Capital expense (CapEX) purchases in the headworks or any other part of the wastewater treatment plant (WWTP) are significant investments. The right investment can resolve major issues and help ensure the plant is running smoothly for decades to come. However, a poor choice can result in downtime, operational issues, and more. As such, this is not a decision any plant manager or design engineer should approach lightly. Operators may have had good experiences with a particular brand in the past, but that does not guarantee the vendor will be the right choice for every application. Knowing what questions to ask about the plant, the technology, and the vendor is critical to making the best possible investment with the best possible outcome.
Understanding Your Specific Needs
Before looking at specific equipment, plant managers must gather essential data about their own process and site specifications. Primary among them is the budget, followed by process requirements. For example, a moving bed biofilm reactor (MBBR) has different screening and possibly secondary screening needs than a membrane bioreactor (MBR) or sequencing batch reactor (SBR).
Flow rates are the next most critical piece of information. Generally, equipment selection should be based on the peak hourly flow. However, it’s also important to understand the minimum flow and the average daily flows, as this will dictate the necessary turndown ratio. Similarly, the design should consider the frequency and intensity of storm events.
Footprint also needs to be factored in. For example, a facility that is rated for 100 MGD can have one influent channel or 10 separate 10 MGD channels. Both are viable options but will demand very different footprints, budgets, and technologies. Topography also matters. If the influent channel is very deep, it can limit the project to the types of technologies that can reach those depths.
Lastly, project managers must balance future needs against today’s budget. The equipment choice can include potential capacity needs in 20 years, but this can cost more up front. In some cases, it may be more economical to design with the intent of further expansion.
Matching Technology To Applications
Certain applications may dictate which technology can be used. For example, in a large headworks, grinders are used mainly to avoid clogging in transfer pumps, which means coarse grinding is usually sufficient. Dual shaft grinders are predominantly used in industrial applications where high torque is required, while most municipal applications only need a single shaft grinder.
Similarly, a lagoon may need little or no screening, while an MBR or MBBR may need to screen down to 2 mm, which could necessitate secondary screening. Of course, the current capture rate efficiency should also be taken into account, as it’s common for operations to become less tolerant of debris over time. As such, regardless of the level of screening or grinding being performed, plant managers may want to step it up to the next most cost-effective level.
Total Cost Of Ownership (TCO)
TCO is often the core basis of an evaluated bid. With the exception of pumps, most headworks systems already consume comparatively minimal electricity. However, many screens and other systems use water for cleaning. If a screen runs 4 or 5 hours a day, the cost of using 100 gallons of water per minute adds up.
Maintenance is another key factor in TCO. For example, drum screens have few seals that need to be maintained, while perforated plate screens have many seals that need to be replaced frequently. Similarly, vertical bar screens or flexible rake screens are popular because they require little maintenance or other operator intervention.
The Importance Of Service And Support
When assessing vendors, nearly all WWTPs need local support teams. The local representative should be evaluated along with the manufacturer. Are they in the business of servicing equipment? In addition, does the manufacturer stand behind their equipment with a large and capable field service team?
It’s also worth considering whether the vendor offers preventative maintenance contracts. While equipment like grinders are often run-to-fail, the WWTP can save significant money over the long run by performing scheduled maintenance once or twice a year as needed.
Last, and most importantly, is integrity. Engineers and project managers must work with a vendor that wants to sell the most appropriate solution, even if it means reducing the price of the sale or recommending a competing brand.
Investing in new headworks equipment is far more than a simple purchase — it’s a long-term decision that shapes plant performance, reliability, and operational costs for years to come. By thoroughly understanding site-specific needs, matching technologies to the application, and evaluating vendors based on support, service, and integrity, utilities can make informed choices that truly pay off. A careful, data-driven approach ensures that the selected equipment not only meets today’s demands but also positions the facility for future success.