WATER AND WASTE WATER ANALYSIS (BIOLOGICAL PARAMETERS)By: Marlisa Sau Nur Hayati Yusoff Norfarrahdilah Amir Siti Salwa Abdullah
Objectives• To compare several differences in biological characteristics of water samples• To learn the technique for evaluating water quality in term of biological parameters.
Heterotrophic Plate Count• The Heterotrophic Plate Count (HPC) is a procedure used to estimate the number of live heterotrophic bacteria that are present in a water sample.• A sample of water is put on a plate that contains nutrients that the bacteria need to survive and grow.• Each colony-forming unit represents an initial single, live bacterium that was capable of multiplying until it could be observed on the plate.• Colony count serves as a relatively easy way to measure filtration and disinfection efficiency, as well as the estimated numbers of bacteria in areas that have the potential for increased contamination.
Table 1 PLATE NUMBER OF COLONY Sample A Sample B 10¯¹ 90 colonies 33 huge colonies 10¯² One huge colony 19 colonies 10¯³ One huge colony Too many to count 10¯⁴ No colony 55 small colonies 10¯⁵ No colony 10 colonies 10¯⁶ No colony None 10¯⁷ No colony None
Calculations• Sample A1. 90/1ml x 10¯¹ = 9CFU/ml• Sample B1. 33/1ml x 10¯¹ = 3.3 CFU/ml
2. 19/1ml x 10¯² = 0.19 CFU/ml3. 55/1ml x 10¯⁴ = 3.55 x 10¯⁴ CFU/ml
Discussion• The recommend HPC levels should not exceed 500 CFU/ml.• The lower the HPC, the better the biological water quality.• The test does not specify the organisms that are detected in samples.• Micro organisms recovered through HPC tests generally include those that are part of the natural (typically non-hazardous) microbial flora found in water.
Common bacterial species detected in drinking water Bacterial Species Infectious Dose (Ingested) Pseudomonas aeruginosa 108-109 CFU Aeromonas hydrophila >1010 CFU Mycobacterium avium 104-107 CFU Xanthomonas maltophila 106-109 CFU
Precautions In order to ensure that re-growth of bacteria is kept to a minimum,• maintenance protocols• regular cleaning• temperature management• maintenance of a disinfectant residual such as chlorine
Standard Total Coliform Fermentation• The coliform group consists of several genera of bacteria belonging to the family Enterobacteriaceae.• When multiple tubes are used in the fermentation technique, results of the examination of replicate tubes and dilutions are reported in terms of the Most Probable Number (MPN) of organisms present.
• This number, based on certain probability formulas, is an estimate of the mean density of coliforms in the sample.• Coliform density provides the best assessment of water treatment effectiveness and the sanitary quality of untreated water.
Questions1. Is there any different in bacterial number for water sample from tap water, stream and selected wastewater? What does this indicate?• Yes, there is a difference in bacterial number between these water samples.• Municipal tap water should be very low if not zero for harmful bacteria.• Stream water can be low or high depending on animal activity and if there are any sewer facilities. They can be contaminated from many different sources.• Wastewater can mean two distinct things. It can be the water going into the treatment plant or the treated water coming out of the plant. Going in the bacteria level will be very high, in the millions or more. Leaving the treatment plant will be low or zero.• Bacteria levels indicate possible contamination and potential (not absolute) harms to humans
2. Why is it important to determine the number of coliform bacteria in a water source?• The total coliform test is the basic yardstick for determining a water supplys biological quality.• This test is performed frequently because of the risk that disease-causing organisms pose to health.• Any food or water sample in which this group of bacteria is found has potentially come in contact with domestic sewage, animal manure, or contaminated soil, plant, or animal material.