Control of organic load in drinking water – Part II

Objectives to be developed in this article:

1. Improved efficiency of chemical addition in the coagulation-flocculation process.
2. Early detection of activated carbon filter saturation.
3. Decreased energy consumption in UV disinfection control and increased lamp life.
4. Water storage: ensure drinking water quality by continuously measuring organic contaminants prior to distribution.

Let’s remember where we can measure the organic load in a drinking water plant

The first part of the water intake was treated as follows

COAGULATION-FLOCCULATION-SEDIMENTATION

Coagulation / flocculation followed by sedimentation / filtration is a process to remove suspended solids of organic and inorganic nature from drinking water.

• Monitoring of the effective removal of natural organic matter (NOM) in the coagulation and sedimentation process.
• Improved process monitoring, improving efficiency and effectiveness of chemical addition and energy consumption.

Microorganisms + NOM + disinfectant ———> Microorganisms destroyed + disinfection by-products (DPB), associated with various types of cancer. Limited in RD 140/2003.

The following graph shows the formation of the main and most elementary of these by-products, chloroform, as a function of the chlorine applied and contact time, in a given water

FILTRATION

• Monitoring of the effectiveness of the activated carbon filtration process allowing improved forecasting of the extent of filter saturation, thus minimizing unexpected downtime.
• Measurement before and after the activated carbon filter.

Tendency to decrease the difference between input and output.

Correct levels of SAC 254nm at the outlet of the active carbon filter

UV DISINFECTION

Verify and optimize correct UV disinfection.

• Process control, enhanced by monitoring the effectiveness and efficiency of UV disinfection.
• UV light with wavelength <280nm destroys the DNA of microorganisms.
• The disinfection efficiency is given by the formula:
  UV intensity (expressed as energy per unit area) x resistance time.
  The appropriate UV dosage for each application must take into account water quality, arc tube aging, industry specifications and microbiological standards.
• Decreased energy consumption for UV disinfection control and increased lamp life

WATER STORAGE

• Ensures drinking water quality by continuously measuring organic contaminants prior to distribution.
• Control of the organic load is especially important if chlorine is used as a disinfectant, as it reacts with organic substances and forms disinfection by-products that are potentially carcinogenic, such as trihalomethanes (THMs) and haloacetic acids (HAAs).

Correlation with various carbon-based parameters is also possible, provided that the composition of water pollutants remains constant.

Common correlations:

• COD chemical oxygen demand
• TOC: total organic carbon
• BOD. biochemical oxygen demand

AMI SAC 254: GUARANTEES THE QUALITY OF DRINKING WATER WITH GREATER SAFETY

1. In surface water, the natural organic load can be very variable, so online detection can be very important to optimize treatment and ensure consistently high water quality.
2. Disinfection by-products prevention and abatement (SPD)
3. Optimization of flocculant and/or coagulant consumption.
4. Checking the operation of decanters.
5. Status trends of activated carbon filters.
6. In case of using UV disinfection, analyze the SAC 254 to know the status of disinfection.