A contour plot technique for depicting wastewater lagoon parameters and analysing their interrelatedness

Most wastewater treatment plants regularly monitor plant performance. Analy sis of the resulting data can provide valuable insights into plant behaviou r. A useful first step in the systematic analysis of such data is to depict them graphically. The resulting plots help identify the more obvious relat ionships between measured wastewater characteristics. They also help in loc ating anomalous data points. In the case of multi-pond wastewater treatment lagoons, finding an informative way of depicting the monitoring data is di fficult. This is because the required data plots need to show not only how measured characteristics vary with time but also how they vary along the po nd chain. Conventional 2-D "time-series" plots are inadequate for this task if the lagoon comprises more than a few ponds, or if the amount of accumul ated data is large. An alternative, contour plot based approach was develop ed that overcomes the problems with conventional 2-D plots. The procedure f or producing such plots is described and factors affecting their accuracy d iscussed. A major advantage of the contour plot approach is that contour pl ots for different parameters can be superimposed. By examining these superi mposed plots, one can learn much about the way different parameters are rel ated. A procedure is described that enables the interrelatedness of any giv en pair of parameters to be systematically characterised. The effectiveness of the contour plot approach is illustrated using data obtained over a 9-y ear period for an 11 (later 10) pond lagoon at the Western Treatment plant in Melbourne, Australia. (C) 2000 Elsevier Science Ltd. All rights reserved .