Monday, May 21, 2007

Prof Collignon on Recycling in Singapore

Prof Peter Collignon has provided us with some further commentary on the issue of indirect potable water recycling, particularly as it relates to a current proposal in Canberra. Once again there are a couple of direct questions posed by Prof Collignon. I have briefly responded to these by private email, but will also post a response here (now I’m relegated to the comments section of the blog!).

As always, I’d be keen to also receive your comments...

Date: Mon, 21 May 2007
From: "Collignon, Peter"
To: "Stuart Khan"
Subject: FW: Singapore drinking water contains very little recycled water from sewage

Dear Stuart,

You might be interested in this [email to members of the ACT Legislative Assembly] for your website (including the next few paragraphs). I would also value your opinion.

My view is that what Singapore is doing with recycled water seems eminently sensible (other than their token addition of 1% to their potable water - not sure why they even do that as 1 % is so small). My view remains that recycling water into drinking water should be a last option to overcome water shortages, not a first option as is the case with the Canberra proposal. In Singapore they seem to have taken a less risky approach. They take their high quality recycled water and use it for industry. This means that less water is thus taken form their potable supplies (ie they have substituted this recycled water for what would otherwise have been used from their drinking water sources). In Brisbane that would also make sense if the proposed recycled water was used for say their power stations and industry (and maybe irrigation) using separate pipelines (as is the case in Singapore). In Canberra I think we should use recycle water from sewage for instance to keep Lake Burley Griffin filled and for irrigation purpose eg keeping parliament house surrounds green, instead of using potable water for these purposes which is currently the case.

My basic presumption remains that when we recycle water (particularly from sewage ) because we can never have a system that will not have a risk of failing at some time, that we should use this recycled water for purposes where the health risk is lower if something should go wrong (eg industry, irrigation etc). We should not put it into drinking water unless there are no other reasonable options. Recycling water from sewage into drinking water is defined as a "high" or "very high" risk by the Australian drinking water guidelines (the chance that that the process will go wrong may be very low but because the consequences are very significant to large populations it become "high" risk).

Also I can't find any cities that I think are the equivalent of Canberra re the proposals here. Do you know of any good epidemiological studies that have data on the safety issue of recycled water from sewage in reasonable populations?

Peter Collignon
Infectious Diseases Physician and Microbiologist
Director Infectious Diseases Unit and Microbiology Department, The Canberra Hospital.
Professor, School of Clinical Medicine, Australian National University.

-----Original Message-----
From: Collignon
Sent: Thursday, 17 May 2007 10:21 PM
To: [members of the ACT Legislative Assembly]
Subject: Singapore drinking water contains very little recycled water from sewage

Dear Members of the Legislative Assembly,

I think that a few of you were surprised (and probably a bit sceptical) when I sent around a previous email stating that water from sewage was not recycled into the drinking water of Singapore to any significant extent. The common perception here in Australia seems to be that large amounts of water recycled from sewage are consumed in Singapore.

Since I sent my previous email I understand many of you have received emails, personal contacts or had material sent to you suggesting what I sent to you before and stated previously was incorrect on the Singapore water situation.

Below and attached are a number of different sources that allows you to independently check on the accuracy of my statements.

Hardly any (1% or likely less) of potable water in Singapore comes from recycled sewage (it seems to be mainly used by industry and is delivered by separate pipelines to drinking water and at a lower price). Thus looking at Singapore to establish any adverse health effects from this process in their population will be impossible as they hardly drink any of this type of recycled water.

Currently only 1% of Singapore potable water is recycled.

My sources for this are three different ones plus the Singapore water website (accessed today)

How will NEWater be used?

A. We will continue to use NEWater for direct non-potable purpose by industries, commercial buildings, etc. As for Indirect Potable Use (IPU), 3 million gallons a day of NEWater, about 1% of the total volume of water consumed daily, has been blended with raw water in our reservoirs. The amount will be increased progressively to reach about 2.5% of the total volume of water-consumed daily by 2011.

See also the attachments.

The first is an 2005 application form for NEWater that clearly shows there are two different pipelines and recycled water is kept separated from potable water (at least in 2005 it had said it is NOT for potable use).

"As NEWater is for non-potable use, customers will have to provide separate pipework for potable and non-potable water supply within their premises."

The 2nd source is a Financial Times London article. "In Singapore, it is a political choice designed to reduce dependence on supplies from neighbouring Malaysia - and accounts for less than 1 per cent of water consumed."

The third source is a 2007 publication from a group at the Uni of Queensland (who I understand are in favour of recycling sewage water for drinking - but see their excellent summary of other places that use recycled water). They give Singapore as an example and say “small portion” into reservoir; page 30). This group also has figures and comments on the very high-energy costs of this reverse osmosis proposal (see page 19).


Anonymous said...

Relegated to the comments section of which blog?

Stuart Khan said...

This one. I just meant that Prof Collignon would take up most of the body of this blog post and I would respond in the comments section. Sadly for me, I have a terrible flu at the moment and went to bed last night at 8 pm. But I will knock something up today.

Stuart Khan said...

The use of recycled water for industrial purposes is indeed eminently sensible. Australia and Singapore have really been world leaders in this arena. Consider some of the excellent schemes supplying significant volumes of very high quality recycled water to industry in Wollongong (Blue Scope Steel), Perth (The Kwinana industrial estate) and Brisbane (BP Amaco Refinery).

As all readers would know, the developing South East Queensland scheme involves providing water to two coal-fired power stations (Tarong and Swanbank) to replace their use of water from the Wivenhoe system. We’ve discussed the use of recycled water by power stations in Australia previously. Its very likely that some water will also be used for agricultural purposes. The remainder will be used to replenish raw drinking water supplies.

The ideal industrial users to identify for any particular scheme are those which will use large volumes of water, are located close to the source of recycled water, would otherwise compete for potable water supplies, and can be supplied in single pipeline (as opposed to a network of pipes). It would be great to receive any suggestions from readers regarding other suitable direct-supply users in SEQ. Prof. Collignon’s Canberra suggestions of Lake Burley Griffen and irrigation around Parliament House appear sensible, but it would be useful to know how much potable water these applications currently use and (pardon my ignorance) how close they are to potential supplies of recycled water. One limitation of allocating the recycled water to lawn irrigation is that this is a use that you lose when you most need it (ie during severe water restrictions). It would be preferable to allocate the recycled water to a use that would otherwise still place a significant demand on potable water use during restrictions.

Singapore authorities emphasise that recycled water supplied for industry is for non potable uses and thus segregated pipe systems are required. This is not surprising and is consistent with industrial water recycling schemes throughout the world including Australia. The water that is supplied for industry has not been through a drinking water treatment plant. Thus it is not deemed suitable for drinking. The smaller volume (~1%) that has been through the reservoir and through the drinking water treatment plant is perfectly suitable for drinking.

Prof Collignon states: “Recycling water from sewage into drinking water is defined as a "high" or "very high" risk by the Australian drinking water guidelines (the chance that that the process will go wrong may be very low but because the consequences are very significant to large populations it become "high" risk)”.

This is Prof. Collignon’s interpretation of the ‘risk matrix’ provided in the Australian Drinking Water Guidelines (and in many other risk-based guidelines). The risk matrix requires risk assessors to consider the combined implications of the ‘likelihood’ and the ‘consequences’ of a potential hazardous event. Doing so provides a ‘risk rating’ of low, medium, high, etc..

One disadvantage of the risk matrix is that it is quite qualitative in the nature of the ratings that it provides and thus very open to interpretation or opinion. However, I feel that Prof. Collignon’s use of the risk matrix is overly simplistic and thus incorrect. His simplistic approach would be expected to deliver a risk rating of “high” or “very high” for any water source whatsoever. In other words, while the likelihood of something going wrong is very low, the consequences are potentially devastating. But this is not an appropriate use of the matrix (which is fortunate or cities may have to cease delivering potable water!).

The risk matrix should be used to evaluate risks posed by the occurrence of specific “hazardous events”. A hazardous event may be something such as a high rainfall period, a failure of reverse osmosis pump, a loss of electricity to the treatment plant, a cross-connection between potable and non-potable water supplies, etc. Only once such an event is identified can the risk matrix be used to evaluate it. Risks associated with hazardous events that are not assessed as ‘low’, require the institution of additional barriers or management practices until a ‘low’ risk can be determined. The risk matrix is a planning tool intended to ensure that planners and scheme operators identify the sources of risk in their systems and manage them effectively with multiple barriers.

Prof Collignon asked “Do you know of any good epidemiological studies that have data on the safety issue of recycled water from sewage in reasonable populations?” There are a number of epidemiologic studies described in the Health Effects report that I prepared with David Roser. I have specifically directed Prof Collignon to those undertaken in Los Angeles:

Frerichs, R. R. (1984) Epidemiologic Monitoring of Possible Health Reactions of Wastewater Reuse. Sci. Total Environ., 32(3), 353-363.

Frerichs, R. R., Sloss, E. M. and Satin, K. P. (1982) Epidemiologic Impact of Water Reuse in Los-Angeles County. Environmental Research, 29(1), 109-122.

Sloss, E. M., Geschwind, S. A., McCaffrey, D. F. and Ritz, B. R. (1996) Groundwater Recharge with Reclaimed Water: An Epidemiologic Assessment in Los Angeles County, 1987-1991., Santa Monica, CA.

Sloss, E. M., McCaffrey, D. F., Fricker, R. D., Geschwind, S. A. and Ritz, B. R. (1999) Groundwater Recharge with Reclaimed Water: Birth Outcomes in Los Angeles County, 1982-1993. Rand Corporation.

Stuart Khan said...

Another major industrial user in Brisbane...

Govt denies it acted too slowly on recycled water
ABC News Online
May 22, 2007

The Queensland Government says it has moved as quickly as possible to get major industries to use recycled water.

The Government will spend $12 million to upgrade a wastewater plant at Wynnum, with the supplies to be used by the Caltex refinery - Brisbane's second largest water user.

It will save four-and-a-half megalitres of drinking supplies a day from the Wivenhoe dam.

The Opposition says it should have happened years ago but Premier Peter Beattie says it was the council that was acting slowly.

"I believe we've done this as quickly as possible," he said.

"As you know we haven't controlled water until recently - it's only been the drought that's enabled us as a State Government to take greater responsibility for water.

"You can imagine we're now trying to amalgamate council boundaries - just imagine what would have happened if we'd have tried to have a greater role in water - you'd have had the same argument."

But the State Opposition says major industries should have been using recycled water years ago.

Opposition Leader Jeff Seeney says it should have happened well before now.

"It's too little too late now - it should have been done years ago," he said.

"Had recycled water been used in those major plants for a period of time, there'd be a lot more fresh water left in Wivenhoe Dam now."

Anonymous said...

Hello Stuart,

I hope you are feeling better today.

Stuart Khan said...

thanks! :-)

AJ said...

Enough is enough. I respect contributions to public debate but this debate has become a soap box for Prof Collignon. How much more air time are we going to give to this guy because of his impressive credentials, which he has admitted are not applicable to this field? Seriously, he is obviously taking information and presenting it out of context. It's a bit of a worry that a Prof of infectious diseases is over simplifying the application of the Risk Matrix.
Deep breath...Stuart admire your factual responses to the issues he raises.

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