Measurement of Ammonia for Ground and Surface Water Use in Municipal Environments
As global warming increases pressure on the world's water reserves, it is necessary to regulate water consumption and in some cases limit water use altogether.
The most common method used for water disinfection is the use of either chloramines or free chlorine. With the recent introduction of limits on the use of groundwater, it is necessary to develop new techniques of monitoring water quality and in particular obtaining reliable measurements of ammonia, chlorine and chloramines.
Groundwater provides approximately one third of public water supplies across England and Wales. Governments and environmental agencies are now investigating the current and future availability of groundwater, and have introduced a range of initiatives to limit over-consumption.
In addition to concerns over the availability of groundwater, there are significant issues with water quality when groundwater and surface water are mixed. In Europe, most drinking water production companies use chlorine as a disinfectant. It is added to water as chlorine gas, calcium hypochlorite or sodium hypochlorite. For drinking water preparation from surface water, chlorine is used as a primary disinfectant in most cases. However, chloramine is often used for the disinfection of groundwater for drinking water.
When groundwater and surface water mix in the distribution system, the chlorine and chloramine disinfectants combine to form a residual substance which contains ammonia, free chlorine and monochloramine. As a result of the increasing combination of surface water and groundwater, it is essential that water treatment plants are able to carry out accurate monitoring of these chemicals in water to avoid any potential health consequences.
The increasing level of concern over water quality has affected the use of chloramines in the water disinfection process. Chloramine levels are already carefully monitored but added concerns over mixing chloramines with free chlorine have resulted in the increased need to obtain reliable measurements of chlorine and ammonia in drinking water. This means that both incoming and outgoing water sources are monitored at each water storage facility to determine the concentrations of ammonia, monochloramine, and free chlorine.
Ammonia monitoring has traditionally been undertaken by automated versions of ammonia-selective ion electrodes, but these methods are geared towards laboratory applications. These conventional systems generally use expensive, complex and labour-intensive instruments which are difficult to maintain, and often require external service contracts. When using older monitors it is often necessary to install a sanitary sewer at each treatment location to treat the reagents added during the monitoring process, which required safe removal and generated a significant cost. Due to the expense and unreliable nature of old monitoring systems, the need for reliable, safe, accurate instruments has never been higher.
The development of new technology has enabled a completely new approach to simultaneous on-line monitoring of chloramines and ammonia in water which is simpler, cheaper and more stable than conventional monitoring equipment. With this technique, measurements of both ammonia and chloramine can be carried out on one instrument. These new systems provide users with a monitor which is both simple to operate and economical to purchase. This technique has been adopted by Analytical Technology Inc, (ATi) with the development of the new Q45N Dissolved Ammonia Monitor. This system uses reaction chemistry to convert ammonia in a solution to a stable monochloramine compound, equivalent in concentration to the original ammonia level. The chloramine concentration is then measured with a unique amperometric sensor that responds linearly to chloramines while eliminating interface from excess free chlorine in solution.
Much cheaper than conventional monitors, the new technology has the added advantage of allowing direct re-injection of the water withdrawn for monitoring purposes back into the distribution system without the need for additional sewers. Maintenance of the new monitors is simple and easily managed by local people. The new Q45N monitor can also be used with ATi's market-leading free chlorine monitor to provide measurement of free chlorine, chloramines, free ammonia and total ammonia.
The Q45N system consists of a wall mounted chemistry system and an electronic display and alarm package. The chemistry system contains the necessary metering pumps to provide chemical addition to the sample and delivery of the sample to the sensing element. The electronic display and alarm package provides the user interface to the system. Ammonia concentration is displayed on a large format LCD display with secondary display for other operating variables
In 2003 the State of Texas mandated that the amount of groundwater consumed by municipalities should be cut, as aquifers cannot be recharged quickly enough to meet the state's increasing demand for water. In setting out these groundwater protection goals, the authority specified that wherever possible, surface water should be used instead. Since 2003, 51 districts have adopted water management plans, including a North American water utility which serves the Houston area. The combined use of ground and surface water in this area has caused a number of issues to arise concerning the combination of surface and groundwater and the levels of chemical disinfectant resulting when the two are mixed.
ATi's Q45N ammonia monitor and Q45H chlorine monitor are regularly used in the analysis of disinfectant levels. Since the introduction of state limits on groundwater, a Texan water utility has begun to monitor water on both incoming and outgoing streams in order to effectively determine levels of ammonia, chloramines and free chlorine. One panel of the treatment system contains the Q45FN ammonia monitor and a Q45H/62 free chlorine monitor. Each of the water utility's sites requires two panels, and each storage facility has a booster system to reinstate the disinfectant level when the two types of water mix, thereby ensuring that drinking water is properly disinfected and free from potentially harmful reagents.
By using this technology, the water utility has lowered the overall cost of ammonia monitoring. The equipment is easy to use and can be maintained locally, avoiding the need for expensive service contracts. The system also eliminates the requirement for a factory sewer to be installed at each location, as the water drawn can be re-injected into the distribution system.
Authorities and governments worldwide are now investigating levels of water usage, and a wide range of initiatives are being developed in order to regulate and reduce water consumption. Concerns over the quality of groundwater and surface water have motivated water treatment companies to look for more reliable and effective methods of analysis, in order to avoid unsafe and unstable concentrations of chloramines, ammonia and chlorine levels in drinking water. New technologies developed by companies such as ATi have led to the introduction of simple and accurate monitors for the effective measurement of these potentially unsafe by-products of water disinfection. These new technologies provide water treatment plants worldwide with a cost-effective alternative to conventional systems by lowering overall service costs while maintaining high standards of drinking water quality.
For more information about ATi's Q45N Dissolved Ammonia Monitor or any other ATi products please call +44 1457 832800, e-mail firstname.lastname@example.org or visit: www.analyticaltechnology.com
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