Wednesday, October 24, 2012

Green project part 3: Integrated rainwater harvesting and grey water recycling systems

You may click on these links for part 1 and 2 of this green project.

After months of planning, sourcing, talking to vendors etc., the prototype for the rainwater harvesting (RWH) and grey water recycling (GWR) systems is up. This prototype combines both systems into a single framework (pun intended) and is intended for testing the components and process flow as a coherent whole. Though the final design in the "actual" project will appear very different, this prototype and the actual system basically share the same elements and process flow.

Our SP Library has kindly allowed the prototype to be placed in their garden for testing. Bravo to them!

Figure 1: Figure shows the mini grey water recycling system incorporating  plants as the "filters" in 3 separate cells. In the background, you can see the book shelves of the library. If this prototype proves successful, it may be placed as it is for the long term as an educational tool for our students. Posters will then be fixed strategically to explain the capabilities of the system and how it works.
Figure 2: To polish up the grey water and the rainwater, off-the-shelf filters are installed. Depending on the quality of your input and the desired quality of your output (what do you want to use your treated water for?), these filters may not be necessary.

Saturday, October 13, 2012

Water quality monitoring workshop for CUGE (Centre for urban greenery and ecology) 2012

I just had another round of running the water quality monitoring workshop for CUGE (Centre for urban greenery and ecology). Attended by mostly Nparks staff and some staff from private companies, it was great fun to run this workshop. I suppose doing something you like is always fun, despite the sweat poured into its preparation (think logistics e.g. are you sure you have brought the right gear in enough quantities to run your course?) and the actual execution.

The workshop was run pretty similar to the one last year.

One notable exception was the use of iPads as data collection devices in the field. Water quality (WQ) data was keyed in directly into the iPad, forgoing the step of writing on pieces of paper that tend to get wet, muddy and folded out of shape. (Hey, with a seven hundred dollar iPad in your hands, you too would take tender, loving care of it.) Despite what you may think, I am not using it for the WOW factor or because it is the IN thing.

The main advantage of using an iPad is having a customised app (kindly designed by my colleague in SP's education department) to transmit the water quality data to a central server. One, all WQ data can be kept in one spot for easy reference in the future. Two, having a standard template (as an app) allows different users to key in data in a fixed format - no need to struggle to interpret whether this test was done once or twice or what the units were supposed to be. Imagine letting loose a group of students (or interns) to do WQM (water quality monitoring) in the field with only simple training and minimal supervision. Data collection will become immensely efficient. (Nevertheless, I must emphasise that these students be trained in the proper monitoring and sampling techniques lest they collect irrelevant or unusable data.)

Figure 1: The compulsory group photo taken at Graffiti Bridge along Ngee Ann Stream

Figure 2: The seldom taken group photo at the end of the workshop at Botanic Gardens

Figure 3: iPad app for water quality monitoring data collection

Figure 4: Screenshot from the server showing the WQ data since the system was started

Tuesday, October 09, 2012

Overseas community service (OCS)/ Youth expedition project (YEP) part 1: Is that water safe?

Our students are really lucky these days to have many opportunities to go overseas. We have acronyms like YEP (youth expedition project) (funded by MCYS), OCS (overseas community service), OCIP (overseas community immersion programme), OITP (overseas industrial training programme) plastered around campus, encouraging our students to sign up. In addition, we have more of the overseas outdoors variety of activities e.g. leadership camp, adventurers camp, mountain climbing, too.

Especially for YEP/OCS where the participants (students & staff) get to live close to the community they serve (read rural and undeveloped), they will stand next to the pond/stream/cistern/faucet/pail (take your pick) and ask, "Is that water safe?" Unfortunately, the answer may not be so straightforward.

Let's answer that question with another question, "Safe for what?"

For the brevity of this post and the significance of the intended use, let's restrict ourselves to "safe for drinking".

Water quality (WQ) parameters
If you are going to test the water according to WHO drinking water guidelines (more about the testing of water in an earlier post), you are going to find yourself wading in deep cess. You have close to 200 WQ parameters to test and the a complete set of tests will burn a big hole in your pocket. Fortunately, I can share some tips here to make your judgement easier or at least drastically reduce the kind of tests you need to make.

Sources of water
  1. Rainwater
    This is the cleanest form of natural water. The processes of evapotranspiration and condensation in the water cycle is effectively a form of distillation. The only concerns will be air pollutants (e.g. acid gases, particulates). Acid gases will of course make the water acidic while particulates may contain heavy metals that go into rain. But the effects are likely to be small compared to the potential problems encountered in the next few sources. Hence, I would still put my bet on rainwater as a viable drinking water source among the various natural sources. This is also why I strongly advocate rainwater harvesting in communities that lack a reliable and safe source of drinking water.
  2. Surface water: Pond, stream, lake
    I would check (ask the locals, check the map etc.) the upstream and the surroundings. Are there residences, industries, agriculture or other human activities? These can release human waste, animal waste, industrial waste, pesticides and other nasty stuff. Unless near the headwaters (usually thick jungles in the tropics), surface water tends to be turbid and contains an unhealthy does of bacteria. These are 2 good WQ parameters to measure if you still want to use surface water (perhaps combining with some sort of treatment). And if there are industries and agriculture around or upstream, you can add heavy metals, pesticides, oil, detergents, fertilisers into your to-do list of WQ testing.

    (Digression: Incidentally, I have seen outdoor activities being conducted with the participants immersed in a river (i.e. primary contact) in other countries. Hopefully, the organisers have bothered to check what is upstream of that river in case the participants gulp down mouthfuls of river water containing human waste from the village upstream.)
  3. Groundwater: well, spring
    Generally less turbid and has less harmful bacteria than surface water. However, it may contain heavy metals (e.g. lead) that occur naturally in the ground. Depending on presence of arsenic deposits in your area (developed countries e.g. USA are not spared either), your groundwater may contain a dangerous concentration of arsenic.

    On the other hand, the presence of human activities e.g. industries can also lead to leaching of toxic chemicals (think organic solvents, pesticides, electroplating wash) into groundwater. This is especially true if the industry does not have a habit of cleaning up their act e.g. dumping waste into the ground like nobody's business instead of treating or sending it for proper disposal.
  4. Man-made outlet: faucet, cistern

    Hey, the water must come from somewhere right? Is rainwater harvested and stored in the cistern? Or is there a pipe that conveys the water pumped from a well or stream? Maybe the nearby spring is diverted to come out from the faucet?

    Make the effort to find out the origins of your water and see if they come from any of the above 3 sources.

    Finally, your community/village may be lucky enough to have piped water from a water treatment plant! This may or may not be good news though. For one thing, it is hard to tell if the water treatment plant is doing a good job without doing any actual WQ testing. The locals may be able to advise you but then again, their bodies may have adapted to the water (clean or otherwise) and some effects do not appear in the short term.

    Note that not all water treatment plants are built alike or at least they are not built like our PUB plants which are considered effective and produce water of adequate drinking standard. I have heard of water treatment plants in other countries that add massive doses of chlorine to kill the germs but do little else to clean up their water. Well yes, you have germ free water but that heavy dose of chlorine will probably give you cancer years down the road.
I will continue in more future posts on this topic

    Figure 1: Sand filter at our local water treatment plant at Chestnut Drive (see previous post).

    Figure 2: Binjai Stream - this part is close to the headwaters so the water is relatively clean and clear, flowing over a sandy bed.

    Figure 3: Ngee Ann Stream - this is further downstream from the headwaters. Note the obvious turbidity.

Thursday, September 27, 2012

How are total dissolved solids (TDS), salinity and electrical conductivity (EC) different?

This is one of those details that we don't pay much attention to. We have a vague idea that TDS, salinity and EC are somewhat different yet most of the time, we treat them as the same creature. Well folks, they may be in the same happy family but they are certainly not the same family member.

Ok, here is a quick introduction.

Electrical conductivity (EC)
EC is easily and cheaply measured by a sensor consisting of 2 electrodes. A potential difference is applied, a current flows between the 2 electrodes and the conductance (reciprocal of resistance) in Siemens (formerly mho) is measured. The conductivity is determined by multiplying conductance by the cell constant (a property of the sensor; = electrode distance / surface area) in cm-1. Since a Siemen is a pretty large value, most fresh waters have EC in uS/cm while brackish and salt waters have EC in mS/cm.

Naturally, the higher the amount of ions (i.e. dissolved salts) in the water, the easier it is to conduct electricity by ion transport and the higher the EC.

Total dissolved solids (TDS)
Theoretically, TDS refers to the total mass of dissolved solids (most inorganic and some organic stuff) in a given volume of water.

One way to measure TDS is to filter a known volume of water through a standard glass fibre filter, vaporise the water in a steam bath, dry at 180oC and weigh the remaining solid residue. If you are testing fresh waters, you are going to need a lot of water (figure at least 1L). If all these steps sound tedious, you are right. You also need to wait while the drying takes place. Definitely not suitable for achieving instantaneous results. Also, note that the drying step may remove a portion of some substances e.g. chloride, organics.

Nowadays however, TDS is commonly measured using sensors (easily, cheaply and instantaneously). Or is it? If you religiously go through the instruction manual for your TDS instrument (meter + sensor/probe), you realise there is usually a user defined parameter known as TDS constant ranging between 0.3 - 1.0 (range varies depending on instrument brand and model). OMG, what is this? What value should I use? Thankfully, the instrument is usually set at a default, say 0.65. Not so thankfully, this TDS constant can be awfully important as its value depends on a the type of water sample. Unfortunately, most people will not go into such details when measuring TDS.

Basically, TDS (mg/L) = TDS constant * EC (uS/cm)

The above formula only works if you use the correct TDS constant for your water. Fresh water may have a constant of 0.65-0.7 while seawater is better off at 0.5 because they have different compositions! Seawater is mostly sodium and chloride. Fresh waters can have vastly different compositions depending on the geology and other factors. How good is the value you are using or do you even know what value you are using?

To make matters worse, some smart guy came up with salinity as a water quality parameter. Even without complicating TDS, salinity by itself is slippery to define.

Originally, it refers to the amount of dissolved substances (including gases) in a given volume of water. But in practice, this definition is difficult to quantify e.g. gases are lost easily, some chloride can be lost during drying.

Therefore salinity is redefined using chlorinity.

S = 1.80655 Cl
where C = "the mass of silver required to precipitate completely the halogens in 0.3285234kg of the sea-water sample"

With the advent of EC sensors (did I say that they are easy and cheap to use?) which far surpass the cumbersome nature of chemical methods, salinity of seawater was once again redefined based on EC.

S = 0.0080 - 0.1692 K15 1/2 + 25.3851 K15 + 14.0941 K15 3/2 -7.0261 K15 2 + 2.7081 K15 5/2

K15 = C (S,15,0) / C (KCl,15,0)

where C (S, 15, 0) is the conductivity of the sea-water sample at a temperature of 15°C and standard atmospheric pressure, and C (KCl, t, 0) is the conductivity of the standard potassium chloride (KCl) solution at a temperature of 15°C and standard atmospheric pressure. The standard KCl solution contains a mass of 32.435 6 grams of KCl in a mass of 1.000 000kg of solution.   If all the above sounds profound, don't worry. Your isntrument should be able to perform the calculations for you automatically behind the scenes without your intervention.   Please note that the historical development of salinity above is a simplification. There are more intermediate development stages not described above.     What is the verdict then? My verdict is...... just measure in EC!   EC is the basic parameter measured by your instrument. Though many instruments proudly proclaim that they can measure EC, TDS and salinity at the same time, TDS and salinity are simply derived parameters and not measured directly.   How would I know whether my peat swamp should be using the same TDS constant as my storm water canal? They probably should not since the composition of each is likely to be different.   For that matter, the salinity above works because it is designed for seawater which amazingly does not vary much in the ratio of its consituent ions (sodium, chloride, sulfate, magnesium, calcium, potassium) from location to location. You definitely can't bet the same for fresh waters.   Basically comparisons of TDS and salinity become meaningless when the compositions of the water samples are quite different. Therefore, why go to the extra trouble of measuring TDS and salinity when you can do with EC? (Of course, salinity is still quite suitable for measurement in seawaters for reasons mentioned above.)  
Figure: A typical hand-held EC probe (meter + sensor (right end)) often used for my water quality monitoring activities. This particular model is only good for fresh waters.

Figure: A more elaborate set-up that can "measure" EC, TDS & salinity. The meter is at the bottom with the probe/sensor on top. This is suitable for fresh to brackish and salt waters

Friday, May 04, 2012

My current green project part 2: rainwater harvesting system

Here is the 2nd part of my involvement in a major green project in the form of a mindmap presented to the participants of the project. The green technology here harvests and treats rainwater to a suitable quality for further use. Similar to the previous post, it touches on the design considerations for builidng a rainwater harvesting. (Click on the figure on look at the whole map.)
Fore more on rainwater harvesting information, refer to my previous posts here.

Wednesday, May 02, 2012

My current green project part 1: grey water recycling system

Here is the mindmap which I presented to a group of participants for a major green project we are working on. (Sorry, can't reveal much detail at this point of time.) It contains the important design considerations for a grey water (i.e. water from the sinks, shower, laundry BUT not the W.C.) recycling system inherent in the project. (Click on the figure on look at the whole map.)

 Figure: Possible candidate for the plant treatment cell - Canna Lily. This is an example of phytoremediation - using plants to clean up the environment.
Figure: Another possible candidate for the plant treatment cell - Heliconia sp. Both candidates are easily available in Singapore as they are extensively used in landscaping.

For more information on phytoremediation, refer to my previous posts here.

Sunday, April 01, 2012

The ABCs of self-publishing your own book

I had the pleasure of giving this talk on my experiences of writing a book on water quality monitoring (WQM) - Your first guide to WQM in Singapore, to my fellow staff in SP. See previous post for more information on my book.

Some advice here for budding writers out there.
  1. If you are writing about your experiences, it is important to document them. For me, this blog is my documentation of my WQM activities. When the time comes for you to write, referring back to your documentation is immensely easier than recalling your  memories from scratch. Trust me on this.
  2. Royalties (if any) make everything more tricky than they should be. Discuss with your management, collaborator, sponsor and other stakeholders well beforehand.
  3. Perhaps the best take-home message is: personalise your writing whenever possible. The reader prefer contents close to his heart with a fair bit of personal touch. Otherwise, your book will just become another piece of academic text. For example, if you want to stress about the importance of safety, it is far better to describe how a student got stuck in mud and almost became crocodile fodder. (Kidding on the croc part)
  4.  Figure: Going barefoot to brave the mud in Nee Soon Freshwater Swamp. Not a good idea...
    (Updated on 20/2/13: Nee Soon Swamp Forest is a highly sensitive area that is off limits to the general public as the biodiversity may not be able to handle the visitor load. Special permission from Nparks must be obtained prior to entering the area.)
Figure: Wearing wellies (high water boots) does not guarantee you won't be touched by mud but at least your feet are well protected.

Friday, March 30, 2012

Request for additional information about Punggol and Serangoon Reservoirs

* Parts of the email have been removed for conciseness*

I read with interest about the blog posts which you have made about the newly opened Punggol Reservoir as well as the overall knowledge that you have about water quality monitoring. Given your enthusiasm and expertise in this field, we hope that you will be able to furnish us with some of the details that we require, such as:

- An overall idea of the environmental monitoring process

- The critical parameters which are monitored and their baselines [understand from Greenspan that, for water, this includes: Dissolved Oxygen (DO), Temperature, Turbidity, pH, Conductivity, Chlorophyll-a and Nitrate (NO3)]

- How often/when are samples collected for testing?

- Are there any typical steps taken if the baseline conditions are exceeded?

It would be beneficial if some of the information are specific to the Punggol/Serangoon Reservoirs.


Like all other reservoirs on mainland Singapore, Punggol and Serangoon Reservoirs (PSR) are under the purview of PUB. The water quality in these reservoirs is definitely monitored though little detail has been publicised - type of water quality parameters monitored, frequency of monitoring, results and implications of the water quality data.

You may want to try the following reference books to find out more about water quality monitoring
  1. Water quality monitoring : a practical guide to the design and implementation of freshwater quality studies and monitoring programmes, edited by Jamie Bartram and Richard Ballance
    I find it useful as it covers the topic comprehensively though it may be slow reading at times. Published on behalf of United Nations Environment Programme, World Health Organization
  2. Water quality assessments : a guide to the use of biota, sediments, and water in environmental monitoring (2nd ed), edited by Deborah Chapman
    This is a follow-up to the above title. Again, useful and comprehensive. Published on behalf of UNESCO, United Nations Educational, Scientific, and Cultural Organization, WHO, World Health Organization, UNEP, United Nations Environment Programme

You are indeed right. Dissolved oxygen (DO), temperature, turbidity etc. are relatively easy to measure and hence routinely monitored, probably around once a week (my estimate, feel free to dispute).

I am sure many other parameters are also measured. (Just look at the WHO drinking water guidelines - they have about 200 parameters.) For example, heavy metals, pesticides, oil, volatile organic compounds (VOCs) are good bets. Even the fancy ones like dioxins and radioactivity are possible candidates. Of course, the frequency of monitoring of these chemicals (and radioactivity) depends on the cost and effort of analysis (e.g. expensive lab instruments or tedious lab preparation steps are needed), the likelihood of these chemicals existing in our reservoirs and their impact on health and environment. I won't be surprised if some of the fancy parameters are measured only once a year.

The parameters monitored in our reservoirs probably exceed those given in WHO drinking water guidelines. And PUB is probably going into biological monitoring using macroinvertebrates (bugs). Check out my previous post, Water trends in the next decade, for more information on this topic.

Figure: Serangoon Reservoir with a dam in the distance. The dam serves to separate fresh water in the reservoir from salt water in the sea.

Figure: Punggol Reservoir with Sengkang Floating Wetland in the foreground

For water quality monitoring  (WQM) in our reservoirs, setting up limits for the water quality parameters can be a bit tricky. Do we apply drinking water guidelines to reservoir water? Probably not.

Or do we apply guidelines for aquatic life? Countries such as USA, Canada etc. already have such guidelines. Do we use their guidelines? Again, probably not as the environmental conditions are quite different between Singapore and say, USA. Even if we develop our own guidelines, I am certain every reservoir will be different from one another e.g. geology. How do we factor these differences into our guidelines? Hence, I always believe that baselines for each reservoir will have to be established based on long term WQM. Any deviation from those baselines may then be further investigated. As far as I know, PUB's guidelines (if any) for reservoir water quality have never been publicised.