ENVIRONMENT & MUNICIPALITIES
Environmental monitoring is closely related to municipal water monitoring applications. Either it is monitoring of wastewater dirscharge into public water bodies or for treatment of drinking water from surface water or ground water. Furthermore, in regions where potable water resources are scarce, online water monitoring helps to control processes of desalination facilities.
On the other hand, discharge control of wastewater from municipal and industrial sources, both into wastewater treatment plants and into public waterways such as rivers and lakes, is of great importance when it comes to resource preservation and environmental protection.
Especially in regions with limited water resources, potable and industrial water is produced by desalination plants across coastal areas.
Common methods of desalination processes:
Reverse osmosis (RO):
Saline water is pressed against a membrane. When overcoming the osmotic pressure, the membrane allows only the solvent to pass it. The solutes, in this case salts, are held back. As the osmotic pressure of the rest of the salt solution is increasing steadily, it must be discharged. Otherwise, there is the risk of a pressure equalization, which causes the process to stop. Since the RO membranes are very sensitive to organic pollution, an accurate and reliable monitoring of the RO inlet is of great importance to prevent biological growth and impairments of the process.
Multi-stage flash evaporation:
Saline water is heated up to 115°C degrees within a so-called brine-heater. Subsequently, the water is lead through several flash stages with each increased pressure, whereby the steam condenses to salt-free water.
Membrane distillation:
Warm saline water is separated from a cooler interface by a membrane, which only allows water steam to pass it. This process is powered by an electrical field, static pressure difference or by a concentration gradient. When the water steam condenses, salt-free water is produced.
Wastewater that is discharged into municipal wastewater treatment plants (WWTP) may come from both industries and municipalities. The different loads of the water place the greatest demands on the process control of the WWTP to maintain low contamination of effluent water / treated wastewater which is usually discharged into public waterways.
Monitoring on inlet
- Process control of treatment processes by stable inlet loads
- Process safety and protection of biological treatment (nitrification, activated sludge, aeration) based on incoming loads (biochemical oxygen demand, BOD, and toxicity)
- Anaerobic digestion based on oxygen demand of incoming loads
Monitoring of outlet to control treatment performance
- Organics (TOC, COD)
- Nitrogen and phosphate compounds due to their high nutrient input
- organic trace elements / micro pollutants gain importance in terms of environmental protection
Depending on the region, drinking water from ground water or surface water is treated by means of chlorine or ozone processes as it usually contains natural organic matter (NOM).
Organics combined with chlorine will create hazardous substances – Disinfection By-Products (DBP)
- Trihalomethanes (THM)
- Haloacetic acids (HAA)
- Bromate
- Chlorite
Formation of DBP depends on temperature, water pH, time, disinfectant dose, type and concentration of organics.
Monitoring of inlet water
- Control of source water to ensure product quality
- Dosing of disinfectants based on incoming organic load
- Will reduce risk of DBP formation
Monitoring of outlet water
- Maintain high product quality by monitoring organic content
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