Source Water Monitoring
Monitoring water before it enters into the drinking water plant can offer invaluable data to optimize the injection of treatment chemicals as well as detect a change in water quality that could affect the filters or other infrastructure in the plant. For instance, if a diesel tanker ran into the river the drinking water plant pulls water from, letting the water pass the intake would be extremely beneficial to the infrastructure of the treatment plant and distribution system.
In depth overview:
The vulnerability of source waters to contamination attacks is limited by a number of factors including dilution effects and natural attenuation. The fact that the water also has to traverse the treatment plant barrier before it can affect consumers also helps to mitigate the hazard. Even so, the risk of an intentional contamination event, not to mention the risk of an accidental spill, is real. While such an event would be unlikely to cause mass casualties it could severely impact the effected area and deny service to that community for some time.
In November of 2005, an explosion at a PetroChina factory in Jilin province resulted in a massive spill of benzene into the Songhua River in northern China. This extensive spill resulted in contamination of the river water and a denial of service to over 4 million customers in Harbin the capital of China’s northeastern Heliongjiang province. As the spill migrated down river it affected various other cities and even became an international problem when the contaminant plume crossed the border into Russia. This massive spill didn’t result in any casualties but it did cause a panic and hording of bottled water and food in several areas.
This spill was quickly reported and protective action was taken to prevent customer exposure to the contaminated water. A scenario can be imagined where an industrial accident is not reported or a deliberate event occurs to cause a similar incident. If the chemical or material involved was highly toxic and no monitoring was being done, customers could be exposed. This is a good argument for the benefits of monitoring source waters. In fact, source waters are already monitored in several locations throughout the world. The European Community has been a leader in this area for years.
Heavily industrialized areas in Europe such as the Rhine river valley were recognized early on as great potential health hazards. The heavy industrialization along with the large population reliant upon river water in this area made it an accident waiting to happen. A series of industrial mishaps along the Rhine led to the development of an early warning system that could alert utilities down stream of an impending spill so that water intakes to treatment plants could be shut down before the contaminated water reached the plants. These systems make use of on-line monitoring of a variety of physical and chemical measurements of water condition combined with various toxicological methods to determine river water quality. This system has proven to be effective in preventing serious contamination form reaching the treatment plants.
Potential Challenges in Monitoring Source Water:
There are a number of potential problems with implementing a monitoring system for source water. There is the problem of diurnal (night and day) as well as seasonal shifts in water quality due to a variety of factors such as aquatic plant respiration and decaying vegetation from autumn leaf falls. Varying amounts of sediments, turbidity and dissolved solids due to precipitation events and spring run-off fluctuations may be problematic. Monitoring equipment is often exposed to extreme conditions of heat and cold and is often located in remote areas so that power supply and communications become an issue. Due to the transient and unexpected nature of the events we are trying to detect, the monitoring systems also need to be on-line and continuous because, if we knew when we needed to monitor we wouldn’t need to monitor.
One of the chief problems is what to measure. The diverse list of contaminants would make monitoring for individual chemicals or even classes into a futile effort to out guess the terrorists or to be precognitive in surmising what type of accidents will occur. This suggests that rather than testing for each chemical or class of chemical on an individual basis some broad-spectrum form of testing should be utilized to monitor for general changes in water integrity. One of the likely candidates for such monitoring would be bulk monitoring of traditional water quality parameters. An on-line system is considered here, as grab samples would be ineffectual as an early warning system.
Which parameter do I test for and why?
The basic concept here is to actively and continuously monitor a variety of basic water quality parameters and look for significant changes that may be indicative of a contamination event. There are a variety of source water parameters that may find application for this sort of system. Various manufacturers in the environmental market have for many years combined a variety of this sort of instrumentation into self contained data collection bundles that can feed data back to a central location via wireless telemetry or hard wired packages. There are a number of parameters currently available for on-line monitoring. See table below.
|Parameter||Applicability to Monitoring|
|Ammonium/Ammonia||May help in detecting byproducts form increased bacterial counts such as a sewage spill|
|Blue-green Algae||Changes can indicate toxicity to the algae|
|Chloride||May indicate presence of chloride containing metal complexes.|
|Chlorophyll A||Changes can indicate toxicity to the algae as in the WaterSentry discussed previously|
|Conductivity/TDS||May indicate presence of ionic species|
|Dissolved Oxygen||Sudden change may indicate toxic conditions that effect algal respiration or increased levels of bacteria using up the oxygen.|
|Dissolved gasses (total)||Changes can correlate with some compounds|
|Light Ambient||May indicate an opaque plume of a toxic compound.|
|Nitrate||May help in detecting byproducts form increased bacterial counts such as a sewage spill|
|Oxidation reduction potential (ORP)||May indicate sudden changes for oxidative or reducing species introduced into the water.|
|PH||Acid base relationships|
|Rhodamine||Tracer used in studies to trace plumes|
|Salinity||May indicate presence of ionic species|
|Turbidity||May indicate some chemical compounds or increased bacterial levels|
|UV Absorption||Capable of indicating changes in concentration of some organic species.|
|General Physical parameters (barometric pressure, depth, temperature etc.)||Little security utilization but can help coordinate and adjust readings from multiple locations|
- Source Water Monitoring [PDF]
- SWMP Success Story [PDF]
- Source Water Monitoring [PDF]