Distribution System Monitoring

Iron is tested for corrosion control and to assess if flushing procedures are sufficient in reducing the iron concentration to acceptable levels. Iron testing is also conducted at sites within the distribution system to investigate red water complaints from customers.

Increased water turbidity levels within the distribution system can be an indicator of a water main break, nitrification or other deteriorating water quality conditions. Turbidity is also measured during flushing operations to ensure that it has decreased to acceptable levels before putting the line back into service. Check out Hach's turbidity monitoring solutions.

Monitor pathogenic bacteria and HPCs to ensure that sufficient microbial protection has been achieved and crossconnection errors have not occurred after replacing distribution system mains and service lines.

A decline in pH may be indicative of nitrification occurring in distribution systems using chloramination for disinfection. A sudden rise or drop in pH could also indicate a distribution system failure or security issue.

Some utilities are required to maintain and report certain levels of free chlorine residual for systems using free chlorine for disinfection. Use the indophenol method 10241 for waters that have potential interference due to metals and/or chloramines. This method eliminates over-estimating free chlorine levels. The method also eliminates the use of arsenite for manganese interference compensation.

Check for total chlorine residuals to meet compliance requirements. The maximum level allowed at POE is 4.0 mg/L. Many regulatory agencies require a minimum of 0.2 mg/L free chlorine or 0.5 mg/L total chlorine (monochloramine) throughout the distribution systems. Monitoring is also done at storage tanks and pump stations to study mixing efficiencies, water age, and temperature gradient issues. A sudden loss of disinfectant residual at any point within the distribution system can indicate nitrification issues, line breaks, excessive water age, or possible security violations.

Compare the determined monochloramine value to the value at the POE. A drop in the monochloramine concentration indicates that there is a chlorine demand in the distribution system and the residual monochloramine has been used. A drop in monochloramine would be an indication that the free ammonia level has likely increased, which may indicate the onset of nitrification, and the situation may be out of compliance when only the total chlorine residual is measured by DPD method.

Free ammonia levels will increase as monochloramine reacts with various organics and bacteria in the distribution system water satisfying the chlorine demand. Increased free ammonia levels indicate onset of nitrification. A sudden drop in free ammonia suggests that nitrification is in process and nitrite is being formed. The free ammonia value is useful in determining the amount of free chlorine needed to increase the monochloramine residual at a booster station. The free ammonia level can also be reduced by adding free chlorine in a ratio of 5:1 as Cl2: N to help reduce nitrification potential.

Conduct nitrite monitoring as an early indication of nitrification. Keep concentrations at regulated levels to protect public health and avoid problems within the distribution system.

Monitor your sources for nitrite as it may be present in the source and gets oxidized during treatment to produce nitrate.

Mainly, groundwater facilities aim to remove dissolved metals and/or TOC with pre-oxidation, ion-exchange, or membrane treatment. However, some utilities may employ chemical treatment with coagulants. If your water source requires additional treatment with coagulants to remove colloidal particles, you can use advanced monitoring and optimization tools available from Hach.