Water/wastewater treatment

  1. Industrial and communal wastewater treatment plants

    For the treatment of wastewater from viscose, cellulose and paper production.

    • BOD degradation > 99 % 
    • COD degradation 92 % 
    • Biological wastewater treatment methods 
    • Removal of zinc by precipitation

    Method

    The process is performed in various steps: Pre-purification, neutralization, biological wastewater treatment stages I and II and flocculation filtration. 
After leaving the production plant, the wastewater is fed through a mechanical screen unit and is then neutralized. The neutralized wastewater is pumped into several pre-clarification tanks where solids are removed by sedimentation. In the pre-clarifiers, zinc is removed by precipitation by means of a specially devised neutralization and flocculation method.
    A number of chemicals are added to the wastewater, which is then pumped from the pre-clarifiers to the aeration tanks where oxygen is injected and mixed with the biological floc (activated sludge, first biological stage). During this process, easily decomposable compounds are digested by bacteria.
    In the subsequent step, the sludge is removed from the liquid phase and returned to the aeration tank for subsequent dewatering in a double-belt dewatering press.
    In the subsequent step, the sludge is removed from the liquid phase and returned to the aeration tank for subsequent dewatering in a double-belt dewatering press. 

    The liquor is then fed to the second biological stage where it undergoes similar processes as in the first biological stage but with a separate sludge system. 
Subsequently, the water is pumped through flocculation filters and released into a natural waterway. These filters consist of several layers of graded sand and remove all solids from the water.

  2. Batch and continuous-flow treatment plants

    For the processes described below, we offer two chemical-physical wastewater treatment methods, which are relevant for the choice of the subsequent treatment of the water.

    For the treatment of production wastewater, we offer:

    • Method A: Batch treatment 
    • Method B: Continuous-flow treatment

    Method A: Batch treatment

    Batch treatment has recently become more popular, as it is generally seen as the method of greater operational safety. The process is performed in several stages, whereby each stage can be closely monitored. The treatment can for example be performed in the following stages:
    Alkalization, acidification, neutralization and pH adjustment with bases and acids for subsequent processing.
    
If the required pH is reached, the batch is transferred to the next stage, depending on the treatment task.

    The number of treatment stages depends on the actual treatment requirements. At Lenzing Technik LT, we work together with the customer in selecting the treatment method and most effective treatment process.

    Method B: Continuous-flow treatment

    Although batch treatment has become more important, not least due to operational improvements as regards washing technologies and cycle control, there are many industrial applications where wastewater is preferably treated in a continuous-flow process.
    
For wastewater discharges of > 30 m³ per shift, batch treatment is not economical due to the required equipment and tank capacities, and continuous-flow treatment is the only viable option. With this method, the wastewater is treated in a continuous process, combining neutralization, oxidation, solids sedimentation, etc. LT optimizes the process by incorporating advanced process monitoring equipment that offers added safety.

  3. Neutralisation plants

    Neutralization of wastewater is one of the key tasks in effective wastewater treatment. The pH value is a measure of the acidity or basicity of an aqueous solution. The higher the concentration of hydrogen ions (H+) in a solution, the lower its pH, and the more acidic the liquid. By law, the pH of treated wastewater to be discharged must be within certain limits, normally between pH 6.5 and 9.5. In all cases, the actual requirements must be discussed with local authorities.
     
    For the various applications that require neutralization, LT offers tailor-made solutions for the treatment of:

    • Washwater from cleaning units
    • Regeneration agents from ion exchangers
    • Washwater from industrial washing processes
    • Washwater from tank cleaning
    • Effluents from preliminary treatment plants 
    • Wet-chemical treatment of wastewater
    • Etc.
  4. Oxidation and reduction plants for detoxification

    Toxic compounds in wastewater must be converted into substances that are not harmful to organism and the environment.

    By adjusting the pH of the wastewater and adding specific chemicals, pollutants are eliminated as they are converted into harmless substances or removed from the solution by precipitation. This is achieved by oxidation (where toxic compounds react chemically with oxygen to form harmless substances) and by reduction (where harmful substances are precipitated for mechanical removal). 

    The most significant detoxification reactions used for the treatment of industrial wastewater are:

    • Cyanide detoxification, especially in connection with galvanization
    • Nitrite detoxification, e.g. of grinding and hardening wastewater  
    • Chromate detoxification in hard chrome plating plants, tanneries and galvanization plants

    Detoxification systems are often only one component of the wastewater treatment process. Apart from the above oxidation and reduction plants, we also offer tailor-made designs for more specialized requirements.

  5. Precipitation, flocculation and sedimentation plants

    Unless the wastewater needs only to be neutralized, it must undergo additional treatment stages, performed in precipitation, flocculation and sedimentation units.

    In these stages, pollutants are chemically treated so that they can be mechanically removed as solids from the liquid.
    
Precipitation reactions are of huge importance in the treatment of wastewater and are used in many industrial sectors such as the following metalworking and machining applications:

    • Galvanization 
    • Metal coating of various materials 
    • Pickling and electro-polishing plants
    • Surface machining for improved corrosion resistance and enhanced surface properties
    • Chemical and physical liquid waste disposal 
    • Chemical-physical wastewater treatment plants for washwater and concentrated solutions from surface finishing processes

    Production plants that require wastewater treatment in precipitation, flocculation and sedimentation systems:

    • Galvanizing plants 
    • Hardening shops 
    • PCP production plants
    • Anodizing plants 
    • Battery production plants
    • Burnishing plants 
    • Barrel finishing plants

    Generally, the following substances must be removed from the wastewater of such plants:

    • Dissolved and undissolved heavy metals and heavy metals in complex molecules, including aluminum, arsenic, barium, lead, cadmium, chromium, iron, copper, nickel, mercury, silver, tin and zinc.  
    • Precipitation of anions such as fluorides, phosphates and sulfates.

    As the composition of wastewater changes all the time, we carry out extensive lab tests in order to determine the most suitable plant design and capacity. By choosing the right chemicals and optimizing the process, we are able to provide highly efficient plants for all requirements.
    
LT designs and manufactures components for wastewater treatment plants, including:

    • Precipitation reactors for batch and continuous-flow treatment  
    • Flocculation units, with our without reaction vessels
    • Sedimentation units such as inclined clarifiers of various design, square and circular clarifies and sludge concentrators.
  6. Filtration systems and ion exchangers

    A complete plant concept must include mechanical methods for the treatment of the sludge produced in the purification process, as well as technologies that enhance the operational safety of the system and the improvement of the wastewater discharge parameters.

    Our range of sludge dewatering systems includes conventional solutions with chamber filter presses, centrifuges and belt filter units. On request, we also provide sludge drying units.

    For the removal of suspended particles and solids that might still remain in the wastewater after treatment, LT offers filtration systems including gravel filters, continuous sand filtration, automatic backwash filters, fixed-bed filters and similar solutions (Further information: Filtration and separation technology).

    For the safe removal of dissolved heavy metals, which might remain in the liquid phase after precipitation, LT uses tried and tested selective ion exchanger technology. These systems apply extremely acidic exchange resins that act as chelates and bind heavy metals until they are released in the regeneration process. Depending on the actual metal and operating conditions, the heavy metal concentration can be reduced to less than 0.1 mg/l.

  7. Emulsion separation and absorption plants

    Emulsions are water/oil (or oil / water mixtures) that are dispersed in the liquid by adding emulators. The maximum oil content of treated wastewater to be released is limited by law. It is therefore necessary to remove these substances from the wastewater by separating the emulsion into its two components. There are a number of methods used for this purpose:

    • Chemical separation by means of acids: This method uses metal salts, alkaline precipitants and polymers. After the preliminary treatment, the separated components are fed through flotation or sedimentation plants or through systems that combine these two technologies.
    • Physical treatment of emulsions and absorbable substances: This method is particularly suitable for small wastewater volumes, and is therefore often the preferred option for the treatment of wastewater from dye plants, gluing processes and flexo printing works. Normally, adsorbents in powder form are added to the reaction vessel. The substances to be removed react with the adsorbent and can be removed from the liquid by means of standard sludge dewatering.
    • Mechanical treatment of emulsions: Where the oil phase forms a film over the aqueous phase, LT separator technology is the preferred option for removal. The emulsion can subsequently be treated with ultra-filtration (Further information: Filtration and separation technology).

    It is recommended that lab tests be carried out in order to devise the most suitable separation method.

Water/wastewater treatment

Contact
Phone: +43 7672 701-2378
Fax: +43 7672 918-2378
E-mail: umwelt-tech@lenzing.com

Brochure Environmental Technology

Brochure IM-MS Anaerobicreactor