Model behaviour

The development of software to monitor and control the treatment of industrial effluent is one area that has attracted considerable interest in recent years. Indeed, the use of software solutions in planning all types of industrial development from concept to completion is now widely accepted. Modelling the options before beginning development enables companies to examine the widest range of alternatives and solutions at least cost.

Modelling can be applied to almost every aspect of industrial operations, whether the goal is to minimise use of resources, introduce new processes or expand existing facilities. In addition, so-called 'intelligent equipment', incorporating embedded software, is set to make a significant contribution to improved control and monitoring of production in many sectors of industry.

A sizable proportion of these costs has necessarily been passed on to customers. Many companies are struggling to reduce the impact of these increased water charges and comply with effluent discharge limits imposed under the Local Authority Pollution Control regime.

A new mantra is emerging for companies wishing to cushion the impact of these increased charges: 'reduce water consumption, optimise processes, and minimise effluent generation'. It applies to most industry sectors, but particularly to those, such as the dairy, brewing, pharmaceutical and metals industries, that use large quantities of water - and hence generate potentially large amounts of effluent.

For example, many breweries discharge, as effluent, up to 70 per cent of the water that is supplied to their sites. Advice on saving water and reducing effluent is available from the water utilities and government agencies, such as Envirowise, but there is also a growing band of consultants offering software solutions that can help optimise processes and minimise effluent arisings.

The international water and environment consultancy, WRc, has developed a range of practical, cost-effective solutions for water, wastewater and industrial effluent treatment challenges. Software solutions are available for odour management, risk and reliability modelling, and water and wastewater treatment processes.

Model roles
Packages such as Polecat and Plan-It-STOAT (Plan-It) can help companies improve their waste treatment processes, reducing water consumption and effluent generation, thereby making worthwhile savings on water charges. Both Polecat and Plan-It are Windows-based modelling tools with wide ranging applications.

Polecat has been used successfully to model the effluent from fermenters and waste tanks at a brewery site in the North-East of England. The model can estimate waste arising in terms of a range of parameters, such as flow and chemical oxygen demand (COD). This enables the user to assess the possibility of re-using wastewater in applications where mains quality is not essential. It can be used to schedule tank cleaning and reduce water consumption, thereby optimising cleaning cycles to reduce peak flow and improve operational efficiency. At one brewery it has even been used to modify wastewater treatment, resulting in reduced discharge costs.

Plan-It-STOAT was also conceived as a tool for modelling the load and flow of waste arisings from industrial processes. It can be used in any industrial application where the waste is biodegradable, though it was initially proven in sewage treatment. The package has a detailed hydraulic capability allowing it to even out loads - in this instance the flow rate and biological oxygen demand (BOD) - of the effluent. 'Smoothing out' the flow in this way brings the maximum flow rate closer to the average flow, achieving a steadier flow rate and avoiding large surges that can overload the treatment plant.

Turn the tide
This 'smoothing' capability means that, in the event of needing to expand the plant, the scale of expansion can be optimised to accommodate actual need, rather than building in unnecessary overcapacity. Plan-It can determine the point at which increasing the load would exceed the capacity of the plant's pipe systems to transport effluent, and when the whole plant would reach overload, and can also be used to demonstrate the relative investment benefits of, for example, activated sludge versus anaerobic
treatment methods.

Many leading industrial companies are already reaping the benefits of using software to solve the challenges of industrial effluent treatment. Others will inevitably follow their example in a bid to turn back the rising tide of higher charges for water and wastewater services.


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