Sample preparation is usually necessary for the reliable operation of on-line analyzers in municipal and industrial wastewater treatment facilities. Preparing the sample prevents solids and bacteria from contaminating the analysis system and its components. The sample preparation system and the analysis system must be matched to each other so that accurate and continuous measuring operation can be guaranteed together with low maintenance requirements.
In combination with a suitable sample preparation system, WTW analysis systems provide greater operating reliability and availability.
WTW Sample Preparation Systems:
Biological Treatment:
For the most frequent application of on-line analyzers, their use in the biological treatment of wastewater treatment plants, WTW has developed the PurCon® sample preparation system. In contrast to preparation techniques based on the sedimentation principle, this low-maintenance system provides a constant flow of permeate.
Final Effluent:
For monitoring final effluent, WTW TresCon® Analyzers require no sample preparation. The TresCon®’s AutoClean® feature allows the treated sample to be measured directly.
PurCon® is a continuously operating sample preparation system which has been specially designed for use in wastewater treatment facilities. In contrast to conventional preparation systems, e.g. by sedimentation, the PurCon® unit provides a continuous flow of solid-free and bacteria-free permeate; BubbleClean® feature results in low maintenance requirements. This sample preparation system is suitable for a wide range of applications in the wastewater treatment plants; even for applications in the biological treatment with difficult-to-sediment sludge components.
The PurCon® sample preparation system is the ideal complement to the TresCon® analysis system, as up to three on-line analysis modules can be supplied with permeate simultaneously.
| Permeate | Feed to Analyzer | Continuous |
| Yield | 3.6 l/h max., adjustable in four increments | |
| Quality | Free of solid matter and bacteria | |
| Sample Delivery | Minimum … maximum | 400 ... 1.500 l/h approx. |
PurCon® IS consists of a filter unit 1, that is put directly in the sample, a suction hose 2, a control unit for outside mounting 3, that takes the permeate in and a permeate line 4 for the transport of the permeate to the analyzer units. The permeate line can – according to the ambient temperature conditions at the site – be specified with or without freeze protection.
At the end of the permeate line a box 5, is mounted that delivers the permeate.
| Permeate Stream Sufficient for | PurCon® IS/2-230: | supply of one TresCon® analyzer module |
| PurCon® IS/4-230: | supply of up to three TresCon® analyzer modules |
In the effluent water from thesecondary sedimentation the concentration of solids is often so high that sample preparation is required before on-line analysis can take place. In the effluent from wastewater treatment plant it is possible to carry out on-line analysis with TresCon® without any sample preparation as the analyzer module uses the AutoClean® method; this is a very efficient automatic self-cleaning system.
If TresCon® analyzers are used in slightly loaded wastewater such as wastewater treatment plant effluent the
PF 105 sample bypass is used to provide the analyzer module with unfiltered sample. The unit consists of a Y-shaped pipe branch with a valve for regulating the flow in the bypass. The supply to the TresCon® analyzer can be set with a second fine valve in the sample branch. To protect the TresCon® analyzer module coarse particles are retained by a woven-wire sieve in the branch.
Overflow vessel VB 105 with continuous sample flow is used to feed the analysis modules with non-filtrated sample. The unit is made up of a cylindrical vessel with a volume of approx. 2 l. This vessel is continuously being flown through and thus always supplys up-todate sample.
| Tubing connections | Ø 20 mm dia. |
| Permeate tubing | Length 1 m (1.09 yds), 6 mm (0.24 in.) I.D. |
| Feed | 1000 ... 1500 l/h |
| Branch | Approx. 3 l/h |
Apart from its use in aeration basins, the PurCon® system is ideal for the preparation of samples from the secondary sedimentation stage. In such cases PurCon® also continuously supplies an adequate amount of high-quality permeate. As only residual solids need to be removed from the sample, extremely low maintenance requirements are achieved.
