how regular? where are the monitoring stations? What kind of data are collected? For its daily monitoring during the fish kill episode, in addition to the above questions, can AVA reveal the following - what kind of algae was detected in the bloom? Was there a spike in the nutrient levels? What kind of nutrients? What is the trend for DO during the monitoring period?

What about NEA? It has many water sampling stations along the coast. Can their data shed any light on the fish kill? For that matter, NEA has never elaborated on its monitoring programme either i.e. kind of data collected, frequency of collection. Its water quality results have never been in the public domain (except for bits and pieces in its annual report.) (That goes the same for PUB. Have you ever tried requesting for a copy of the analysis report of the tap water that goes to your house?)

Figure: NEA sampling stations in both inland and coastal waters (taken from NEA website a few years back as it no longer could be found currently)

For some reason, water quality data are considered confidential in Singapore. Do such data constitute an issue of national security? Or are the agencies concerned about a vulnerability in their legal position?

Check out the extensive data placed online by the Environmental Protection Department (EPD) of Hong Kong.

Or the data compiled by USGS (U.S. Geological Survey) for the USA.