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Industry and municipal waste-water (sewage) treatment plants have had to respond to environmental legislation such as the Urban Waste Water Directive, IPC and the forth-coming IPPC regulations. As successive legislation becomes more stringent, discharge consents have been progressively tightened, and the need for self-regulation has become important. As a consequence, on-line instrumentation has been installed throughout waste-water industry to continuously monitor discharges and record key consent parameters.
Many industries need to comply with a range of consent parameters that may include Flow, pH, Suspended Solids, Ammonia, COD and BOD. The latter two measurements can be determined using laboratory methods on discrete samples giving historic data. However there is a requirement for industry to regulate discharges in real time so where ever possible, TOC analysers have been installed, reporting the dissolved organic carbon content in real time. Since a correlation between the TOC and the oxygen demand can often be established, this is a very powerful parameter. The other determinants are also instantaneous or equally responsive continuous measurements.
Final effluent is typically continuously monitored
for Ammonia and Suspended solids (Turbidity) although other measurements
may also be performed on discrete samples. Ammonia is a critical
parameter since it is toxic to aquatic life and also indicates the
extent of treatment. Rising ammonia concentrations indicates inefficient
nitrification possibly due to poor aeration, insufficient liquor
concentrations, nitrification inhibition due to toxicity, temperature
or excessive hydraulic load. Continuous measurement data is therefore
crucially important to confirm the treatment facility is operating
efficiently. More recently, phosphate consents have also been imposed
resulting in additional treatment and control requirements. |
