Demand Management series by Dr Ronnie McKenzie – Part 1 of 4: Prioritizing Demand Reduction

ROCKBlue recently had the privilege to interview Dr Ronnie McKenzie from WRP Consulting Engineers and got his expert insight on a few Demand Management topics. We are sharing these in a series of four blogs starting with Prioritizing Demand Reduction.

Dr McKenzie is a world-renowned expert in demand management. He’s also the Managing Director at WRP Consulting Engineers in South Africa which specializes in water loss management. He has been involved in the analysis of water systems throughout the world.  He introduced the Burst and Background Estimate methodology to South Africa as well as the principles of advanced pressure control.

He has developed packages to assist water utilities manage their leakage including: SANFLOW, PRESMAC, BENCHLEAK, ECONOLEAK, and Aqualibre.

He was responsible for the initiation and development of the Khayelitsha and Sebokeng pressure management projects and provides specialist support to various international organizations including the United Nations, European Union and the World Bank Institute.

Dr McKenzie is the Chair of the International Water Association (IWA) Specialist Group on Water Loss and a Fellow of the IWA and the South African Institute of Civil Engineering. He received the inaugural Ministerial Award for services to South Africa in the field of water demand management.

Part 1: PRIORITIZING DEMAND REDUCTION

How does a utility or a municipality, struggling to keep a positive cash flow, justify spending money on demand management, thus reducing the customer payments associated with volumetric use?

A “demand” reduction can also be considered equivalent to a “supply”. In this regard, it is probably your cheapest resource if you compare it to traditional resource developments like dams and new pipelines, etc. Overall system “demands” also include water that is lost or unaccounted for (a.k.a., non-revenue water or NRW).   Reducing water demands may also help to avoid the need to develop new treatment works and upgrading of water mains etc., and so even in a municipal environment, reducing demands through water loss reduction can yield massive benefits.  Typically, in developing countries, your NRW is up around 30 to 60 percent. And that gives you a huge potential resource that you can tackle.

In most cases, the benefits of demand management are clear cut from the point of view that there will always be components of the water balance which are not being paid for (e.g., NRW). And, if a municipality can identify where they’re losing water – that is water not being paid for – they should tackle that as the first priority since the “pay-back” will often be very attractive. This doesn’t necessarily mean reducing their customer income. In some cases, it will result in customer income dropping, but in most cases, the municipality will be able to reduce their water demands without reducing net customer income. So, the trick is to tackle the areas of water wastage where the water is not being paid for as first priority.

If a utility or a municipality wants to significantly reduce industrial commercial demands should they work directly with their consumers to reduce demand? Or is it more cost effective to engage the private sector who engage those consumers?

In my view, large industrial consumers, should be the last customers that a water utility really tries to cut the demand. In many cases industrial water users are a major contributor to the overall income of most municipalities and will generally pay their water accounts in full and on time.  Cutting down the water use on the industrial consumers may potentially bankrupt the utility and so they should be treated carefully.  I would always recommend that water meters to all large industrial consumers be checked regularly and perhaps even monitored continually using some form of logging so that the accounts are accurate.  Large bulk meters should always be checked every few years for accuracy as even a small inaccuracy (usually under-recording) can result in a significant loss of income to the municipality.

If the industrial customer is not wasting water and is paying for the water it uses, the water utility should look after this blue-chip customer. The water utility must not damage its business model by cutting down the water use of large customers that are paying for the water.

A responsible water utility will always try to assist its top customers in reducing their water use in cases where it is found that there may be a high level of wastage or leakage. Reducing industrial water use is not always simple or quick to implement since some industries have developed processes or use specific equipment as part of the manufacturing process. Changing the industrial processes to a more efficient process can be prohibitively expensive and may not be feasible such as changing the water consumption in a car paint shop for example.

Can you speak the situation that a lot of utilities face with intermittent supply, where the pipes are not always pressurized? This results in large pressures on valves and often of dirt and debris infiltrating into the network. How can you protect your valves under those very real conditions for many municipalities?

If you’re providing intermittent supply, then you’re in a different case all together. Intermittent supply is a specialized area on its own. It’s the last thing that you should do, and it puts you on a downward spiral. You’re destroying your network by putting air into the system, which must find its way out. Invariably, if you don’t have enough water to keep your system going, the chances are that the air valves wouldn’t be working either. So, you’ll be pushing air in and out of the system, regularly blowing up your pipelines. Eventually you’ll be destroying your whole network and you’ll invariably have to replace the complete network, which is the most expensive thing you can do. Intermittent supply is never viable, never a good thing.

It is much better to operate a system on a very low pressure continually than try and have an intermittent supply. For example, many utilities have a firefighting requirement of 25 meters of water pressure (a.k.a., “head”) – so the system’s designed for 25 meters of pressure. And some utilities would rather provide intermittent supply than operate the system at say five meters of pressure. In my view, operating a system at five meters of pressure continually is far better than operating at 25 metres of pressure for twelve hours a day and then twelve hours off.  No-matter what a water manager says to motivate intermittent supply – it is never the best option and a continuous supply at a very low pressure will often use LESS water than an intermittent supply which switches between high pressure and no pressure daily.