Water/Wastewater 5
Thus, based on their weaknesses regarding response time, reproducibility as well as availability for single measurements, these methods did not meet the requirements of the project.
For the efficient, economic and ecological monitoring, analyser systems were required that are characterised by low operational costs, environmentally friendly methods, and reliable results. Due to the de-central installation sites in the tropical country, the analysers need to work autonomously, e. g. the need of service and maintenance has to be minimal. In addition, the toximeter in use should not only work in online mode but also be equipped with the single measurement feature.
The Pre-warning System
Figure 3: Toxicity analyser ToxAlarm at containerised laboratory
Being a project partner LAR AG supplied its toximeter ToxAlarm which is equipped for the online installation as well as the operation in a laboratory. It contains a permanently available, highly sensitive bacteria culture within a well designed fermenter. These bacteria produce independently and constantly new biomass. Additionally, the fermenter is separated from the measuring cell in order to prevent any impairments of the biomass by toxicity of a sample. To ensure sufficient provision of fresh biomass, for each measurement only a small portion is used. This measurement method stands
out through its high reproducibility as the measuring cell is flushed with a cleaning solution after each measurement. Any cross contamination or memory effects of previous measuring processes are avoided. With the ToxAlarm the operator can set up three individual warning levels on the touch screen. This feature makes the system adjustable to the specific requirements of any application. In less than 15 minutes the watery samples are checked for toxicity, giving an alarm in the case toxicity is detected and providing the operator with enough time to take counter measures.
Figure 4: Pump phase and toxic event The Measurement Principle
The biomass consists of very sensitive nitrifying bacteria that consume oxygen in order to convert ammonium to nitrate. This is a natural process and an important part of the biological degradation used in waste water treatment plants. The LAR online toximeter measures this oxygen consumption. Toxic ingredients of the sample will cause an inhibition of the respiration of the biomass. As a result the oxygen consumption will decrease or even stop. Thus, on monitoring the oxygen consumption, well-found conclusions can be made on the toxicity of the sample.
In the first phase of the measurement the sample is pumped into the measuring cell. Any water contains micro-organisms that may have an own oxygen consumption without being affected by toxic substances. Hence, this consumption rate must be considered for the correct result for the sample's effect on the biomass. In the second phase the real measurement takes place. A small portion of the nitrifying bacteria is dosed into the measuring cell which still contains the sample measured in phase 1. Again the oxygen consumption is being determined. The result shows the direct oxygen consumption of the nitrifiers.
When the sample does not contain toxic substances, the curve of
the consumption rate shown on the display will sink significantly. This means that the biomass is active and consumes oxygen. On the contrary, a flat curve will indicate that the bacteria do not use oxygen. They must be inhibited by harmful substances. Within only a few minutes a reliable result is given. Moreover, since the analyser is ready at any time, its measurements allow not only to detect the occurrence of toxic events but also to see when the toxicity concentration decreases again.
Using these toximeter reliable databases from diverse waste water analyses can be set up and are of great importance for the technical and economic planning of the project. The accurate and reproducible results then may be used as basis for the creation of a monitoring programme for industrial zones throughout the country. Since this online toximeter requires minimal service and maintenance compared to other toximeters on the market, it is especially suitable for the de-centralised installation in the south Asian tiger state. The measuring system is able to determine toxicity autonomously as it is ready at any time. By the use of highly sensitive nitrifiers as test organisms, the analyser shows how toxic substances affect the nitrification part of a waste water treatment plant, which is an important biological process, as well as the effects of toxicity on the biology of rivers and lakes.
Microbiological Testing Equipment
The Tintometer Group of Companies (Germany), the home of the Lovibond brand, launches the Microbiological Testing Equipment range, presenting its solutions for indicator organism tests for TVC (Total Viable Count),
E.coli/Coliforms and Pseudomonas. The new Lovibond range is intended to monitor microorganisms – also known as microbes - in the field and is suitable for use by non-technical, semi-technical and professional members of the water analysis team.
This new range also includes an early warning indicative test to detect the pathogenic Legionella bacterium common in many environments, specifically air-conditioning units, cooling towers, domestic water systems and spas. The test detects Legionellapneumophilliaserogroup 1, the most common causative agent of Legionnaires disease in humans, and provides a rapid indication of Legionella presence for further confirmation with laboratory culture tests.
Microbes of various types are found naturally in many water sources. They can be advantageous in some processes. Some, however, can cause disease in both the animal and plant kingdoms. When present in water systems, they can reduce plant and equipment life, potentially affecting the health and safety of operatives and members of the
public.The diversity of the microbes that can affect the water systems is vast and, in the majority of cases, the test to determine which microbial species is the causative agent for disease or infection is too complex to be performed on-site.
It is therefore accepted that indicator organisms can be used in situ to monitor the microbiological trends within a water system: using them as the trigger for changing biocide dosing and further investigative
work.The most commonly used indicator organism tests are TVC (to indicate the general number of microbes in the system),
E.Coli/Coliforms(to indicate any faecal contamination) and Pseudomonas (to indicate any non-faecal contamination).
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www.envirotech-online.com AET Annual Buyers’ Guide 2013
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