Water / Wastewater 41


Chromatotec offers a complete and turnkey solution with the TRS MEDOR which is a 24/7 unattended online air monitoring system dedicated on sulphur compounds quantification.


Equipment offers excellent linearity over its entire range of measurement. Alert thresholds are defined to start or stop process according to chemical concentration levels.


The TRS MEDOR monitors the odour control performance and warns the user if process drift appears.


Thanks to a multiplexer unit, one system can monitor odours before and after the deodourisation process in different locations to limit budget.


The TRS-MEDOR includes, as standard, automatic calibration with permeation tube using DMS at 25 ppb and Air generator (Airmopure)


Is MEDOR as sensitive as the human nose?


The results provided in figure 1 illustrate the MEDOR capabilities for sulphur quantification. There are on- line results without any data processing. An NPL(1)


Standard Certified tank was used for the evaluation.


An embedded PC provides odour index and sulphur gas concentrations (In addition, VOC option can be added using others analysers with GC/PID or GC/FID on line instruments).


Recently, the solution allows for the integration of meteorological data from weather stations and dispersion modelling software to display odour and chemical plume to evaluate the odour and chemical impact of the site on neighborhood. It is now possible to integrate data coming from other complementary technologies, display all the results and manage complaints on a unique interface offering the user at-a-glance results from source to environment.


On a specific WWTP several areas were monitored: Screening area (stripping), deodourisation unit area and H2


S filter management area. On screening area: stripping, MEDOR was capable of measuring H2 S and Mercaptans in ambient air.


Compounds like Tertio-Butyl-SH, Propyl-SH, Methyl- Ethyl-S, 2-Butyl-SH or n-butyl-SH were measured in addition. An unexpected Mercaptan for user was discovered in the process. Considered as a confidential one, this sulphur compound may explain some particular events in the process.


The measuring range of the two compounds is between 1 ppb to 1000 ppm. A visual and audible alarm are activated when threshold levels are reached. Equipment are housed in a temperature controlled cabinet to ensure continued reliable operations.


Results are obtained at a glance on a table thanks to VISTACHROM software. Chromatograms can be explored to validate TRS MEDOR performance. An example is given figure 3.


Figure 1 : Chromatogram for Mercaptan and sulphurs using NPL Certified gas bottle


Repeatability tests have been conducted on 19 measurements on MM, EM, DMS, DES. SO2 considered too as it was present in the mixture.


was


The results have shown that sensitivity obtained with a MEDOR is better than the human nose with repeatability at less than 5% for Mercaptan and sulphur compounds. This enables the ability to anticipate odour issues before they affect our human nose.


Average(*) concentration (ppb)


METHYL-SH (MM) 4,87 ppb ETHYL-SH (EM) 4,48 ppb DMS DES SO2


Figure 2 : Repeatability results (*) number of measurements: 19


Case study with the TRS MEDOR in WWTP


Several WWTP as prestigious as SIAAP in France or stations in the UAE have placed for years a lot of trust on Chromatotec solutions.


A measurement network has been deployed onsite and data was centralised on SCADA systems.


The quantification of gases was conducted according to the methods ISO 6326/2 & DIN51855/7 ASTM D 7493-08. It was possible to monitor with one unique instrument and multiplexer several points of interest focusing on Mercaptans (H2S/MM/ EM/PM), sulphurs (DES/DMS/DMDS) or SO2


.


To ensure the performance and the representativeness of measurement, automatic calibration (AIRMOCAL) was performed to automatically validate the results and this, without any human intervention.


Standard deviation (ppb)


Repeatability (%)


5,02 ppb 5,54 ppb 5,20 ppb


0,24 ppb 4,86% 0,14 ppb 3,07% 0,17 ppb 3,41% 0,23 ppb 4,15% 0,29 ppb 5,59%


Limit Of


Quantification - LOQ(2)


0.11 ppb 0.11 ppb 0.19 ppb 0.26 ppb 0.12 ppb


Human nose detection threshold (3)


~0.25 to 40 ppb ~ 0.3 to 20 ppb ~ 1 to 6 ppb ~ 2 to 20 ppb


500 to 3000 ppb


Figure 3 : Quantification on Screening Area (stripping)


One TRS MEDOR was located at the outlet of the stripping process on deodourisation area. It monitors H2


and money by reducing and optimising the consumption of calcium nitrate used. The second TRS MEDOR was located on a Hygiene, Sludge dewatering and H2


S concentrations and pilot the adjunction of calcium nitrate allowing users to save time S filter management


area. ATEX certified, this TRS MEDOR was located in a harsh environment with a measurement cycle of 3 minutes. It was used to check filter performance with only one unit coupled with a stream selector.


This installation allowed users to check gas emissions from 5 digesters, and provided warnings when replacement of the filter was needed.


TRS MEDOR: ALTERNATIVE SOLUTION FOR ODOURANTS MONITORING ON WWTP With the quantification at low ppb of H2


S, MM, EM, DMS, DMDS, DES, SO2


, the TRS-MEDOR


may be considered as one of the Best Available Technologies for sulphurs analysis in ambient air. With LOQ of less 0.3 ppb and repeatability of less than 5% for Mercaptans (MM & EM) and sulphurs (DES & DMS), the system offer full traceability with peak areas for each molecule. TRS concentration is evaluated by calculations considering H2


Additionally, the instrument shows his capability to detect and quantify SO2 equipment. Generally SO2


S, MM, EM, DMS, DES, and DMDS. with the same


is measured using Fluorescence detector. New predictive algorithm allows to define an odour index in WWTP to give a full understanding of emission generation and predict odour and chemical impact. Additionally, the internal auto calibration allows users to automatically validate the robustness of the results.


(1) National Physical Laboratory in UK


(2) LOQ= Low Quantification Limit in automatic / LOQ calculation with minimum area value of 2 000 (amplification 3)


(3) ADEME and INERIS sources


The World´s Smallest Optical Oxygen Meter


The ultra-compact Piccolo2 is a high-precision fiber-optic oxygen meter featuring the proven REDFLASH technology from Pyro Science GmbH (Germany), standing for high precision and reliability with low power consumption and rapid response times.


The Piccolo2 can be used with a variety of optical oxygen sensors for measurements in aqueous samples and in the gas phase. The sensors comprise robust probes, dipping probes and contactless sensors like oxygen sensor spots (for measurements through 20 mm thick windows), respiration vials, flow-through cells and our new oxygen nanoprobes.


The functionality of the Piccolo2 can be enhanced by the optional available climate module PiccoTHP, offering automatic temperature and pressure compensation of the oxygen measurements, as well as precise and simple 1-click oxygen sensor calibration. For OEM applications, the Piccolo2 is also available as OEM version, characterised by ultra-low power consumption and offering automatic temperature compensation of the oxygen measurements. Please contact Pyro Science for more information about high-precision sensor systems.


For More Info, email: email:


For More Info, email: 31548pr@reply-direct.com www.envirotech-online.com IET September / October 2014


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