Put that cheque book away

Looking after equipment you already have in your treatment plant is a way of keeping up efficiency levels to meet industry standards. Chris Day argues that effective asset management is a better strategy than splashing the cash on new gear.

AS AMP5 appears on the horizon, industry soothsayers predict this spending round will emphasise the need to maximise effectiveness of existing plant rather than making new investments.

The industry should not lose sight of the fact that Asset Management Plan is what the AMP rounds are all about.

Volatile oil and steel prices, and the growing pressure to reduce carbon footprint all put a sensible emphasis on maintaining and optimising the equipment before getting the cheque book out. While new treatment plant will inevitably be required to deal with ever-increasing volumes of effluent flow, at least some of this could be treated by bringing existing plant back up to efficiency.

Already investing

In fact, a survey of plant efficiency might reveal surprises as to how far it has deteriorated.

This does not mean utilities are not already investing in their assets. Northumbrian Water reportedly spent £185M in 2007/2008, and United Utilities has been reported to be spending £2.3B over AMP4. But one area for concern is the effective operation of the asset management team.

Setting up dedicated asset management teams is the start of the process. Ensuring it has an effective operating structure, standard procedures, and reporting from the outset is essential. Expecting team members to adapt to a way of working that is foreign to their original management training is perhaps naive.

A primary question that should be asked of those managing a utility’s assets is: “Why has effective original plant been allowed to run down?” The answer may well be a combination of several factors, including the built-in effectiveness of equipment designed for long life.

Also, the industry has focused on Capex for acquiring the latest technology to meet increased quality and quantity standards, and perhaps been reluctant to allocate adequate resources to asset maintenance.

If the new emphasis on asset value maintenance means treatment plant operators look at whole life costs, then they may well obtain better value for their expenditure.

A difference exists between equipment with predominantly mechanical functions where systems have a defined life due to wear, and plant working on induced movement where the medium – such as water – is the only moving part.

Mechanical equipment with many moving parts includes screens with mechanical scrapers, aerating fans, pumps and sludge dewatering plant. Plant designed to use vortex technology, gravity feeds and settlement is not so vulnerable to wear and damage.

Mechanically reliant systems have the habit of breaking down altogether due to component failure, while plant not mechanically dependent is generally more able to limp along.

Reliant systems

Operating heavily mechanically reliant systems also requires significant energy input. The reduction in energy consumption – largely electricity – also means a plant’s carbon footprint is minimised.

With favourable topography, use of hydrodynamic vortex flow designs of screening and separation plant enables high- performance operation at minimal energy consumption, and with few moving parts.

Typical of these is Hydro’s Grit King, which separates, cleans and dewaters grit from incoming raw sewage and other liquids prior to delivering the grit to a skip. The Grit King Separator uses the inherent energy of the influent. A recent example of an upgraded existing asset was a vertical sand filtration plant used for final effluent polishing prior to discharge. Influent water circulates up through this plant, and a small amount of compressed air is injected at the bottom to lift filter sand to the sand washer; there are no mechanical moving parts within the plant.

The installation had not been maintained for ten years, over which time the quality of the final output had deteriorated to a point where remedial action was mandatory following Environment Agency monitoring. Investigation by Hydro wastewater technicians found that the sand had been badly contaminated.

The plant was restored to full working order by completely removing the original filter sand, cleaning the vessels and refilling with new filter media. But this necessitated shutting down the filtration plant and replacing some of the internal pipework. The cost of the refurbishment was about £190,000, in contrast with an annual maintenance contract of £5,496 for bi-monthly visits.

The cost comparison over ten years is that an annual maintenance contract or even an occasional routine service by the equipment manufacturer could have greatly reduced the cost by a factor of three.

With a process operated by mechanical equipment, the replacement of parts such as seals, filters, lubricating oils, rotors/stators, and bearings is more pressing. The costs of consumables such as these are easy to identify against defined time lines.

But some engineers may be tempted to ignore the predicted time lines, and assume that these timings are conservative, so that the user can take them with a pinch of salt. In the past in old-fashioned boilerplate engineering, there was almost always a built-in safety factor. Nowadays, with cost efficiency and lean/value engineering, the design life of components is pared to the stated value.

Taking what may seem like a small risk with a relatively inexpensive component to postpone a maintenance bill until the next accounting period may in retrospect become an unwise decision.

Plant safety

When applying the discipline of risk management, you acknowledge that nothing is perfect and, with a number of variables, anything could go wrong. This approach takes a view of failure on the basis of probabilities and the cost of the consequences. Risk management facilitates a logical appraisal, and helps map out the decisions that should be made. Many engineers will be familiar with it through plant safety assessment procedures.

A similar approach to plant maintenance indicates that planned maintenance and condition monitoring will be the low-risk strategy. Investing in a proper maintenance service, backed up by a spares portfolio, will cost less than plant downtime and emergency plant refurbishment.

So a key to efficient use of AMP5 funding could well be looking at risk management in wastewater treatment plant, and using it as a basis for properly planned maintenance. Having these plans in place when the funding is allocated will show the importance you attach to plant efficiency, and how you could spend the allocation wisely.

Chris Day is director of Hydro International’s Wastewater Division

T: 01353 645700

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