Any successful control system relies on the performance of its corresponding instrumentation (either on-line or in-situ) and the instrument’s auxiliary systems such as sampling and filtration. The Instrumentation Testing Association (ITA) conducted a side-by-side comparison of both online and in-situ ammonia analyzers at the City of Houston, Beltway Wastewater Treatment Plant (ITA, 2001). Although all stakeholders benefited by participating in the test project (ITA, 2000), testing was limited to ammonia analyzers. Testing nitrate analyzers for the purposes of controlling nitrification and denitrification would provide an additional benefit for controlling nitrogen compounds in wastewater treatment. The use of on-line nitrogen analyzers can be used to optimize nitrogen control and maximum efficiencies, which can be achieved by combining online nitrogen instruments with a control system.
Assessing performance of on-line nitrate analyzers
Traditionally, activated sludge processes were designed to remove organics and suspended solids from wastewater. The justification for including nitrogen control in wastewater treatment facilities began with the need to protect receiving waters from the increasing problem of eutrophication and hypoxia (low levels of dissolved oxygen in bottom waters, generally less than 2 mg/l). One of the challenges facing wastewater treatment plants in eliminating nitrogen compounds from their effluent comes with the ability to create an optimal aerobic environment to achieve nitrification and an optimal anoxic environment to achieve denitrification, yet without causing an interference with the other processes. This challenge is significantly magnified when the treatment limits are at the limit of technology.