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Why manufacturers need to focus on economic optimisation of wastewater treatment

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article image Dr Steve Edwards

Pitt & Sherry Principal Consultant Dr Steve Edwards works with manufacturers from diverse industrial sectors to help them achieve optimum results in wastewater treatment.

Manufacturers are focusing on economic optimisation of wastewater treatment to contain costs at their facilities. According to Dr Edwards, economic optimisation of wastewater treatment is vitally important for Australian manufacturing and processing facilities aiming to curtail costs. 

A wastewater treatment plant may form part of a greenfields project, be an element of a facility upgrade to improve efficiencies, or part of meeting the rigorous standards water authorities have applied to the area in recent years.

According to Dr Edwards, manufacturers can optimise their economic choices when treating and recycling wastewater by investigating a variety of options. He explains that the traditional concept of wastewater can be misleading because wastewater is actually a resource that must be accounted for in terms of its energy output. 

Dr Edwards says that manufacturers need to identify where they can reduce wastewater discharge and how the remaining resource might then be reused in an economic and sustainable manner. 

pitt&sherry has worked with companies in the dairy and mining industries by analysing the economic case for different wastewater treatment methods.

Capital spend

Manufacturers need to find the right balance on capital spent creating wastewater treatment assets before funds are paid to the local water authority for treatment.

For one dairy facility development, pitt&sherry looked at the contractual requirements to provide a perspective between sending wastewater to the local authority, and the required spend to treat the water to a higher condition on site.

Among the several technology options available to the dairy manufacturer, an approach that stood out was to move the waste through up to three stages of treatment for it to reach the required condition of the water authority. In this case the treat-on-site option was a better economic outcome. 

As part of this process the manufacturer also needed to decide how to spread its capital between these three stages. However, it can be difficult for the client to assess this question as there is a lot of information that needs to be processed.

Firstly, there are manufacturing claims, which are often based on industry averages and norms for a treatment type. The company must know whether the claims being made are realistic. It also needs to understand the implications of possible scenarios for its unique wastewater. It will also bring up issues with peak flows and average flows of wastewater, which can add costs to the client because of charges on a number of different areas.

For this work, elements such as peak flows and concentration of wastewater were analysed and included in recommendations to the client. Analysis was provided to the client showing a 15-year net present cost difference of up to $4 million between options.

Risk analysis

On another dairy project, pitt&sherry’s focus was more on the risks involved with the economic decisions the manufacturer had already applied to its wastewater treatment. The manufacturer was taken through a comprehensive hazard and operability study (HAZOP) for this purpose.

pitt&sherry worked through various risk scenarios by analysing what would happen if the Environment Protection Authority (EPA) raised these situations, as well as the potential costs involved in these instances.

A system capable of holding the water leaving the plant was designed, taking into account that the facility had a 24-hour cycle, which produced small amounts of wastewater during the day and then peaked at night. Even if the facility was able to contain the spill in the event of a tank burst, it would still raise questions from the water authority of what would be done with the contained waste after the spill. The client did not want these risks or the excess costs of building and maintaining complex holding and disposal systems. 

To accommodate this requirement, pitt&sherry designed a system with surges and flows that allowed for the wastewater to be contained in the factory for a short while during a spill, but then released once it reached the parameters of the wastewater authority.

The design allowed for additional tanks, which may not be used, but have been installed to take all of the extra water and have it properly treated by sensing the pH and pumping the water slowly back into the existing outlet mostly without additional chemical treatment cost. 

Mining scenario

pitt&sherry has advised one of Tasmania’s largest energy users of its options to economically optimise wastewater treatment at its mining operation. 

Studies into chemical use, quantity of chemical being used, and the kind of pipeline that would suit the operation were undertaken. Dr Edwards explained that the client wanted to optimise its capital investment, but at the same time was keen to investigate the possibility of moving to new wastewater treatment equipment. However, the economic implications of the new system for the rest of the process also needed to be considered. 

pitt&sherry established several options for the client, including guidelines for chemical and water use, and how they would impact capital expenditure. One option involved the design and construction of an 80km pipeline to obtain fresh water from the local authority.

Dr Edwards comments that the principles remain the same despite the change of industry; they are still the principles of sustainability: reduce use and recycle where possible. If these principles are applied to each unique situation the economic gain will follow. It’s just a matter of receiving payback in reduced disposal charges, compared to the cost of the equipment and the process.

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