512 equalization equalization is performed to ensure

  • No School
  • AA 1
  • 121

This preview shows page 75 - 78 out of 121 pages.

5.1.2 Equalization Equalization is performed to ensure the uniform distribution of pH, pollution load and temperature. It is carried out by air agitation or mechanical mixing. It helps to Table 7 Discharge standards for textile industry in the USA (Wang et al. 2011 ) Serial number Parameters Maximum load (kg/t of fabric) 1. BOD 5 22.4 2. COD 163 3. TSS 35.2 4 S 0.28 5 Phenol 0.14 6. pH 6.0 9.0 Nanochemicals and Ef fl uent Treatment in Textile Industries 69
Image of page 75
fi x a single separation process as conditions remain a constant. The hydraulic retention time for this is around 8 h. 5.1.3 Floatation Equalization is followed by the fl oatation process. In this process three phases are established of liquid, gas and solid due to the production of microbubbles. Compressed air is usually passed in through the mixture which causes smaller particles to attach to it due to surface tension, buoyancy of the rising bubble hydrostatic pressure. Due to lower density compared to water, these bubbles rise, helping to get rid of tiny fi bres and oil particles. 5.1.4 Coagulation, Flocculation and Settling After all these processes are complete, coagulating chemicals such as alum, ferrous sulphate, ferric chloride and lime are added to the system in a process called fl ash mixing. The colloidal particles which were not separated during settling and fl oatation are separated during this process. Colloidal particles usually carry a charge, either positive or negative and the addition of a coagulating agent exposes the charged colloid to an oppositely charged agent which leads to coagulation and further settling due to increase in density. Formation of fl ocs (aggregates) increases the density further and helps in rapid settling. This mixture is then processed through the fl occulator and further the coagulated mass is separated by settling in settling tanks. A clari fl occulator helps to remove sludge content by some amount of adsorption. Choosing the right coagulant depends on the kind of pollutants present in the ef fl uent stream after equalization. Coagulation or fl occulation helps in removal of suspended solids and to a certain extent helps in removal of colour from the exit steam as well. They also help reduce the BOD and COD (Verma et al. 2012 ). 5.2 Biological Treatment Biological treatment helps remove dissolved matter and is more ef fi cient than physicochemical treatment. The ratio between organic load and the biomass present in the reaction tank, the reactor temperature and oxygen concentration determines the removal ef fi ciency. Aeration leads to a suspension effect, but it is important to ensure that a mixing energy that can destroy the fl ocks is not reached, because it can inhibit the settling. The biomass concentration usually is between a range of 2500 4500 mg/l and oxygen content is found to be around 2 mg/l. Based on the oxygen availability, biological treatment can be classi fi ed into two main types: aerobic and anaerobic 70 P. Senthil Kumar et al.
Image of page 76
treatment methods. Aerobic biological treatment has higher ef fi ciency and wider
Image of page 77
Image of page 78

You've reached the end of your free preview.

Want to read all 121 pages?

  • Fall '19
  • N. Gokarneshan

What students are saying

  • Left Quote Icon

    As a current student on this bumpy collegiate pathway, I stumbled upon Course Hero, where I can find study resources for nearly all my courses, get online help from tutors 24/7, and even share my old projects, papers, and lecture notes with other students.

    Student Picture

    Kiran Temple University Fox School of Business ‘17, Course Hero Intern

  • Left Quote Icon

    I cannot even describe how much Course Hero helped me this summer. It’s truly become something I can always rely on and help me. In the end, I was not only able to survive summer classes, but I was able to thrive thanks to Course Hero.

    Student Picture

    Dana University of Pennsylvania ‘17, Course Hero Intern

  • Left Quote Icon

    The ability to access any university’s resources through Course Hero proved invaluable in my case. I was behind on Tulane coursework and actually used UCLA’s materials to help me move forward and get everything together on time.

    Student Picture

    Jill Tulane University ‘16, Course Hero Intern

Stuck? We have tutors online 24/7 who can help you get unstuck.
A+ icon
Ask Expert Tutors You can ask You can ask You can ask (will expire )
Answers in as fast as 15 minutes
A+ icon
Ask Expert Tutors