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Municipal sewage | Specific applications and solutions of ozone in wastewater treatment

Views: 0     Author: Site Editor     Publish Time: 2025-06-19      Origin: https://mp.weixin.qq.com/s/wQFWwDYBKhnrd0PHEbnRBQ

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Ozone, as a powerful oxidant, has extensive applications in wastewater treatment. Its core function lies in oxidizing and decomposing pollutants, eliminating microorganisms, and improving water quality characteristics, thereby addressing complex problems that traditional processes are unable to handle.



1 Handling of Type Classification Differences

According to the source, the classification system for sewage includes industrial wastewater, municipal wastewater, domestic wastewater, commercial wastewater, agricultural wastewater and surface runoff.

Different types of wastewater vary significantly in terms of composition, pollutant characteristics and discharge requirements, and thus require targeted treatment processes.

For instance, industrial wastewater focuses on the removal of toxic substances, while municipal sewage needs to take into account both biological and chemical pollutant control.

Municipal sewage and industrial wastewater are interrelated.

Municipal sewage may contain industrial wastewater that has undergone pre-treatment. For example, electroplating wastewater that has been neutralized and meets standards can be discharged into the pipeline network. And industrial wastewater treatment plants may also receive some municipal sewage, such as cooling water.

Different treatment is required during the process.

Industrial wastewater needs targeted processes (such as chemical precipitation, advanced oxidation) to treat heavy metals and toxic organic substances. The discharge standards are strict, for example, the "Emission Standards for Electroplating Pollutants" GB 21900-2008.

The municipal sewage is mainly treated through biological methods (such as activated sludge process and biofilm process), with a focus on nitrogen and phosphorus removal as well as the removal of conventional pollutants such as COD, BOD and ammonia nitrogen.


2 Core application technology

The following are the common applications of ozone in wastewater treatment and the problems they solve:

Disinfection and sterilization

Ozone can rapidly kill pathogenic microorganisms such as bacteria, viruses, and spores in wastewater, including those resistant to chlorine.

Prevent water-borne diseases, meet the disinfection requirements of wastewater from sewage treatment plants, especially applicable to sensitive fields such as drinking water, hospital wastewater, and aquaculture wastewater.

Decolorization and deodorization

Ozone decomposes soluble organic matter, suspended colloids and iron-manganese ions through oxidation, eliminating the color of the water body; at the same time, it decomposes sulfur, nitrogen and other foul-smelling substances.

Improve the sensory indicators of wastewater, such as the high coloration of dyeing wastewater and the foul smell of landfill leachate, and enhance the water clarity.

Degradation of recalcitrant organic substances

Ozone directly oxidizes or indirectly decomposes large-molecule organic substances, such as phenols, pesticides, and dye intermediates, into small molecules or mineralizes them into CO₂ and H₂O through hydroxyl radicals (·OH).

Improving the biodegradability of wastewater and reducing the biochemical treatment load is applicable to challenging scenarios such as pharmaceutical wastewater and chemical wastewater.

Phosphorus removal and heavy metal removal

Ozone can convert phosphorus into insoluble phosphate precipitates; through oxidation, it converts heavy metal ions (such as mercury, chromium) into high-valent forms, promoting precipitation and separation.

Meet strict phosphorus emission standards and treat industrial wastewater containing heavy metals, such as electroplating wastewater and metallurgical wastewater.

Synergistic application of advanced oxidation technologies

Combine ultraviolet light (O₃/UV), hydrogen peroxide (O₃/H₂O₂) or catalysts, such as activated carbon and metal oxides, to generate highly active hydroxyl radicals, enhancing the oxidation efficiency.

For high-concentration and highly toxic wastewater such as antibiotic wastewater and landfill leachate, we have broken through the degradation limits of traditional processes.

3 Municipal wastewater solution

The pollutants in municipal wastewater are diverse and complex. For ozone treatment, the type of gas source needs to be selected based on the water quality characteristics and corresponding systems should be equipped. The following is a detailed analysis of pollutant types, ozone equipment selection, dosage calculation, and actual cases.

Municipal sewage typically contains the following pollutants, classified by category.


(3.1)Physical pollutants

Suspended solids (SS) are mostly composed of sediment, fibers, plastic particles, etc., accounting for approximately 40%.

The discharge of cooling water leads to an increase in water temperature, causing thermal pollution, such as in power plant effluents.


(3.2 )Chemical pollutants

The organic substances include proteins, fats, detergent residues, pesticides, etc. (COD 200 - 800 mg/L).

Inorganic substances include nitrogen, phosphorus (which causes eutrophication), and acidic or alkaline substances, such as those mixed from industrial wastewater.

The toxic substances contain trace amounts of heavy metals, such as zinc and copper, as well as drug residues, such as antibiotics.


(3.3)Biological contamination

The pathogens include Escherichia coli, viruses such as norovirus, and parasite eggs, etc.

4 Selection of ozone core equipment

(4.1)Ozone generator air source type

Air source:

Suitable for small-scale (<10 kg/h), with ozone concentration of 2-3%, low cost but high energy consumption.

Oxygen source (PSA oxygen production):

Suitable for medium to large-scale (10 - 100 kg/h), with ozone concentration of 8 - 12%, and higher efficiency.

Liquid oxygen source:

Suitable for ultra-large scale (>100 kg/h), with ozone concentration up to 14%, suitable for high-demand scenarios.


(4.2)Power matching

Select according to ozone production (kg/h). For example, if the processing capacity is 10,000 tons per day (33,000 m³/d) and the dosage is 5 mg/L, the required ozone quantity is 16.5 kg/h, and a 20 kg/h oxygen-rich source generator needs to be configured.


(4.3)Supporting system equipment



5 Selection criteria and dosage amount


(5.1)Selection criteria

Water quality indicators: COD, BOD, ammonia nitrogen, color, suspended solids concentration.

Treatment objectives: Disinfection (required concentration: 2-5 mg/L), decolorization (required concentration: 5-10 mg/L), deep oxidation (required concentration: 10-20 mg/L)

Reaction conditions: pH 6-8, temperature < 40℃, contact time 10-30 minutes.


(5.2)Dosage calculation formula

[1000](@ref) - Parameter example:

Water treatment capacity: 10,000 cubic meters per day

Ozone dosage: 5 mg/L (for disinfection and decolorization)


A 60 kg/h oxygen source ozone generator needs to be configured.


(5.3)Challenges and Solutions

Difficulty:

Ozone decomposes rapidly and the addition position needs to be optimized (such as at the front end of the contact tank).

The risk of by-products (such as bromate) needs to be controlled by regulating the bromide ion concentration in the raw water.

High energy consumption (electricity consumption is approximately 10-15 kWh/kg O₃) requires heat recovery or variable frequency control.

Solution:

Utilize catalytic ozone oxidation (such as with TiO₂ catalyst) to enhance efficiency.

Combine ultraviolet/hydrogen peroxide (O₃/UV/H₂O₂) combination to reduce ozone usage.


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