World Library  
Flag as Inappropriate
Email this Article

Wastewater quality indicators

 

Wastewater quality indicators

Wastewater quality indicators are laboratory test methodologies to assess suitability of wastewater for disposal or re-use. Tests selected and desired test results vary with the intended use or discharge location. Tests measure physical, chemical, and biological characteristics of the waste water.

Contents

  • Physical characteristics 1
    • Temperature 1.1
    • Solids 1.2
  • Chemical characteristics 2
    • Hydrogen 2.1
    • Oxygen 2.2
    • Nitrogen 2.3
    • Phosphates 2.4
    • Chlorine 2.5
  • Biological characteristics 3
  • See also 4
  • References 5
  • Further reading 6
  • External links 7

Physical characteristics

Temperature

Aquatic organisms cannot survive outside of specific temperature ranges. Irrigation runoff and water cooling of power stations may elevate temperatures above the acceptable range for some species. Temperature may be measured with a calibrated thermometer.[1]

Solids

Solid material in wastewater may be dissolved, suspended, or settled. Total dissolved solids or TDS (sometimes called filterable residue) is measured as the mass of residue remaining when a measured volume of filtered water is evaporated. The mass of dried solids remaining on the filter is called total suspended solids (TSS) or nonfiltrable residue. Settleable solids are measured as the visible volume accumulated at the bottom of an Imhoff cone after water has settled for one hour.[2] Turbidity is a measure of the light scattering ability of suspended matter in the water.[3] Salinity measures water density or conductivity changes caused by dissolved materials.[4]

Chemical characteristics

Virtually any chemical may be found in water, but routine testing is commonly limited to a few chemical elements of unique significance.

Hydrogen

Water ionizes into hydronium (H3O) cations and hydroxyl (OH) anions. The concentration of ionized hydrogen (as protonated water) is expressed as pH.[5]

Oxygen

Most aquatic habitats are occupied by

  • Discussion of BOD and COD (use BOD as the keyword in the pdf search function)
  • Discussion of BOD and COD (use BOD as the keyword in the pdf search function)
  • More about COD and BOD (scroll to section on "Advantage of using COD over BOD")

External links

  • Tchobanoglous, M, Mannarino, F L, & Stensel, H D (2003). Wastewater Engineering (Treatment Disposal Reuse) / Metcalf & Eddy, Inc, 4th Edition, McGraw-Hill Book Company. ISBN 0-07-041878-0.
  • Beychok, Milton R. (1967). Aqueous Wastes from Petroleum and Petrochemical Plants, 1st Edition, John Wiley & Sons, LCCN 67019834.

Further reading

  1. ^ Franson, Mary Ann Standard Methods for the Examination of Water and Wastewater 14th edition (1975) APHA, AWWA & WPCF ISBN 0-87553-078-8 pp.125-126
  2. ^ Franson, Mary Ann Standard Methods for the Examination of Water and Wastewater 14th edition (1975) APHA, AWWA & WPCF ISBN 0-87553-078-8 pp.89-98
  3. ^ Franson, Mary Ann Standard Methods for the Examination of Water and Wastewater 14th edition (1975) APHA, AWWA & WPCF ISBN 0-87553-078-8 pp.131-137
  4. ^ Franson, Mary Ann Standard Methods for the Examination of Water and Wastewater 14th edition (1975) APHA, AWWA & WPCF ISBN 0-87553-078-8 pp.99-100
  5. ^ Franson, Mary Ann Standard Methods for the Examination of Water and Wastewater 14th edition (1975) APHA, AWWA & WPCF ISBN 0-87553-078-8 pp.406-407
  6. ^ Goldman, Charles R. & Horne, Alexander J. Limnology (1983) McGraw-Hill ISBN 0-07-023651-8 p.111
  7. ^ Franson, Mary Ann Standard Methods for the Examination of Water and Wastewater 14th edition (1975) APHA, AWWA & WPCF ISBN 0-87553-078-8 pp.406-407
  8. ^ MacCutheon et al., 1983
  9. ^ US EPA (1984)
  10. ^ Nduka et al., 2008
  11. ^ WHO (1984)
  12. ^ Franson, Mary Ann Standard Methods for the Examination of Water and Wastewater 14th edition (1975) APHA, AWWA & WPCF ISBN 0-87553-078-8 pp.309-315
  13. ^ Franson, Mary Ann Standard Methods for the Examination of Water and Wastewater 14th edition (1975) APHA, AWWA & WPCF ISBN 0-87553-078-8 pp.685-689
  14. ^ Franson, Mary Ann Standard Methods for the Examination of Water and Wastewater 14th edition (1975) APHA, AWWA & WPCF ISBN 0-87553-078-8 pp.875-877

References

See also

[14] Water may be tested by a

Biological characteristics

Chlorine has been widely used for bleaching, as a disinfectant, and for biofouling prevention in water cooling systems. Remaining concentrations of oxidizing hypochlorous acid and hypochlorite ions may be measured as chlorine residual to estimate effectiveness of disinfection or to demonstrate safety for discharge to aquatic ecosystems.[12]

Chlorine

Phosphorus is normally low (< 1 mg/l) in clean potable water sources and usually not regulated;[10][11]

  1. No more than 0.1 mg/L for streams which do not empty into reservoirs,
  2. No more than 0.05 mg/L for streams discharging into reservoirs, and
  3. No more than 0.025 mg/L for reservoirs.[9]

The following criteria for total phosphorus were recommended by the U.S. Environmental Protection Agency.

Phosphates are not toxic to people or animals unless they are present in very high levels. Digestive problems could occur from extremely high levels of phosphate.

Phosphates enter the water ways through both non-point sources and point sources. Non-point source (NPS) pollution refers to water pollution from diffuse sources. Nonpoint source pollution can be contrasted with point source pollution, where discharges occur to a body of water at a single location. The non-point sources of phosphates include: natural decomposition of rocks and minerals, storm water runoff, agricultural runoff, erosion and sedimentation, atmospheric deposition, and direct input by animals/wildlife; whereas: point sources may include: waste water treatment plants and permitted industrial discharges. In general, the non-point source pollution typically is significantly higher than the point sources of pollution. Therefore, the key to sound management is to limit the input from both point and non-point sources of phosphate. High concentration of phosphate in water bodies is an indication of pollution and largely responsible for eutrophication.[8]

Total Phosphorus and Phosphate, PO4-3

Phosphates

[7]

Nitrogen

  • 5-day BOD and Ultimate BOD: Sections 5210B and 5210C
  • COD: Section 5220

The laboratory test procedures for determining the above oxygen demands are detailed in the following sections of the "Standard Methods For the Examination Of Water and Wastewater" available at www.standardmethods.org:

There is no generalized correlation between the 5-day BOD and the Ultimate BOD. Likewise, there is no generalized correlation between BOD and COD. It is possible to develop such correlations for a specific waste contaminant in a specific wastewater stream, but such correlations cannot be generalized for use with any other waste contaminants or wastewater streams.

There are also many different COD tests. Perhaps, the most common is the 4-hour COD.

The so-called 5-day BOD measures the amount of oxygen consumed by biochemical oxidation of waste contaminants in a 5-day period. The total amount of oxygen consumed when the biochemical reaction is allowed to proceed to completion is called the Ultimate BOD. The Ultimate BOD is too time consuming, so the 5-day BOD has almost universally been adopted as a measure of relative pollution effect.

Both the BOD and COD tests are a measure of the relative oxygen-depletion effect of a waste contaminant. Both have been widely adopted as a measure of pollution effect. The BOD test measures the oxygen demand of biodegradable pollutants whereas the COD test measures the oxygen demand of biogradable pollutants plus the oxygen demand of non-biodegradable oxidizable pollutants.

Oxidizable chemicals (such as reducing chemicals) introduced into a natural water will similarly initiate chemical reactions (such as shown above). Those chemical reactions create what is measured in the laboratory as the chemical oxygen demand (COD).

Since all natural waterways contain bacteria and nutrient, almost any waste compounds introduced into such waterways will initiate biochemical reactions (such as shown above). Those biochemical reactions create what is measured in the laboratory as the biochemical oxygen demand (BOD).

NO2 + ½ O2 → NO3
S2− + 2 O2 → SO42−

Oxygen consumption by reducing chemicals such as sulfides and nitrites is typified as follows:

Oxidizable material + bacteria + nutrient + O2 → CO2 + H2O + oxidized inorganics such as NO3 or SO4

The reaction for biochemical oxidation may be written as:

[6]

This article was sourced from Creative Commons Attribution-ShareAlike License; additional terms may apply. World Heritage Encyclopedia content is assembled from numerous content providers, Open Access Publishing, and in compliance with The Fair Access to Science and Technology Research Act (FASTR), Wikimedia Foundation, Inc., Public Library of Science, The Encyclopedia of Life, Open Book Publishers (OBP), PubMed, U.S. National Library of Medicine, National Center for Biotechnology Information, U.S. National Library of Medicine, National Institutes of Health (NIH), U.S. Department of Health & Human Services, and USA.gov, which sources content from all federal, state, local, tribal, and territorial government publication portals (.gov, .mil, .edu). Funding for USA.gov and content contributors is made possible from the U.S. Congress, E-Government Act of 2002.
 
Crowd sourced content that is contributed to World Heritage Encyclopedia is peer reviewed and edited by our editorial staff to ensure quality scholarly research articles.
 
By using this site, you agree to the Terms of Use and Privacy Policy. World Heritage Encyclopedia™ is a registered trademark of the World Public Library Association, a non-profit organization.
 


Copyright © World Library Foundation. All rights reserved. eBooks from Project Gutenberg are sponsored by the World Library Foundation,
a 501c(4) Member's Support Non-Profit Organization, and is NOT affiliated with any governmental agency or department.