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Chriwa Wasseraufbereitungstechnik GmbH - Technology

The wide range of the Chriwa water treatment technologies allows the individual and reliable treatment of different raw water qualities to produce waters perfectly matching the individual process requirements. Refined processes for water reclamation and state-of-the-art SCADA systems from one source allow a modern and economical water management.

Chriwa has proven know-how in the treatment processes:

Adsorption / desorption

Example: Activated carbon filtration

The aim of activated carbon filtration is the removal of toxic substances, foreign odours and foreign tastes, or a reduction of oxidative substances.

Adsorption is the accumulation of a substance on the surface of an adsorbing agent. In this process, the adsorbing agent is referred to as an 'adsorbent' and the substance being adsorbed as an 'adsorbate'. 'Adsorbate' also refers to the entire system. Adsorption is caused by van der Waals forces (weak electrostatic forces).

The reversal of adsorption – i.e. the disengagement of a substance from the surface of an adsorbing agent – is referred to as 'desorption'. Adsorption and Desorption are processes that compete with one another; in other words, they occur simultaneously.

Chriwa active carbon filtration systems are able to remove the following substances:

  • Aromatic hydrocarbons benzene, toluene, ethylbenzene and xylene
  • Mineral oil
  • Phenols
  • Foreign odours
  • Foreign tastes
  • Yeasts, fungi and fermentation products
  • Chlorine and ozone
  • Colouring

A cleaning system, which we have developed ourselves, also prevents the microbial contamination of the activated carbon used through hot water / steam sterilisation.

Ammonium removal

Generally speaking, ammonium is not harmful to humans. According to the German Drinking Water Ordinance (TrinkwV) the limit is 0.5 mg/l.

Higher ammonium concentrations can, however, lead to a growth in nitrifiers. This is also associated with heavy oxygen consumption and, in the case of incomplete nitrification, the build-up of nitrite. Due to its greater toxicity, this is assigned a considerably stricter limit of 0.1 mg/l. Autotrophic nitrifiers and their waste products can act as a source of nutrition for heterotrophic microorganisms and can therefore contribute to secondary microbial contamination of the water. When disinfecting with chlorine, the presence of ammonium leads to greater chlorine consumption and the build-up of chloramines. This points to a significantly reduced disinfectant effect and, in the event of lengthy retention times, repeated decomposition and ammonium release (THM formation).

One of the processes developed by Chriwa Wasseraufbereitungstechnik GmbH for ammonium removal is dry filtration. In this process, the water to be treated is conveyed through a filter layer using compressed air under direct current. A multi-phase flow is developed, whereby the pore space of the filter layer has both water, in the form of a thin, falling liquid film, and air flowing through it. Consequently, the lower layers are also supplied with oxygen, so that nitrification is strongly promoted here by the bacterial strains Nitrosomonas and Nitrobacter. The ammonium is converted into nitrate in this process. For nitrate significantly higher limits are permitted than for ammonium.

An additional advantage of dry filtration is that processes such as the removal of iron / manganese and foreign gases (H2S/ CH4, etc.) from the water also occur.

Ammoniom

Chlorine electrolysis

Chlorine electrolysis systems from Chriwa (AWG) produce a fresh, highly reactive disinfectant solution in the form of THM-free sodium hypochlorite or hypochlorous acid directly on site from simple base elements, such as salt, water and electricity.

Our systems are the economical and non-dangerous alternatives for disinfection with chlorine gas, commercially available chlorine bleach or other chlorine compounds.

We offer the best product for each application:

1. Membrane cell electrolysis

The ELC-M series of systems provides the opportunity to produce chlorine solutions with the highest possible degree of effectiveness with the best quality at the same time.

The ELC-MU and Stericlean series are based on membrane cell technology. However, in this process, the pure, elementary chlorine gas is obtained directly in the negative-pressure process and forms an effective, chlorinated disinfectant solution with alkaline water.

Applications: Swimming pool technology, drinking water treatment, industry and process water treatment, beverage water treatment and waste water treatment.

2. Tubular cell electrolysis

The systems of the ELC-S series are safe and impervious in operation. A lightly saline chlorine solution is produced.

The ELC-D series makes direct use of natural brine or seawater for the production of chlorine solution. An acid flushing device is integrated within the system.

Applications: Swimming pool technology, drinking water treatment, industry and process water treatment, beverage water treatment and waste water treatment.
 

3. ECA system technology

With the ECA series, a highly effective, highly reactive anolyte solution is produced with the aid of a diluted salt solution and a special ECA electrolytic cell.

Applications: Drinking water treatment, industry and process water treatment, beverage water treatment, ballast water disinfection (intern. shipping) and the food industry.

 

System output ranges from 12g Cl2/hr tov10,000 g Cl2/hr; custom rates upon request.

 

Disinfection

Disinfection represents a significant part of antiseptic operations. In technical terms, there is a distinction between disinfection and sterilisation.

Disinfection refers to a process of germ reduction by a factor of at least 105 – meaning that of an original quantity of 100,000 germs capable of reproducing (so-called colony-forming units, or 'CFUs'), no more than one survives. On the other hand, sterilisation aims for 100% decontamination.

The disinfection of waste water, drinking water or fluid media and containers and pipelines can be performed through different methods. Chriwa Wasseraufbereitungstechnik GmbH uses tried-and-tested chemical and physical methods to do this.

Processes are based on the addition of chlorine, chlorine dioxide, hydrogen peroxide, peracetic

  • Particularly common chemical acid or ozone.
  • Common physical methods are based on heating the medium or radiation with UV light.

Also applicable here is that the process is selected based on your requirements and local circumstances.

Deferrisation / demanganisation

Water changes to a rust-brown colour due to the presence of oxidised iron. Furthermore, it produces a metallic taste and can also lead to deposits and corrosion in pipelines. The German Drinking Water Ordinance (TrinkwV) prescribes a limit of 0.2 mg/litre, which must not be exceeded.

If iron and/or manganese is found in your raw water, Chriwa High Capacity Filtration is exceptionally well-suited to remove these substances. Based on our many years of experience, we have developed a system with which the best-possible filtration results can be achieved. In this process, the dissolved iron is oxidised in the water first and can then be removed in a subsequent special filtration stage. Implementation using ultra-filtration is also possible depending on the nature of the raw water.

Removal of arsenic, fluoride, radon, radium and uranium

Chriwa Wasseraufbereitungstechnik GmbH offers a wide range of different process solutions for the removal of these substances. Special and highly optimised, inert absorption substances and filter media are used for this purpose, which are permitted in drinking water and ensure the highest level of treatment quality.

Degassing / gas stripping / desorption

Unwanted foreign gases such as CO2, methane or hydrogen sulphide in water lead to interference in the biology of the filter containers, a reduction in deferrisation and demanganisation capacities, as well as to taste and smell issues in foreign water.

By using various physical and desorption methods, which are usually based on the utilisation of Henry's law, our team offers the best treatment results for the removal of foreign gases from your raw water. Amongst other things, strippers, vacuum degassing, atomisation towers, filling material sprinklers and dry filters are used for this.

Deacidification

All naturally occurring waters contain free CO2. Free, excess CO2 has an aggressive effect on metal and even concrete. The amount of excess carbon dioxide in the raw water depends on the hydrogen carbonate and calcium ion concentration, the ionic strength and the temperature of the water.

In order to remove excess carbon dioxide from your raw water, we are offering different deacidification processes.

Physical methods:

  • Flat bed ventilation
  • Sprinkling
  • Additional, various unpressurised ventilation and degassing methods

Additional chemical processes, such as filtration through special filter media or neutralisation with lyes, are also possible.

Demanganisation

Manganese possesses high biofouling potential in water distribution systems and has poisonous effects in high concentrations. It is for this reason that limits have been prescribed in this respect in the EU Drinking Water Directive and in the German Drinking Water Ordinance (TrinkwV)  of 0.05 mg/litre.

If iron and/or manganese is found in your raw water, Chriwa High Capacity Filtration is exceptionally well-suited to remove these substances. Based on our many years of experience, we have developed a system with which the best-possible filtration results can be achieved. As with the removal of iron, the manganese is first oxidised / oxidised in a filterable Mn4-flock through biofauna development. In addition, our concept offers the best results through the use of our special filtration system, ChriwaFilt Mn, which can be easily integrated into a gravel filtration system.

Decontamination / detoxification

Chriwa Wasseraufbereitungstechnik GmbH offers a wide range of different process solutions for the decontamination and detoxification of water. Special, highly optimised physical and chemical processes are used for this purpose, which ensure the highest level of treatment quality.

Filtration

For the reliable treatment of a wide range of raw waters, all common filtration technologies can be used. In this regard, our team boasts many years of experience, including in the fields of:

  • Polishing
  • Microfiltration
  • Ultrafiltration
  • Nanofiltration
  • Reverse osmosis
  • Sand filtration
  • Dry filtration

Flocculation

Finely suspended substances and colloidally dissolved impurities can be removed from water using flocculation filtration. After intensive analysis of your raw water parameters, we determine the flocculation tools required for your process. This generally involves metallic salts which, due to their electrostatic charge, are able to bind substances to them, and which can therefore be removed from the water in a subsequent filtration stage.

Amongst other things, the following substances can consequently be removed from the water:

  • Fine particles
  • Humic acids
  • Organic substances
  • Micro organisms
  • Viruses
  • Colloidally dissolved substances (e.g. clays, silicates, discolourations, etc.)

 

 

flockung

Neutral flocculants
Negatively charged flocculants
Positively charged flocculants
Oxidising flocculants

 

Gas impregnation

Our team offers extensive process solutions for the gas impregnation (e.g. with CO2, ozone, etc.) of your product water.

Ion exchange

Ion exchange is a process in which water flows through a container filled with exchanger resin. Synthetic, organic ion exchangers are predominantly polymerisation resins based on styrene or acrylate.

Ion exchange is a reversible process. The uptake of ions from the water is only possible until the functional groups are fully charged, which must then be put back into a condition where they can uptake ions again through regeneration.

Chriwa Wasseraufbereitungstechnik GmbH offers you different methods for this purpose depending on your raw water:

  • Continuous flow method
  • Counter-flow method
    • Counter-flow counter-pressure
    • Floating bed method
  • Multi-step filters
  • Mixed-bed filters (working and fine-cleaning mixed bed)


The following exchanger resins can be used for water treatment:

Cation exchanger resins:

  • Weak-acid cation exchangers are mostly polyacrylic resins, usually with carboxyl groups as functional groups. They have a largely selective effect on cations which are to be matched with the anion of the carbonic acid, meaning they are strongly dissociated in water. The main area of application is therefore also decarbonisation; i.e. the removal of hydrogen carbonates from water while releasing carbon dioxide and the retention of the hardness ions calcium and magnesium on the exchanger. These exchangers can also be used for the neutralisation of regenerating waste water.
     
  • Strong-acid cation exchangers are polystyrene resins with sulphonic acid groups as functional groups. In the Na-form they are used for the softening of water. In this process, the hardness ions are picked up from the exchanger and replaced with sodium ions. In the H-form, strongly acidic cation exchangers are used for the acidification of water. They pick up the cations from the electrolytes and give off hydrogen ions, so that free mineral acids (HCl, H2SO4 and in part HNO3) are present in the process.

Anion exchanger resins:

  • Weak-base anion exchangers are polyacrylamide or polystyrene resins with a macroporous basic framework and tertiary amino groups as functional groups.  It is not really an ion exchange that takes place on weak-base exchangers; instead they accumulate free acids – especially the strong mineral acids – during protonation of the functional groups. For this reason, it is customary to arrange a weak-base anion exchanger behind a strong-acid cation exchanger in order to remove the free mineral acids from the water.
     
  • Strong-base anion exchangers are also polystyrene or polyacrylamide resins with quaternary ammonium groups as functional groups. They can pick up the anions of both weak and strong acids, even from salts, for the exchange of hydroxide ions. In addition, there are macroporous resins here in Cl-form, which are also used as adsorbers before the cation stage for the removal of organic substances from water (so-called scavengers).

 

Membrane filtration

Membrane filtration is a physical process of separation in which, due to differential pressure, water flows through a semi-permeable membrane and is thus cleaned of dissolved substances.

The following principle applies to porous membranes:

Matter is retained when: Substance size > pore diameter

Filtration process diagram:

 filtrationsprozess

Here the process is essentially based on the filtration of water through a membrane of a certain pore size. This enables constant filtration values, even with variable feed conditions. However, diffusion and electrostatic repulsive forces in small pore diameters also contribute to the filtration process. In this process, it is possible for the water to cross through the membrane. Matter is retained based on its size and characteristics, however. Attention should also be paid to the concentration polarisation effect frequently mentioned in the sciences when treating water using membranes.

The concentration polarisation effect

Concentration polarisation diagram:

Konzentrations Polarisation

Due to the accumulation of substances, a laminar boundary layer forms at the surface of the membrane, as a result of which the particle concentration at this point is significantly greater than in the turbulent part of the inflow. As illustrated in the diagram, the concentration of particles Cp of the boundary layer therefore increases from Cp,0 of the turbulent part of the inflow to a maximum value Cp,max at the membrane surface. As a result, an ever-increasing resistance builds up over time to the passage of additional particles. An increase in pressure on the supply side increases the passing of water through the membrane (yield); but this also promotes and accelerates the additional build-up of a boundary layer and the resistance that comes with this.

In order to counter this effect, Chriwa Wasseraufbereitungstechnik GmbH offers an appropriate cleaning and anti-scaling system for all membrane filtration.

The Chriwa membrane process compared

Depending on pore size and the retention of certain substances, a distinction is made between micro-, ultra- and nanofiltration, as well as reverse osmosis. We can quickly determine for you which method is specially required for your process in a consultation session and through the analysis of raw water parameters.

Membrane method overview:

Memebranverfahren

Microfiltration

Mikrofiltration

Microfiltration is used mostly in the food and pharmaceutical industries. Additional application options are waste water treatment as well as use as a cleaning stage before a reverse osmosis system.

Amongst other things, the following substances can be removed from the water:

  • Zooplankton
  • Algae
  • Bacteria
  • Suspended particles

Here the filtration process is essentially based on the permeability of a porous membrane. Large particles form a filter cake on the surface (surface filtration), while smaller particles penetrate the membrane pores and are retained there due to adsorption or electrostatic attractive forces (depth filtration).

Since a Chriwa microfiltration system is used, the water is not demineralised. This means that salts remain in the water and are not held back by the membrane.

Ultrafiltration

Ultrafiltration

Ultrafiltration is mostly used in drinking water treatment and in the beverages industry.

Amongst other things, the following substances can be removed from the water:

  • Substances which can be removed from the water due to the microfiltration
  • Macromolecules
  • Viruses
  • Colloidally dissolved solids

Here the filtration process is essentially based on the permeability of a porous membrane. Large particles form a filter cake on the surface (surface filtration), while smaller particles penetrate the membrane pores and are retained there due to adsorption or electrostatic attractive forces (depth filtration). In this process, the best filtration results can be achieved with minimal pressure loss, which means the overall pressure within the system can also be kept low.

Since a Chriwa ultrafiltration system is used, the water is not demineralised. This means that salts remain in the water and are not held back by the membrane.

Nanofiltration

Nanofiltration

Nanofiltration is mostly used in the chemical, pharmaceutical, food and textile industries. Another field of application is waste water treatment.

Amongst other things, the following substances can be removed from the water:

  • Substances which can be removed from the water due to microfiltration and ultrafiltration
  • Organic substances
  • Large, multiply charged ions (bicarbonate reduction, etc.)

Here the filtration process is essentially based on electrostatic attractive forces, as well as the diffusion of the small parts through the non-porous membrane.

Reverse osmosis

Umkehrosmose

Reverse osmosis is mostly used in producing low-salt product water and boiler water treatment, brackish water and seawater treatment, as well as in water treatment for the beverage industry.

Amongst other things, the following substances can be removed from the water:

  • Substances which can be removed from the water due to micro-, ultra- and nanofiltration
  • Multiply charged ions
  • Singly charged ions

Here the filtration process is essentially based on the diffusion of the small parts through the non-porous membrane. Re-mineralisation is possible with specially selected salts or through raw water blending.

Neutralisation

Our team provides extensive process solutions for the neutralisation of alkaline and acidic fluids. Process water / waste water.

 

Oxidation

All common methods can be used for the oxidation of your raw water. This includes, in particular, physical and chemical processes, such as ventilation with atmospheric oxygen, UV radiation and using strong oxidising agents, such as potassium permanganate, chlorine, ozone and hydrogen peroxide.

 

Sedimentation

Example: Lamella separator

In a Chriwa lamella separator, substances capable of sedimentation (such as previously flocculated substances) can be removed from the water. In this process, the raw water flows through a tank in which diagonally arranged lamella packets are inserted. Here the water flows underneath into the packets and flows through them, whereby the substances sediment on the lamella themselves and flow into the collection container as sludge. This can easily be discharged through the valves attached to the underside of the separator.

Sedimentation EN

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