Effects of different seasons on the installation and maintenance of a water treatment unit
The effects of different seasons on the installation and maintenance of a water treatment unit have many different aspects. The fall seasons, whether in the height of summer or in winter, not only affect our water use but also the efficiency of our water and wastewater treatment. Water use rates generally rise significantly during the summer months, especially in areas that receive less (or no) rainfall. Whether you’re watering your lawn or garden, filling your pool, or using tap water to make ice for your drinks, water use is higher when temperatures are higher. With fall already here, and winter quickly approaching, domestic and agricultural water use is declining.
But water use is not the only factor affected by weather and seasons. Some processes used in water and wastewater treatment are also affected. From chemical efficiency to contaminant removal rates to biological activity, to equipment functionality, to the amount of dissolved oxygen available to assist in biological or chemical processes, temperature affects the effectiveness and efficiency of water and wastewater treatment. Admittedly, this is not the most common thought on everyone’s mind when witnessing the change of seasons.
Effects of different seasons and climate change
Water temperatures are expected to rise as a result of climate change. This may exacerbate other changes expected to occur, such as increased nutrient loading, increased frequency, duration, and intensity of algal blooms and cyanobacterial blooms, and increased variability in the amount and nature of runoff. Higher water temperatures may also expand the geographic range of microorganisms associated with waterborne diseases.
The effects of climate change will increase the importance of monitoring water quality, selecting the appropriate treatment process, and day-to-day control of operations and distribution system operations.
Temperature effects
Temperature can affect the physical, chemical, microbiological, and biochemical aspects of water. It is important to understand how temperature can lead to health and aesthetic contaminant issues when developing and implementing management strategies. Some important considerations are highlighted below.
Viscosity
The viscosity of water is higher at lower temperatures (i.e., it generates greater resistance or drag).
Some particles may not stabilize at cold temperatures; This may lead to the migration of particles (turbidity) from sedimentation processes to filtration processes; Filtration processes are also less effective at cold temperatures.
Conductivity
As the water temperature increases, the conductivity (i.e. ionic activity) increases.
Conductivity is a surrogate measure of total dissolved solids that may affect the taste of water, corrosion, or mineral deposits. Conductivity measurements should be temperature corrected to 25°C (known as specific conductivity) to facilitate comparison of results.
Boiling and melting points
Boiling and melting points determine the “state” of a substance (e.g., solid, liquid, or gas). In some documents, vapor pressure or Henry’s Law constant is a measure of compound volatility (ie the ability to evaporate from a liquid).
Odor
In general, the higher the temperature, the greater the formation of odor-causing compounds and/or the intensity of the odor.
Odor-causing compounds can be produced by chemical reactions (eg chlorophenol) or by microorganisms (eg geosmin). However, it is the physical process of evaporation (e.g., compound volatilization) that leads to the sensory reaction.
pH
As the temperature decreases, water dissociation decreases and the pH increases. This means that the pH value at which water is considered acidic, neutral, or basic varies with temperature:
25°C neutral = 7
20°C neutral = 7.085
5°C neutral = 7.365
0°C neutral = 7.5
There are a number of points to consider:
- pH meters must include a temperature compensation device; The pH should be measured as soon as possible after sample collection to minimize the effect of temperature.
- A solution with a pH of 7 at 5°C is acidic because its pH is below the neutral value of 7.365 at that temperature (i.e. there is an excess of hydrogen ion [H+] versus hydroxide ion [OH-]).
- Coagulant processing plants at acidic pH operate farther away from the neutral pH of 5°C than at 25°C, and much less OH- is available to react with the coagulant. Seasonal pH adjustment is suggested to account for lower OH concentrations during cold water conditions.
- Chemically affected processes in the distribution system, such as corrosion, depend on pH.
Melting of solids
The solubility of most solids increases when the temperature increases. But there are some notable exceptions, including:
- Calcium carbonate
- Calcium hydroxide
- Calcium phosphate
- Magnesium silicate
- Sodium hydroxide
There are a number of points to consider:
- The solubility of metals generally increases with temperature; Therefore, only cold tap water should be used for drinking, cooking, and preparing infant formula.
- A change in temperature can cause materials to settle and form deposits or can cause previously deposited materials to dissolve and release deposited contaminants.
- The effect is difficult to predict and can vary from one system to another because the solubility of many compounds also depends on pH.
Solubility
Gases decrease as temperature increases (i.e. cold water contains more dissolved gas than warm water). Important dissolved gases relevant to drinking water include ammonia, carbon dioxide, and oxygen.
There are a number of points to consider:
- Ammonia, when present in raw water, creates a high oxidation demand and reduces disinfection effectiveness; It is a nutrient that encourages algae growth at the source and biofilm growth in the distribution system; Nitrogenizing bacteria convert ammonia into nitrite/nitrate.
- Carbon dioxide has a significant effect on pH stability; Groundwater supplies containing dissolved carbon dioxide should use an online pH meter or a space-free meter to obtain accurate results.
- Oxygen has a significant effect on redox conditions. This affects microbiological community composition and redox state-dependent changes in solubility (e.g., manganese release under anoxic conditions); Warmer water temperatures due to climate change are expected to reduce dissolved oxygen content and increase the risk of hypoxic conditions.
Effects of different seasons on rates of chemical reactions
In general, every 10°C increase in temperature doubles the reaction rate.
There are a number of points to consider:
- Chemical oxidants and reduction will be more effective at warmer temperatures, so temperature is an important factor to consider when using chemical oxidants to inactivate pathogens.
- Decomposition of disinfectant residue in the distribution system accelerates at warmer water temperatures.
- The rate of formation of disinfection byproducts generally increases with increasing temperatures.
- Hydrolysis products form faster at warmer temperatures, making the process more efficient.
- Hydrolysis of polyphosphate increases with temperature and may release previously trapped manganese.
- The rate of diffusion is related to the movement of molecules and increases at warmer temperatures (e.g., diffusion of oxygen and metals).
Microbiological aspects
The effect of temperature on microbiological aspects depends on the microorganisms and their location in the aquatic system. For example, some microorganisms survive best at lower temperatures in source water, while others thrive at warmer temperatures in the distribution system or within residential and building plumbing systems.
Biofilms (such as bacteria, protozoa, and fungi)
Microbial activity increases with temperature, but biofilms can survive and grow at all temperatures encountered in the distribution system (below 4°C to 30°C).
The formation and growth of biofilms cause many water quality problems. For example, biofilms can:
- Harboring pathogens for later release.
- Consumption of leftover disinfectants.
- Generation of organic matter (e.g., precursors of disinfection byproducts).
- Generating turbidity, color, or unpleasant tastes/odors.
- Mediates corrosion and release of metals (e.g. lead, copper).
Nitrogenous bacteria
Optimal growth occurs between 20°C and 30°C, but nitrifying bacteria can survive and grow at all temperatures encountered in the distribution system (below 4°C to 30°C).
In addition to the biofilm effects mentioned above, nitrifying bacteria convert ammonia into nitrite and nitrate.
Effects of different seasons and therapeutic operations
The effects of different seasons on all physical, chemical, and biological treatment processes, especially temperature. Therefore, it is important to understand seasonal trends. Process modifications or additional processes may be needed to effectively manage the effects of temperature and water treatment throughout the year.
