Water quality standards for rain garden

*Some private information in the original email have been edited out*


I have been tasked to work on the newly set up rain garden. I am basically testing the efficiency of the raingarden, i.e. is it able to effectively improve water quality of the influent stormwater before it gets discharged into the reservoir.

I have been looking through at both PUB and NEA's websites to get a set of water quality standards for the parameters that I am testing, i.e. 

 

i) E.coli

ii) Suspended solids

iii) Nitrates

iv) Phosphates

 

However, I have only been able to get the set of standards for drinking water which would not be ideal for my project as the standards or permissible limits is too stringent. 

 

So for the purpose of my project, I would like to know if there are standards that I can rely on for the above tests? 

I see some international standards on recreational water, drinking water, etc? But I am not sure what would the Poyan reservoir be considered as?

Some of the overseas standards that I found online show only certain parameters and in addition to that I find it very difficult to find a standard where the values remain the same for the different countries.

 

I hope that you will be able to assist me in some way possible.

Thank you.

 

Best Regards,

K


Dear K,


It's good to hear that you are working on a rain garden to improve the quality of surface runoff into our reservoirs. Over the years, the development of Singapore has removed much of our natural vegetation so seeing highly muddy waters (aka kopi susu) in our canals after a heavy rain is quite common.


As for your question, PUB tests against its own water quality standards within its reservoirs. Unfortunately, these standards are not available to the public.


2 possible options:

 

1. You can make use of NEA effluent discharge standards for a controlled watercourse (i.e. a waterway that flows into a reservoir). It monitors 36 WQ parameters as of this writing. Except for E. coli, they include the other 3 parameters that you are interested in.
2. Alternatively, you can use Nparks WQ standards for the water bodies under its purview. The standards were derived from WQ data observed in 59 different water bodies.  Regrettably, these standards are not available online as far as I know. Published by CUGE (I was a member in its technical committee to advise on their contents), the 2 relevant titles are:

Guidelines on Water Quality Assessment and Management for Tropical Ponds. You can check out my previous post on this title.

Guidelines On Water Quality Monitoring For Tropical Ponds

They are available from CUGE - https://www.cuge.com.sg/research/catalog.php

Their standards are not exactly the same as what you are interested in. The closest are:

1. Turbidity: < 30NTU
2. Total nitrogen: < 1.0mg/L
3. Total phosphorus: < 0.06mg/L
4. Enterococcus bacteria: < 200CFU/100mL

Good luck!