Monitoring And Instrumentation

Monitoring And Instrumentation
Nutrient analysis system keeps wastewater plant in control

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Nutrient analysis system keeps wastewater plant in control

Problem

The Denver, Colo., Metro Wastewater Reclamation District wanted near real-time nutrient analysis for a challenging headworks wastewater aeration process, consisting of a combination of centrate and RAS. The centrate and RAS reaeration basin (CaRRB) effluent is added to primary effluent prior to mainstream aeration.

Solution

ASA Analytics supplied a centralized nutrient analysis system for CaRRB improvements in 2009, following a two-year period of development, testing, project design and procurement. The system uses a single ChemScan UV-6101 Analyzer and four in-line cyclic filters to monitor nitrate and ammonia from four sample locations within the plant. One of the major benefits of this process is to verify the reduction of very high ammonia generated in the anaerobically digested biosolids prior to mainstream aeration. The project required ASA to develop new calibration methods for ammonia and nitrate, allowing much improved upper detection limits, new types of sample filters that could survive without frequent cleaning in the CaRRB and primary effluent samples, better automatic cleaning methods for the in-line cyclic filters, and addition of ortho-phosphate analysis at two sample locations in 2010.

Result

The system is now approaching five years of reliable operation at the plant and generating real-time nutrient data for process operation and control. 800/665-7133; www.asaanalytics.com.

SCADA solves pressure problems and saves energy

Problem

The City of Winter Park, Fla., was seeing excessive pump run times and unacceptable force main pressures due to multiple lift stations pumping into a single under-sized force main. The cost to design and construct a larger force main was prohibitive. That, along with likely public outcries over construction disrupting a major commercial street, led the utility to look for a solution that didn’t require a larger pipe.

Solution

The utility implemented Data Flow Systems’ TAC II SCADA System with Symphony, Harmonious Pump and Flow Management to coordinate all lift station pumping. Symphony incorporates algorithms that synchronize all pumping minute by minute. This levels out peak flows by managing the force main’s diurnal curve over a 24-hour period without surcharging any gravity sewer mains.

Result

All lift station pumping was precisely coordinated so that pumps were not fighting each other. Pressure spikes were significantly reduced, cutting energy costs by 42 percent, average pump run time by 34 percent and maintenance costs by nearly 50 percent. 321/259-5009; www.dataflowsys.com.

Community moves toward a single SCADA system

Problem

The monitoring and control system for the water and wastewater systems in Ocala, Fla., was built over time by various integrators. The original system included only remote telemetry units (RTUs) with proprietary HMI software at the treatment plants. Programmable logic controllers (PLCs) were then installed in the lift station network, and a third hardware and software system was added to the irrigation sites. It was expensive to train staff on three applications, each system only monitored part of the process, there was no central historian for reporting and analysis, many servers were required to ensure redundancy, and multiple software renewal fees and support contracts were involved.

Solution

In 1995, Ocala began a 15-year transformation to a unified SCADA application by adopting VTScada monitoring and control software from Trihedral Engineering Limited. Because VTScada could communicate with the legacy RTUs and PLCs, there was no need to replace them, and conversion could proceed one system at a time.

Result

Though the process took 15 years, the city never exceeded the yearly budget. The final system included a new approach to distributed historical data management that helped to lower costs by reducing labor at some remote sites. 800/463-2783; www.trihedral.com.



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