HVAC system chemical treatment Importance

Importance of Chilled Water Chemical Treatment In HVAC Systems

Closed Loop :
1.This system is used for the chilled water circulation within the evaporator and AHUs. 2.Closed loop systems are not exposed to the external environment and once a system is charged, there is usually very little water that is needed to be added to the system.3. As the system is isolated from external contamination agents, the water quality at the time of filling up the system is critical.

Advantages of closed loop System:
1.The closed loop system does not have problems of scale formation as there is no evaporation from the system. 2. Eliminates contact with air - which further prevents formation of microbiological contaminants in the system.3.Corrosion of system pipe internal surfaces is reduced due to the absence of oxygen in the system.

Open Loop Systems
1.The condenser water system is an open loop system where water used in the condenser is passed through the cooling tower in contact with air for cooling. 2. Due to the external contact, there are additional challenges for water treatment and quality.

The key issues that the operations team encounters are :
1.Presence of dissolved solids (results in scale formation)2.Corrosion &3.Microbiological contamination.

What is Water?
Water is H2O
Water is a “Universal Solvent”
Water impurities contain dissolved and suspended solids:
Hardness
Alkalinity
Metals (iron, copper, aluminum, zinc)
Carbon Dioxide
Sodium
Chlorides

The following ingredients(Impurities) to be removed to get pure water
Suspended solids
Dissolved solids
Gases
Microbiological life

Possible methods to remove these impurities:

Turbidity(Suspended matter):Coagulation, filtration
Hardness:Softening
Alkalinity:Dealkalization
Chlorides:Demineralization
Iron:Filtration
Impact of Water Chemistry

–Scaling
–Corrosion
–Fouling
–Microbial growth

Microbiological Growth
Microbiological growth is the amplification or multiplication of microorganism.
1.Bacteria’s of Concern
•Pseudomonas
•Desulfovibrio
•Clostridia
•Beggiatoa, Sphaerotilus, Gallionella
•Legionella
2.Fungi
3.Algae
4.Protozoa

Microbiological Growth Environment
•Nutrients (phosphate, nitrogen, organics)
•Ideal temperature (70 to 140 F)
•Ideal pH (6.0 -9.0)
•Proper Atmosphere (oxygen-aerobes/no oxygen-anaerobes)
•Sunlight –Algae
•Wood –Fungi

Microbiological Growth Concerns
•Biofouling
•Heat Transfer Resistance
•Microbiological Induced Corrosion
•Cooling Tower Fill Fouling
•Wood Decay
•Human Health Concerns

Difference Between Oxidising and Non-Oxidising Biocides?
Oxidising biocides attack microorganisms by oxidising (an electron transfer reaction) the cell structure, disrupting nutrients from passing across the cell wall. 

Non-oxidising biocides for industrial use are effective in controlling: Legionella.

Benefits of Chemical Water Treatment
Chemical Testing Equipment
Chemical Safety Equipment(PPE)
Benefits
•Improved performance decrease in energy consumption & operating cost by efficient heat transfers. (Buildings consume over 20% of the world’s water and HVAC systems form a bulk of the use).
Lower blowdown leads to lesser water use, and also reduces the amount of contaminated water from going into the drain water system. •Increase in system life expectancy.
•Minimizes risk of disease.
•Effective and is proven in different areas of application.
Operations and maintenance teams thus need to understand that water quality is very important to not only ensure that the system works effectively – but also to reduce the impact of the HVAC system note environment.

Concerns
•Less environment-friendly than other methods
•Requires proper disposal of chemicals