Reliance on instrumentation can only increase
David Claridge, manager of Endress + Hauser's water division, looks at the future of instrumentation following major staff cuts by UK water companies.
The basis for the above statement includes a wide variety of often conflicting requirements, imposed by a similarly large range of interested parties. Amongst the highest-ranking requirements are those of Ofwat, the EA and EC directorate. As a minimum expectation under AMP3, Ofwat have four main requirements that, to a degree, encapsulate the views of other parties. The four are:
- No deterioration in services to customers or the environment
- Improve drinking water quality
- Deliver on time the largest ever five-year environmental improvement programme
- Maintain asset serviceability in the interests of customers
In addition, more data is being requested for by various parties to substantiate water company claims and to satisfy the regulatory bodies that targets, both legal and environmental, are being met. The AMP3 programme includes the largest ever five-year environmental programme. The main emphasis is on the improvement of discharges from STWs and CSOs.
These increased requirements and environmental regulations must be met under increasingly difficult conditions. Financial and regulatory constraints are increasing, along with shareholder expectations. This led many water companies to shed more staff following Ofwat's price cuts in November 1999.
The reduction in manpower will have a major impact on the operational maintenance of all assets owned by the water companies. Personnel who would normally operate or maintain a site will no longer be available to ensure the smooth running of or quick repairs to existing equipment, which has often exceeded its planned asset life.
Equipment is often required to perform for longer than originally intended. As a consequence, more information is needed on a treatment plant and the state of incoming flows, either raw water in WTWs or effluent in STWs. The only realistic way to obtain this data, in a useable manner and timescale for controlling responses to changes, is to use online instrumentation. As manpower decreases, the planning of maintenance becomes critical. Ideally, the amount of corrective maintenance should be reduced, and the amount of predictive maintenance increased. This can be achieved by obtaining information on the current and predicted state of equipment by using self-diagnostics.
Elements of preventive maintenance, including areas such as cleaning, could also be reduced by the introduction of self-cleaning equipment. However, care must be taken to ensure such maintenance has a beneficial effect because tampering with an instrument can often reduce its accuracy.
Manufacturers can help by providing systems with self-diagnostics and maintenance-reducing options and by offering assistance in specifying and installing equipment.
An increasing reliance on instrumentation can be seen from companies who supply packaged processes such as sequential batch reactors (SBRs). Significant improvements with aeration tanks have been achieved by finer control of flows and aeration rates. In order to achieve this level of control an increased number of dissolved oxygen (DO) meters have been installed or, in some cases redox equipment for increased rangeability. Accurate DO profiling and an improved understanding of the treatment process has resulted in:
- Increased asset capacity
- Improved effluent quality
- Energy savings due to reductions in demand for DO
- Increased flexibility, allowing for effluent quality and ambient condition fluctuations (e.g better control of nitrification/de-nitrification changes)
Providers of SBRs are relying on flow, temperature, pressure and analytical measurements to optimise batch control and increase throughput of the final treated effluent.
Crisis of confidence
However, in some areas of the industry, there appears to be a lack of confidence in instruments and the data produced by them. In some cases, these fears are justified, but incorrect data is often produced due to poor maintenance, poor installation conditions, incorrectly programmed instruments, or because the cheapest available instrument has been chosen.
As asset design standards and process standards increase, the instrumentation specification will increase and the number of instruments required to obtain these standards will also increase. Whole life costing is now being considered to a greater degree by many water companies, but this is causing conflicts between controllers of CAPEX and OPEX.
Historically, initial purchase price has been the driving factor in the choice of instruments on new projects. However, reduced impact on CAPEX will be outweighed by increased expenditure on OPEX if unsuitable instruments are supplied.
Here too manufacturers can assist by providing information on spares costs and added value packages, which can be used to predict appropriate maintenance intervals in relation to performance requirements.