Turning wastewater into an economic resource

In a difficult environment for manufacturers, cost management has become a leading indicator for ensuring a viable future. A growing area in the effort to contain costs at manufacturing facilities focuses on the economic optimisation of wastewater treatment. pitt&sherry Principal Consultant Dr Steve Edwards has worked with manufacturers from a variety of sectors to help them achieve optimum results.

Dr Steve Edwards.

Economic optimisation of wastewater treatment is vitally important for Australian manufacturing and processing facilities aiming to curtail costs, according to Dr Edwards, who says manufacturers can optimise their economic choices when treating and recycling wastewater by investigating a variety of options.

“What we traditionally regard as wastewater can be a misleading concept, as wastewater is in fact a resource that must be accounted for in terms of its energy output if nothing else, so sometimes there is an upside,” Dr Edwards said.

“Manufacturers need to identify where they can reduce wastewater discharge and how the remaining resource might then be re-used in an economic and sustainable manner. More often than not the best economic outcomes can also the best for the environment.”

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

Capital spend

According to Dr Edwards, the big question for manufacturers is how 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.

It was found that the dairy manufacturer had several technology options. 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.

“Does the company heavily focus on spending its budget on stage one? Or is it more economical to spread the capital evenly over three stages?” Dr Edwards said.

“This was a key economic question posed to the dairy manufacturer on this development. 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 the 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,” said Dr Edwards.

“For this work, elements like peak flows and concentration of wastewater were analysed and included in recommendations to the client. Someone needs to sort through the claims and confirm what works and what impact each option has on life-cycle cost.”

In this case, analysis was provided 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 has a 24-hour cycle which produces small amounts of wastewater during the day then peaks at night.

“Depending on the costs involved, a facility might look at the risks and say ‘if a tank bursts we’ve contained the spill on the other side from the water authority and from an environmental perspective’,” Dr Edwards said.

“This still raises 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, pitt&sherry designed a system with surges and flows that allowed for the wastewater to be contained in the factory for a short while when spilled, 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,” said Dr Edwards.

Mining scenario

pitt&sherry has advised one of Tasmania’s largest energy users of its options to economically optimise how wastewater is treated at its mining operation. For this client, studies into chemical use, how much chemical was being used and what kind of pipeline would suit the operation were undertaken.

“This 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,” said Dr Edwards. “And if new equipment was integrated, what are the economic implications of the new system for the rest of the process?”

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 80 km pipeline to obtain fresh water from the local authority.

“The principles don’t change despite the change of industry,” Dr Edwards said. “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 pay back in reduced disposal charges, compared to the cost of the equipment and the process.”

Dr Steve Edwards is a scientist with a background in organic and natural products chemistry and aquaculture.Since joining pitt&sherry in 2007, he has gained extensive experience in process optimisation and process modelling, with a particular focus on carbon accounting (LCA) and energy and water efficiency.