Chapter 1 Biological Water Quality

WATER QUALITYBAA3613 environmental engineering

Biological parameter

INDICATOR ORGANISM

INDICATORDESCRIPTIONTURBIDITYTurbidity refers to cloudiness of water. Turbidity has no health effects, but can interfere with disinfection and provide a medium for microbial growth. Turbidity may indicate the presence of disease-causing organisms. These organisms include bacteria, viruses, and parasites that can cause symptoms such as nausea, cramps, diarrhea and associated headaches.Total coliformsColiforms are bacteria that are naturally present in the environment and used as an indicator that other, potentially harmful, bacteria may be present. Coliforms found in more samples than allowed is a warning of potential problems.Fecal coliform and Escherichia coli (E. coli)Fecal coliform and E. coli are bacteria whose presence indicates that water may be contaminanted by human or animal wastes. Microbes in these wastes can cause short term effects, such as diarrhea, cramps, nausea, headaches, or other symptoms. They may pose a special health risk for infants, young children, and people with severely compromised immune systemsFecal indicators (Enterococci or coliphage)Fecal indicators are microbes whose presence indicates that the water may be contaminated with human or animal wastes. Coliphage are viruses that infect the bacterium E. coli. Enterococci are bacterial indicators of fecal contamination. Microbes in these wastes can cause short-term health effects, such as diarrhea, cramps, nausea, headaches, or other symptoms. They may pose a special health risk for infants, young children, some of the elderly, and people with severely compromised immune systems.

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MEASUREMENT OF BIOLOGICAL PARAMETERS

1.MPNMPN = no of positive tubes x 100(mL of samples in negative tubes x mL of samples in all tubes)1/2

Example 1

A bacterial analysis for a surface water yielded the following results for the standard confirmed test for total coliform. Determine the coliform density (MPN) using the MPN tables and the Thomas equation.

2.MFM

Example 2 Assume that filtration of volumes 75, 25, 10, 3 and 1 mL produced FC colony counts of 210, 89, 35, 11 and 5, respectively. What is the FC density for the sample?

SolutionSelect the membrane filter with the number of colonies in the acceptable range. The acceptable range for TC is 20-80 TC colonies and no more than 200 colonies of all types per membrane. Sample quantities producing MF counts of 20-60 colonies of FC or FS are desired. The MF with 35 FC colonies is the best MF for counting. Thus, the density is

3.P-A test

Presence of E-coliPresence of Total coliform

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