From design to delivery of Sewage Treatment Plant components to a site, through assembly, construction and then testing, start-up, operator training and final testing until all systems are “go”, is a rigorous engineering process that must be completed faithfully through to the end of proof of performance testing.
This is called “commissioning” – bringing something has been newly made into working order. The whole design, construction, installation, commissioning, start-up and testing process can take 5-6 months or even longer depending on the complexity of the treatment plant, but having it done properly is essential for the reliable future operation of a plant.
A plant that is well designed, built, commissioned and well-maintained can be expected to give 25+ years good, reliable service. At a cost that can be many millions for even a small plant serving a community of only a few hundred people, this is a significant infrastructure investment and one worth protecting. Not getting it right can halve the lifetime of a treatment plant.
If you divide the up-front investment by cost per year of ownership, it is very easy to see the business case for protecting that investment.
The provision of good, clean water and well managed water, wastewater and sewage treatment services to even the most remote community location is an essential requirement for basic quality of life. Getting it that way isn’t a simple process!
A project team is usually involved in the commissioning of a plant. This includes construction firms, process design engineers, water and wastewater specialists, OEM equipment suppliers and their representatives.
Breaking down the commissioning project – what steps are involved?
This commissioning process is responsible for the integrated application of a set of engineering techniques and procedures to check, inspect and test every component of a water treatment plant.
Everything is checked from the functionality of individual instruments to whole systems, covering all activities from construction, assembly, processes to the final handover of a plant to a fully trained or qualified operations team.
Factory Acceptance Testing (FAT)
The process begins with checking that all equipment shipped from the factory is working as expected and no damage has occurred enroute, and that all the mechanical equipment together is a working system.
Site Acceptance Testing (SAT)
Then comes wet testing: pipe flushing, leak and pressure testing, rotational testing of shafts and bearings, airflows, heating and cooling functions, extensive electrical testing, etc. Extensive testing is carried out on every component, and then, the whole system.
Once successfully commissioned, the plant can be turned ‘live’ and receive sewage. When this occurs, great care needs to be taken as it is a finely tuned process.
Settings need to be optimized to support biomass or sludge growth, which will need to be adapted over the start-up process as the population grows.
If you’re near a town you might be able to seed the process from donor sludge taken from an operational plant. If not, you need to grow your own biomass, which is a process that can take several weeks and needs careful attention. If you don’t get the plant started right, future operations will be difficult at best, with the potential for the plant to fail.
Proof of performance testing (PoPT)
Proof of performance testing involves rigorous testing for the new treatment plant and is conducted after everyone is confident that the plant is operating well and is hitting it’s targets. This can be anywhere from a 2 week test, with tests every day, to 4 weeks with test every few days, to 12 weeks or even longer. It all depends on the client but 2-4 weeks is a typical timeframe.
Start-up and PoPT also provide opportunity for the commissioning engineer to help train up the local operators, through a transfer of knowledge and skills that will be invaluable in future operation of the plant.
While rigorous commissioning and testing sets the plant up to excel, good operators are needed to keep it going.
The whole job from design to commissioning a new plant can take 18-24 months, depending on the complexity of the plant. Whilst good design and planning and the ability to carry out rigorous processes to the letter is critical, all this needs to be balanced with weather, equipment reliability, internal politics and skills, and the location of the plant.
Challenges for remote locations
Remote plants, like those located on remote islands can suffer delays due to shipping, simple logistics errors or even just poor timing on deliveries. The time it can take to bring new equipment in the case of failure, or extra assistance in the case of natural events that might occur during the commissioning process can be significant, and good planning will help minimize the impact of any issues that may be faced.
The importance of a good commissioning plan
A detailed commissioning plan should be created to methodically check every piece of equipment, instrument, control and interlock. Knowing you have the right plan, and following it, significantly reduces the potential of future problems, because you can be confident that your equipment works the way it is supposed to work (i.e. as per the Functional Description).
A recent case study
Most recently, Simmonds & Bristow delivered design, commissioning, and proof of performance testing for a new $9m sewage treatment plant manufacturer to a remote tropical community of 300-400 people.
The plant “went live” in November 2021 and the team are currently finishing proof of performance testing after several months of tuning, commissioning, optimization and testing. While good planning and commissioning have helped make the process reasonably painless, heavy rain posed a challenge to the project. The treatment plant coped well due to the fact that it had been well designed and constructed.
The plant has been designed for 400 people, or a flow of about 137,000 L/day, year-round. Flows varied at start up and were quite high initially, although much of the extra flow appears to have been caused by seawater ingress through pump-station over-flows. These were repaired by the local council operators, which helped significantly with excess flow. Flows, without rain, have generally stabilized at around 100,000 L/day, providing some capacity for growth in the community.
(Image: Design, troubleshooting and maintenance of remote area water and wastewater treatment plants is Simmonds & Bristow’s specialty).
The new plant replaced the previous treatment plant which had started to fail earlier than expected due to poor operational management over its lifetime. In a remote area like this it is hard to maintain continuity of skill and experience in the operating staff, who tend to come and go. A plant like this could last 25 years or more if the equipment is maintained correctly throughout its life. However without continuity of good operations, the lifespan of a plant can be as short as 10 years (or however long it takes a bearing to seize). Engaging a turnkey operations and maintenance arrangement with water management professionals would have gone a long way to assist in extending the usefulness of the plant.
The importance of live startup
Many OEMs (whose primary concern is equipment function) can install a plant like this, turn it on and walk away. Sadly, commissioning is not always done properly, or if commissioning is done correctly, often start-up (biological testing and optimization) is not. Plants may simply be turned on to their full capacity without consideration of how the biomass should be ramped up or grown. This specialized knowledge is not always part of an OEM’s skillset.
Biological commissioning, start-up and operator training are where Simmonds & Bristow can really add value. We can act as a subcontractor to an OEM, or a representative of the client themselves – not just in ensuring the commissioning and proof of performance testing is done properly (including biological testing) but in offering maintenance oversight, support and continuity of operations intelligence through the life of a plant.
This will ensure the life of the plant can better reflect the (usually) very high initial investment.
Process Engineer at Simmonds & Bristow