WASTE WATER TREATMENT
Effluent waste water from an industrial facility may carry
a broad and variable range of contaminants, including BOD, COD,
color & odor phenols, cyanides, sanitary waste and a host of complex chemicals. Ozone, in combination with other physical, chemical or biological processes, has the potential to treat complex industrial wastes due to its strong oxidative nature. In combination with medium pressure UV, Ozone exhibits the power of advanced oxidation for TOC reduction, as well as destruction of organics. Potential industries that can benefit from ozone include pharmaceuticals, textiles, automotive, foundry, etc.

 

The location of ozone use in WWT will determine the goal of treatment. A simple way to explain a classical WWT will be break up the process into:

  • 1) Preliminary treatment consisting of process such as screening
  • 2) Primary treatment including sedimentation
  • 3) Secondary treatment including activated sludge treatment and secondary     sedimentation
  • 4) Tertiary treatment including discoloration, disinfection, COD reduction etc
Ozone finds use in each of these stages of WWT. Ozone during preliminary stage is used for detoxification. Ozone at secondary stage is used for sludge reduction, and Ozone during the tertiary stage is more common and used for disinfection, micro pollutant removal, COD reduction and decoloration.The location of Ozone is dependant on the goal of ozonation.
In each of these cases the use of Ozone has been found to be very productive.

Decolourisation & Deodorization

Due to new government restrictions for the discharge of colored water and the increasing discharge costs of waste water Ozone oxidation for decoloration is becoming more and more popular. The effected industries are companies producing textiles, dyes, paper or chemicals. Additional to the very successful results in decoloration, Ozone brings further benefits like desinfection, improved BOD/COD-ratio, reduced AOX and reduction of odour. Waste water or recycling water can be treated in an environmentally-friendly way without any residuals or concentrates by using Ozone.


De toxification

Some of the more common toxic substances that are found in waste water (Industrial and Municipal too) are:

  • 1) Chemicals like cyanide , phenols and phenolic compounds,nitrites
  • 2) Pesticides and products such as Tensides ( surfactants in detergents)
  • 3) Micro pollutants such as EDC ( endocrine disrupting Compounds )

We are quite aware of toxic substances such as pesticides, phenolic compounds that has been addressed by pollution control authorities in India. However the world as woken up to a new set of compounds know as EDC.

EDCs are micro pollutants

  • Different groups of persistent micro pollutants are daily released by human activities        into the water cycle.
  • EDC´s (Endocrine Disrupting Compounds), pharmaceuticals and personal care        products are groups of emerging contaminants.
  • EDC´s are substances which impact hormone function in animals and humans
          -Natural or man made that disrupt growth, development, or reproduction.
  • Anthropogenic substances that affect the hormone balance.
  • A cause for great concern is the multiplier effect.
  • Growing concern forced detailed investigations into this topic all over the world       (Australia, Switzerland, UK, USA,..).

Disinfection

Effluents of biological treatment plants for municipal sewage still contain substances that prevent a reuse: Reasons for waste water disinfection can be removal of :

  • Fecal and coliform germs
  • Parasites and viruses
  • Biological persistant substances such as (AOX, pesticides, chlororganic substances..)
  • Colour causing substances
  • Unpleasant odour

These can be responsible for causing several water borne diseases.

Some of the international regulations for waste water disinfections are:

  • EU Bathing Water Directive (76/160 EWG)
  • WHO Guideline (2003)
  • California Waste Water Reclamation Criteria (CRWC) Title 22

COD/BOD Reduction:

The table below gives some idea of the choice of different technologies available for waste water treatment. Mostly the choice of a particular technology is governed by two criteria:

  • 1) The flow of the effluent
  • 2) The COD content
TECHNOLOGY COD
CONTENT mg/l
FLOW RATE
INCINERATION AND EVAPORATION 15000 – 100000 1M3 /hr to 10M3/hr
ANEROBIC BIOLOGICAL TREATMENT 15000 – 100000 10M3/hr to 100M3.hr
WET AIR OXIDATION 8000-50000 5M3/hr to 100M3/hr
AOP ( UV /H2O2/FENTON ) 1000-6000 0.5M3/HR TO 10M3/HR
AEROBIC BIOLOGICAL TREATMENTINCLUDING ACTIVATED SLUDGE/MBR/BIO FILTER 15 - 10000 10M3/HR-10000 M3/HR
OZONE 10 - 1200 1M3/HR TO 10000M3/HR
ELECTROLYTIC OZONE INCLUDING LBT UV SYSTEMS 0.1 - 0.7 0.5M3/HR TO 100M3/HR

From the above it can be seen that Ozone technology is not restricted due to the flow of the effluent . However the choice of this technology will entirely depend on the COD content. The choice of Ozone will depend on the goal of the treatment.


SLUDGE REDUCTION

Sludge handling costs have now become one of the main operating costs ( even up to 40-50% of the total costs of the waste water treatment ) for waste water treatment plant operators. Especially in the textile industry, major sludge formation is due to the use of flocculants for the removal of color during primary and secondary treatment. In spite of this large usage of flocculants, color removal of certain types of dyes has not been very satisfactory. The COD reduction has also not been very consistent with classical treatment. Ozone has been tried with the main goal of sludge reduction. Large amounts of Ozone are required for sludge reduction if used during primary or secondary treatment process but results have been obtained. However it is up to user to evaluate the costs associated with the use of Ozone compared to the costs incurred in handling the sludge generated by conventional treatment.

 

ARTICLES

Click to download the articles below

Waste Water Decoloration With Ozone

Ozone in Waste Water Treatment



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