• SC1000 Multi-Parameter Universal Controller: This advanced, solid-state, modular controller can manage up to eight sensors directly or be deployed in wired or wireless SCADA networks with up to 32 sensors and parameters. Its intuitive, easy-to-use interface and large colour touchscreen display that can be used for the monitoring and control of any number of parameters.
• PHOSPHAX SC Digital Phosphate Analyser: This orthophosphate solid-state analyser comes in a ruggedised weather-proof housing to provide continual, highly precise measurements of orthophosphate concentrations directly at the tank. Its detection limits can be set as low as 0.05 mg/L, with response times of less than five minutes including sample preparation. It consumes minimum reagent amounts. Output options include 4-20 mA output, Modbus RS485, Profibus, or HART. In the deployment at the Midwestern WWTP, it was set to measure plan effluent every five minutes
• Phosphorus Real-Time Controller: This solid-state controller responds to master commands from the SC1000 universal controller to manage in real time the flows and precise chemical discharge from the ferric chloride feed pumps into the effluent stream.
Proactive performance monitoring. Many WWTP operators strive to be self-sufficient in support of their own equipment. The simple design of this prepackaged solution using off-the-shelf components can enable them to do so. What’s more, operators have to trust that the technologies they deploy work as specified 24/7. That’s why the Hach’s full-line of RTC solutions for WWTPs (see sidebar) comes with the PROGNOSYS predictive diagnostic system. As a subsystem, the PROGNOSYS software continually monitors the overall
RTC system’s health and provides early warning alerts for any impending instrument performance issues. It helps WWTP operators be proactive in troubleshooting, maintenance, and repairs – before minor problems become major disruptions. It also gives them the confidence to know whether changes in measurements are due to changes in the system’s instruments or the wastewater stream. Make vs. Buy: The Allure (and Pitfalls) of In-House Solutions Many WWTP operators may opt for developing their own in-house RTC solutions for several reasons, all with the best intentions.
An obvious one is to save money by buying and assembling into a system either lowest-cost components (or even higher-cost, best-of-breed ones to get the latest and greatest features and performance). A custom solution might also be desired to accommodate a wider range of functionality than prepackaged solutions might offer. Next, to save more money on implementing the in-house solution, staff resources would do the logic and functional programming, then the installation and configuration. In addition to the cost-savings, other apparent benefits would include self-sufficiency and the avoidance of vendor lock-in and ongoing service and support costs.
When day-to-day gets in the way. Unfortunately practical day-to-day WWTP operating demands can cause less-welcome outcomes to the great expectations of the do-it-yourself game plan. For example, the in-house effort gets started but other priorities arise, causing its execution to become a series of fits and starts, or derailing it altogether. Or the project gets bogged down in programming issues. Either way, the RTC opportunity remains unaddressed. Alternatively, a customised, in-house RTC solution may get built, installed, and properly configured and work just fine, as long as the individual who designed and engineered it remains on staff. Without that person available when the system goes down – and lacking sufficient documentation, which is often the case – the WWTP is left to, in effect, reverse-engineer the system to fix it or call in a third-party service provider to figure it out. Meanwhile, the plant must go back to time-consuming and costly manual procedures until the system gets fixed to avoid regulatory fines and repetitional damage.
Advantages of prepackaged, turnkey RTC solutions. Because few WWTP operators can spare technical or engineering staff time to develop in-house solutions, the temptations to embark on such a project should be resisted. Or they should at least be weighed against the risks of unforeseen but time- and cost-consuming delays in design, engineering, installation and configuration due to interoperability issues among the components, software programming problems, or some combination of both.
Of course, WWTP operators might not have any alternative than in-house solutions, if not for the availability of prepackaged, turnkey RTC solutions made from proven off-the-shelf components, such as those from Hach. The advantages of this approach are many. One is faster time to system commissioning. While an in-house approach could take months or even years, the prepackaged, turnkey approach can take just weeks or even days, if a WWTP is in a hurry. In the Midwestern WWTP example, the phosphorus control system was installed, configured, and operational in less than 48 hours. Another big advantage comes with the use of standardized, off-the-shelf components that have proven interoperability with each other as well as years of prior service in the wastewater treatment industry. In the unlikely event that a component fails, it can be replaced and the system reconfigured quickly. Hach’s RTC solutions for WWTP applications come with quarterly service and support, including specific service-level agreements. Combined with the PROGNOSYS predictive diagnostic system, WWTP operators can trust in the peak performance of all our RTC solutions.
Strategic simplification with prepackaged RTC solutions can help WWTP operators quickly reduce the variability, complexity, and latency of their processes, while gaining much greater levels of consistency and predictability in the performance of those processes. The peace of mind that comes with those benefits is hard to quantify, much less be used to justify the investment in an RTC solution. However, the cost savings that accrue from dramatic reductions in consumption of chemicals and energy can often provide a return on investment in under a year. In addition, an RTC solution can help ensure continuous regulatory compliance and thereby reduce risks of fines and sanctions.
Hach’s RTC (real-time control) solutions are complete off-the-shelf systems that adjust treatment processes in real time, keeping WWTP facilities compliant while reducing treatment costs. The four baseline systems are:
• RTC-P System: Optimises chemical phosphorus removal by adjusting chemical dosing in real time through the continuous measurement of phosphate concentration and flow, allowing WWTP operators to maintain consistent effluent phosphorus values while reducing phosphorus use for substantial cost savings on chemicals.
• RTC-N System: Optimises nitrification processes by adjusting dissolved oxygen (DO) concentration in real time through continuous measurement of ammonia load, allowing WWTP operators to maintain consistent effluent ammonia values and save energy. Designed specifically for continuously aerated biological WWTPs, it uses both an open- and closed-loop controller for optimal aeration control based on the desired effluent ammonia set point.
• RTC-N/DN System: Designed specifically for oxidation ditches and sequencing batch reactors, this system optimizes nitrogen elimination by determining the optimal times for nitrification and denitrification based on the continuous measurement of ammonia and nitrate concentrations.
• RTC-ST and RTC-SD Systems: Used for sludge thickening and dewatering processes, these RTC solutions can control polymer dosing in real time, helping to significantly reduce polymer dosing costs while also increasing biogas yield and reducing maintenance and guesswork in running sludge processing technologies.
1. Engineering Waste Water Treatment Systems That Work. By Prince Engineering, PLC. Traverse City,