Chemical Processes
Chemical Processes
The chemical processes covered by this company's services include various disinfection processes such as ozonation, chlorine dioxide, chlorination, and electrochlorination, as well as coagulation and flocculation processes, including electrical coagulation and flocculation.
Disinfection Systems
Disinfection Systems
Disinfection of water is carried out to eliminate pathogenic microorganisms. The most common method of water disinfection is the use of chlorine gas and its compounds, but there are other methods as well, such as ozonation, ultraviolet radiation, and so on.
Chlorination System
The use of chlorine is the cheapest method of disinfecting water and wastewater. Chlorine is used to eliminate bacteria and other microorganisms present in drinking water reserves. Nowadays, even small water reserves are continuously chlorinated. The first application of chlorine in drinking water treatment was for controlling taste and odor. Other applications of chlorine include algae control, removal of iron and manganese, elimination of hydrogen sulfide, and color removal. Chlorine is available in the water industry in various forms, including solid hypochlorite of sodium and potassium and gaseous chlorine dioxide.
Principles of Chlorination
To ensure proper chlorination, the following rules must be observed:
The water to be disinfected should be clear and free from turbidity.
The required chlorine for water must be determined; the breakpoint chlorine and free residual chlorine are important.
In any case, a contact time of about one hour should be considered to eliminate microorganisms sensitive to chlorine.
A minimum residual chlorine of 0.5 mg/L after one hour is recommended. This amount may increase to 1 mg/L in cases of widespread intestinal diseases.
The required chlorine for any type of water equals the amount of chlorine added to maintain 0.5 mg/L residual chlorine after one hour.
Chlorination Methods
Depending on the water volume and project size, the chlorination method is determined. Chlorine may be available in one of the following forms:
a) Chlorine gas (Cl₂)
b) Chloramine (NH₂Cl and NHCl₂)
c) High Test Hypochlorite (H.T.H)
d) Chlorine dioxide (ClO₂)
Chlorine is the first choice in water disinfection because it is cheap, effective, and easy to apply. To prevent its toxic effects, it is added to water through chlorination equipment. Ammoniacal chlorine is also used for water disinfection, but its effect is slower than chlorine, limiting its use.
High Test Hypochlorite (H.T.H) or strong calcium hypochlorite is a calcium compound containing 60–70% chlorine. Solutions made from H.T.H and other chlorinated compounds are used for water disinfection.
H.T.H (Ca(OCl)₂) is prepared as a powder or fine crystal in specified packages.
White chlorine powder Ca(OCl)₂ with 33.5–39% available chlorine.
Sodium hypochlorite (NaOCl) solution containing 3–16% available chlorine by weight.
Despite side reactions of chlorine with organic matter in water and potential health risks, chlorine is still used as a disinfectant for improving drinking water quality.
UV System Performance
Nowadays, the use of UV radiation is expanding in water treatment as a disinfectant due to its lack of adverse effects on the environment. Generally, the performance of ultraviolet systems in water disinfection involves producing UV light at a wavelength of 254 nm using low-pressure mercury lamps or a polychromatic output with wavelengths from 200 nm to infrared and visible light using medium-pressure UV lamps. The optimal wavelength for disinfection is around 260 nm.
The UV mechanism for destroying microorganisms involves absorbing high-energy UV photons by the DNA, which interferes with microbial replication and disrupts microbial tissue. Due to the mode of action of UV radiation, experts have been able to artificially produce these specific wavelength UV rays. UV application is considered a new option for drinking water disinfection compared to ozone gas, which has high capital costs, and chlorine gas, which leaves harmful by-products in water. UV not only eliminates microbial reproduction and destroys bacteria but also effectively inactivates chemical-resistant parasites such as Cryptosporidia and Giardia.
Ozonation Unit Performance
Ozone plays an important role in water and wastewater treatment as an oxidizing agent and disinfectant. Ozone is an allotrope of oxygen, a bluish gas, and unstable. Nowadays, the use of ozone is increasing due to its advantages over chlorination. Ozone has about 25 times stronger oxidation capability than chlorine and is safer to use. Excess ozone gas decomposes without harming the environment. The mechanism of ozone in microbial removal is based on the disruption and direct destruction of bacterial cell walls. In contrast, chlorine’s chemical mechanism is less clear, likely involving penetration of the cell wall, attacking enzymatic groups, and consequently destroying microorganisms.
AOP Process
The Advanced Oxidation Process (AOP) is one of the treatment technologies that can be used to reduce the harmful health and environmental impacts of industrial wastes. In the Advanced Oxidation Process (AOP), hydrogen peroxide (H₂O₂), ultraviolet (UV) radiation, ozone (O₃), and/or a catalyst are combined to remove residual organic compounds (BOD, COD, TOC) effectively. The primary goal of designing advanced oxidation processes is the production of hydroxyl radicals, which are highly efficient in destroying organic compounds.
Advantages:
– The advanced oxidation process requires less ozone and delivers better results compared to conventional ozone treatment systems.
– Reduced ozone consumption and shorter retention time make this system economical for treating high wastewater flow rates.
– This system achieves over 95% reduction in pollutant loads (BOD, COD, TOC).
– Effective removal of organic compounds such as dyes, proteins, surfactants, oils, greases, and more.
– Treatment and recycling of wastewater from textile industries, petrochemical industries, food industries, and others.
– No production of unpleasant odors.
– Fully automated system.
– High reaction speed.
– Minimal space requirement.
– Potential to reduce toxicity and convert treated organic materials into mineral compounds.
– No production of compounds requiring additional treatment, such as carbon consumed in activated carbon adsorption.
– No dilution or generation of secondary wastes for subsequent treatment processes like membranes.
– No sludge production, unlike chemical, physical, or biological processes (biological sludge waste).
– Unique in that no other method allows multi-step treatment of organic compounds within a single process.
NOX Process
NOX – Addition of Nitrogen Oxides
The use of nitrogen oxides is a new process that can be applied to control Nitrosomonas microorganisms. Nitrosomonas have a distinct and well-defined metabolism and can obtain their required energy through aerobic or anaerobic oxidation of ammonia, or via denitrification using hydrogen or organic compounds as electron donors.
In this process, approximately 50% of the ammonia is converted to nitrite, and the produced nitrite serves as the final electron acceptor, resulting in the production of nitrogen gas (N₂):
[
3 NH₄^+ + 3 O₂ + 3 [H] → 1.5 N₂ + 3 H^+ + 6 H₂O
]
Nitrosomonas consume ammonia and NO₂ in a 1:1 ratio autotrophically, producing an equal amount of NO. During denitrification of nitrite to N₂, a small amount of N₂O is generated. Tiny amounts of NO and NO₂ (NOX) may be added to shorten the nitrification/denitrification pathway by Nitrosomonas, thereby providing a regulatory signal for denitrification activities.
Nitrite concentrations up to 50 ppm have no effect on autotrophic Nitrosomonas, but NO concentrations above 25 ppm inhibit ammonia oxidation. Consequently, in the NOX process, the nitrification step is more efficient due to 50% lower oxygen requirement, while the subsequent denitrification step requires up to 80% less organic compounds. This process can be implemented in existing wastewater treatment plants with minimal financial cost and minimal operational strategy changes.
Electrocoagulation Process
Electrocoagulation (EC) Process
In recent years, the electrocoagulation (EC) process has emerged as an effective method for treating industrial wastewater.
This process uses a direct electric current to generate soluble metal ions. The coagulant in this process is produced through the dissolution of a sacrificial anode, accompanied by the generation of hydrogen and hydroxyl ions at the cathode. When the metal ions are provided by EC, they neutralize the oppositely charged pollutant particles in the wastewater, causing them to settle as high-resistance solids.
Additionally, the hydrogen bubbles formed allow the suspended materials to float. EC is ideal due to the advantage of producing a combination of multivalent cations via anode oxidation and floating pollutants on the solution surface, which facilitates their collection and removal.
