Water treatment is an essential part of many industrial and technical processes. It comprises all measures that change the physical, chemical and biological properties of raw water in order to make it usable for the respective purpose. In practice, water treatment aims to remove impurities, optimize water quality and meet the legal requirements for water for various applications.
Table of contents
Importance of water treatment
Water treatment is not only used to produce drinking water, but also plays a central role in industrial processes and wastewater treatment in particular. Untreated water can cause system corrosion, fouling, deposits or biofouling and significantly impair the efficiency of technical processes. In addition, the reuse of water in cycles is a key to conserving resources.
Areas of application:
- Industry: Process water for the chemical, food, metal and electronics industries.
- Power plants: Feed water for steam boilers and cooling water systems.
- Water recycling: recycling water in industrial plants to conserve resources.
- Wastewater treatment: Pre-treatment and treatment of wastewater to comply with discharge limits.
Process stages of water treatment
Water treatment takes place in several coordinated stages, which are individually combined depending on the raw water quality and intended use.
1. pretreatment
Pre-treatment is used to remove coarse impurities from the raw water and to protect the downstream stages from overloading or damage.
Screens and strainers:
Mechanical devices that retain coarse solids such as branches, plastic parts or larger particles. These components are particularly important in the treatment of surface water or industrial wastewater with coarse contaminants.
Technical aspect: Mesh sizes vary between 1 mm (fine screens) and 100 mm (coarse screens) depending on requirements.Grit trap:
Separates heavier, sedimentable particles such as sand, silt and mineral deposits by gravity. This reduces wear on pumps and pipelines.
Typical designs: Horizontal grit traps or circular grit separators with air supply to improve separation.Oil separator:
Removes free, floating oil and grease from the water. These separators utilize the density differences between oil and water and can optionally be supplemented with coalescence filters to increase efficiency.
2. main treatment stages
The main treatment stages are the core of the water treatment plant. Physical, chemical and biological processes are used here to remove dissolved, colloidal and organic impurities.
Physical procedures
Filtration:
Filtration systems, such as multi-layer filters or disc filters, remove particles and suspended matter.
Technical aspects:- Filter materials such as quartz sand, activated carbon or anthracite.
- Backwash function for cleaning the filters.
Photo: Our ALMA FIL multi-layer filters with downstream ALMA ION ion exchangers
- Ultrafiltration (UF):
Removes particles, viruses and bacteria through membranes with pore sizes of 0.01-0.1 micrometers. - Nanofiltration (NF):
Reduces hardness formers such as calcium and magnesium. - Reverse osmosis (RO):
High-pressure process for removing salts, organic substances and micropollutants. Ideal for the production of pure or ultrapure water.
- Ultrafiltration (UF):
Sedimentation:
In sedimentation tanks or lamella clarifiers, heavy particles sink to the bottom by gravity, where they can be collected and removed. Sedimentation is often used as a precursor to chemical or biological processes.
Photo: Our ALMA OSMO reverse osmosis system for in-house water recycling
Chemical processes
Precipitation and flocculation:
Chemical reagents such as iron or aluminum salts are used in CP systems to convert dissolved pollutants into solid particles. Flocculants (polymers) promote the formation of stable flocs.- Ozone, chlorine or hydrogen peroxide oxidize organic pollutants and micropollutants.
- Advanced Oxidation Processes (AOPs): Highly reactive hydroxyl radicals decompose even substances that are difficult to break down.
Ion exchange:
Ion exchange resins specifically bind dissolved ions (e.g. heavy metals, hardness formers) and exchange them for harmless ions such as sodium or hydrogen.
Photo: Example of a CP system for the removal of heavy metals, AOX and hydrocarbons(ALMA CHEM MCW)
Biological processes
Activated sludge process:
Microorganisms break down organic loads aerobically. The process is particularly effective for reducing COD (chemical oxygen demand) and BOD (biochemical oxygen demand).Biofiltration:
Organic substances are biodegraded in bioactive filters with microbially colonized media. Used in pre-treatment before membrane processes or in the treatment of process water.Anaerobic reactors:
Without oxygen, microorganisms convert organic substances into biogas (methane and CO₂). These processes are ideal for highly concentrated industrial wastewater.
Photo: Our ALMA BHU GMR biogas plant for generating energy from wastewater
3. follow-up treatment
Post-treatment ensures that the desired water quality targets are achieved. It is particularly important for sensitive applications such as cooling water, boiler water or when complying with legal discharge limits.
UV disinfection:
Ultraviolet light destroys the DNA of bacteria, viruses and parasites and prevents them from reproducing. UV disinfection is chemical-free and fast.Polishing:
- Fine material filtration using activated carbon or membranes removes the last organic residues and suspended solids.
- Objective: Achieving pure water quality or freedom from residual substances for specific applications.
pH adjustment:
Acids or bases are dosed into neutralization systems in order to adjust the pH value to the requirements of the downstream processes or the discharge limits.
Photo: Activated carbon filter installed in GRP tanks(ALMA Fil AK)
Key technological processes: CP systems, biofiltration and membrane systems
Choosing the right key technologies in water treatment is crucial to ensure efficient treatment and reuse of water. Chemical-physical plants(CP plants), biofiltration and membrane plants (especially reverse osmosis) are three central technologies that each address specific challenges and, in combination, achieve optimal results for industrial water treatment and water recycling.
1. chemical-physical plants (CP plants)
Why CP systems are a key technology:
CP systems are indispensable for the pre-treatment of wastewater containing heavy metals, which is produced in many industrial processes, e.g. in metal processing, electroplating or surface treatment. They treat the wastewater so that it can be efficiently recycled in downstream reverse osmosis systems.
Technology and functionality:
- Neutralization: The pH value is adjusted to an optimum range by adding acids or alkalis to enable the precipitation of heavy metals.
- Precipitation: Dissolved heavy metals (e.g. nickel, zinc, chromium) are converted into insoluble hydroxides by adding precipitants (e.g. milk of lime, ferric chloride).
- Flocculation: Flocculants promote the formation of stable particles that are easier to separate.
- Sedimentation: The solid particles sink to the bottom of a sedimentation tank, where they are collected and disposed of.
Areas of application:
- Pre-treatment for reverse osmosis systems: Heavy metals and other critical substances must be removed prior to membrane filtration in order to prevent fouling and scaling of the membranes.
- Industrial applications: Wastewater treatment to comply with legal limits before discharge into the public sewer system.
Advantages:
- High efficiency in the removal of heavy metals.
- Protection of downstream membrane systems against damage and contamination.
- Compliance with legal discharge limits for heavy metals.
Photo: Our CP system ALMA CHEM MCW with sludge dewatering through our chamber filter press
2. biofiltration
Why biofiltration is a key technology:
Biofiltration systems are ideal for treating organically contaminated wastewater, for example from the food industry, chemical industry or paper industry. They reduce the organic load and prevent biofouling in downstream reverse osmosis systems.
Technology and functionality:
- Microbial degradation: Microorganisms settle on bioactive filter media (e.g. sand, plastic granulate, activated carbon) and degrade organic compounds such as hydrocarbons, fats and proteins.
- Aeration: Oxygen is introduced into the filters to promote the activity of aerobic microorganisms.
- Particle filtration: In addition to biological activity, biofiltration also removes suspended solids and solids mechanically.
Areas of application:
- Pre-treatment for reverse osmosis systems: Reduction of organic loads to minimize fouling and clogging of the membranes.
- Industrial applications: Treatment of process water in the food and beverage industry and for organically contaminated waste water in the chemical industry.
Advantages:
- Sustainable, chemical-free removal of organic compounds.
- Extended service life and improved efficiency of downstream membrane filtration.
- Flexibility in adapting to different wastewater compositions.
Photo: Our ALMA BioFil Compact biofiltration system for treating wastewater upstream of reverse osmosis systems
3. membrane systems (reverse osmosis)
Why reverse osmosis is a key technology:
Reverse osmosis (RO) is the backbone of water recycling. It removes almost all dissolved salts, organic pollutants, trace substances, PFAS (perfluorinated and polyfluorinated alkyl substances) and other micropollutants and enables water to be reused in industrial processes.
Technology and functionality:
- High pressure process: Water is pressed through semi-permeable membranes under high pressure (10-70 bar).
- Retention of impurities: Dissolved substances such as salts, heavy metals, organic molecules and micropollutants remain on the concentrate side, while purified water (permeate) passes through the membrane.
- Modular design: Systems can be scaled according to requirements and combined with pre- and post-treatment stages.
Areas of application:
- Water recycling: recovery of process water in the electronics, chemical and food industries, for example.
- Removal of trace substances: Reduction of PFAS, drug residues and pesticides in industrial wastewater.
- Production of pure and ultrapure water: supplying cooling and boiler systems with demineralized water.
Advantages:
- Removes up to 99 % of dissolved substances and pollutants.
- Allows waste water to be reused and reduces the need for fresh water.
- Flexibility and high scalability for a wide range of requirements.
Photo: Our ALMA OSMO reverse osmosis system for removing PFAS, installed in the ALMA MODUL technical room container
Requirements for water treatment plants
Quality standards:
- Drinking water quality: Requires the complete removal of germs, organic substances and potential pollutants.
- Process water: Depending on the application, low salt content, freedom from hardness or chemical stability are required.
- Wastewater: Compliance with legal discharge limits as defined in the Water Framework Directive or local regulations.
Flexibility and scalability:
- Modular design for adaptation to changing raw water qualities and production requirements.
- Integration of monitoring systems for monitoring parameters such as pH value, conductivity, TOC and COD.
Challenges and the future of water treatment
Increasing demands on environmental standards, resource conservation and efficiency are driving the development of modern water treatment technologies. Companies are faced with the challenge of improving their water balances and complying with legal requirements at the same time.
- Sustainability: The integration of water recycling and resource-saving processes is becoming the norm.
- Technological developments: Advanced Oxidation Processes (AOPs), smart monitoring systems and modular systems enable more flexible and efficient water treatment.
- Regulatory requirements: Compliance with strict regulations, particularly with regard to micropollutants such as PFAS, is becoming increasingly relevant.
Conclusion
Water treatment is essential for sustainable and efficient industrial production. It ensures the protection of plants, compliance with legal regulations and the minimization of the ecological footprint. Whether for process water, cooling water, boiler water or water recycling - the choice of the right technologies, adapted to the specific requirements, is crucial for the success of modern industrial plants. The continuous development of technologies and their integration into existing processes secure the future of water treatment and enable the responsible use of resources.
For further information on our products, please feel free to contact us at any time!
