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- MWH and 4D lead with real-time control project in UK

A new advanced control system for wastewater treatment plants is being introduced at six of Southern Water’s treatment plants in the Chichester area. This is one of the first applications of real-time control in the UK. It is the result of MWH and its joint venture organisation, 4 Delivery (4D), collaborating with Southern Water to meet its AMP 4 wastewater standards. This will minimise capital expenditure, maximise performance and lead to carbon emission reductions of around 25% equivalent to taking 600 cars off the road.

Ajay Nair, MWH Principal Process Engineer seconded to the 4D JV explains, “Under traditional control systems, it is not possible to make use of the safety factors built into a treatment works to take account of the wastewater variability and seasonal changes. By controlling a treatment plant to match the actual conditions experienced at that time, rather than an “average” or minimum condition, optimum treatment and energy consumption can be provided. The term “real time” control has been used to describe this particular method of aeration control.”

For AMP4, Southern Water was challenged with providing Total Nitrogen Removal at six of their treatment plants (Budds Farm, Peel Common, Chichester, Sidlesham, Thornham and Bosham). The first three plants already use energy intensive activated sludge processes. If these processes had been combined with total nitrogen removal without ‘real time control’ it would have resulted in at least a doubling of energy use plus significant additional carbon emissions due to the need for methanol dosing.

Therefore, to minimise the negative impacts on the environment and the company and to ensure it met the new regulatory compliance requirements, Southern Water and 4D have worked towards reducing the carbon footprint associated with each of these new plants by using real-time control. These will be amongst the first systems of this kind to use real time control in the UK, demonstrating Southern Water’s and 4D’s commitment to carbon savings and bringing innovation into the UK market.

David Craft, Principal Process Engineer of Southern Water explains; “Currently treated wastewater standards are dictated by the short to medium term impact on the receiving water body. Until recently, no consideration was taken of the carbon impact of the more energy intensive processes needed to meet tighter standards – creating a regulatory vicious circle. However, it would have been irresponsible not to have chosen this innovative method as the increase in carbon emissions associated with the treatment plants to meet the new standards at Chichester, Peel Common and Budds Farm would have otherwise been the equivalent of 2,500 extra cars on the road.”

He adds that in addition to significant carbon reduction through the use of real time control, an improvement in compliance is also achieved at the same time as reducing operational costs, as the plant reacts instantly to changes in the influent and constantly operates under a very stable condition.

By implementing the control systems, it is anticipated that carbon emission savings that can be achieved on all three of the schemes will be around 25% (equivalent to 600 less cars). In addition to carbon reduction the cost benefit associated with the energy and methanol savings is also significant, providing additional financial incentives to install real time control systems. Currently, the partnership has selected a preferred supplier and a preferred method of the advanced control system to minimise capital expenditure and maximise performance. However, Nair is keen to stress that although, financial drivers are still very relevant, the sense of urgency around climate change is such that a greater emphasis is being placed upon carbon reduction techniques as the primary filter.

Narinder Sunner, MWH Principal Process Engineer leading this initiative says; “Both Southern Water and 4D have demonstrated their commitment to pioneering technologies that actively reduce carbon emissions to meet the compliance standards applied. The work conducted to date sets the foundations for future energy reduction strategies not only for Southern Water, but for all UK water utilities if our national target of a 26 - 32% reduction in CO2 by 2020 is to be realistically achieved.”


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Editors Note:

4D and Southern Water have collaborated to help meet some of the challenges faced in introducing real time control processes. These have included –

· Fact finding missions to the US and Germany, where the technology has been used;

· Discussions with experienced designers across the globe on success or issues

· A series of intensive instruments trials at Southern Water sites to prove
effectiveness and selection of the best instruments;

· Development of a programme of installation which does impact on over plant

· Development of testing methods allowing direct comparisons of carbon and cost
savings made;

· Intensive discussions with the two suppliers to overcome issues of instrument
compatibility and support during the set-up phases.

The major benefits provided by the real time control system are:

· Rather than using oxygen concentration as the main control, ammonia is used to
predict the amount of air needed so the system reacts quicker.

· By using ammonia as a direct measure, over-treating and wasting energy is

· The internal re-cycles can be optimised so only what is needed is pumped rather
than over-pump.

· Seasonal conditions can be matched to take advantage of the faster reactions
that occur in summer time reducing the energy wasted which would be used simply
to treat by-products.

· The amount of methanol used by optimising the 2nd stage removal and reducing
the impact of dissolved oxygen on consumption.

Activated sludge plants require oxygen for the various organisms involved to convert the incoming wastewater to a less reactive form. Oxygen is supplied by bubbling air into the reactor using blowers and diffusers. The amount of energy used in directly related to the amount of air supplied, so it is vital to make this part of the process as efficient as possible.

Traditionally, the amount of air supplied has been controlled using a direct measure of the oxygen concentration at different points in the reactor. Whilst this has been successful, the limitations associated with this method are numerous, so any additional improvements in energy reduction are limited.

For example, there are periods of time when the oxygen demand is so low that the liquid oxygen levels increase above the desired value and cannot be reduced as the minimum airflow to maintain mixing is reached. Effectively energy is being wasted down the outfall.

About 4D 4 Delivery

4 Delivery (4D) is a Joint Venture company between Costain, United Utilities and MWH, established to deliver over £700 million of Southern Waters’ 4th Capital Maintenance Programme between 2005 and 2010.

The 4D programme is a multi-project design and construct programme where MWH are predominately responsible for providing the engineering functions for the JV.

About MWH

MWH is a private, employee-owned firm with approximately 6,000 employees worldwide. The company provides water, wastewater, energy, natural resource, program management, consulting and construction services to industrial, municipal, utility and government clients in Europe, the Americas, Middle East, India, Asia and the Pacific Rim. MWH has worked in the UK for over 160 years and has designed, built and managed many of the largest, most innovative and technologically advanced projects around the world. For more information please email or visit

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