Etiket Arşivleri: Membrane Filtration

Membrane Filtration of Water

Membrane Filtration of Water


Experiment No: 5 Membrane Filtration Method in “Basic methods for the Microbiological Analysis of Foods” by Prof. Dr. Osman ERKMEN. Nobel Yayınevi. Ankara 2007.


1- Dirty river water (100, 150, 200 ml)

2- Drinking water (100, 150, 200 ml)


1- Membrane Filtration Apparatus and Vacuum pump.

2- Plate Count Agar.

3- Sterile filter paper (0.45 mm)

4- Forceps


1- First Sterilize the Filtration apparatus and forceps by passing through flame.

2- Place the coarse filter between flask and funnel and close the lid. Make sure the tap of funnel is closed.

3- Take 50ml of water sample and pour into funnel without filter paper to make a trial run to wet the surface of coarse filter. Run the vacuum pump and open the tap of funnel.

4- All of the sample should be passed through coarse filter.

5- Release the funnel lock and take a sterile filter paper.

6- Open the package of filter paper at aseptic conditions and take it by using sterile forceps.

7- Place the filter paper on the coarse (green side upper) filter let it get wet and remove the green upper cover by using forceps. Filter paper should be stick on the surface of coarse filter.

8- Then place the funnel close the lock. Close the tap of funnel.

9- Add 100 ml of sample in the funnel at aseptic conditions and run the vacuum pump. Open the tap of funnel to pass the entire sample through the filter paper.

10- After all of the sample was passed, remove the funnel and remove the filter paper from the surface of coarse filter.

11- Place the filter paper on PCA at aseptic conditions. And close the lid of petri dish.

12- Repeat the procedure for 150, 200 ml of sample amounts.

13- Incubate the petri dishes in the 37°C Incubator.

14- Count formed colonies on the filter paper. Calculate number of microorganisms per ml of water sample.


Coliform Analysis in Water/ Membrane Filtration

General introduction:

Membrane  filtration  systems  are  especially  used  when  the  sample  like  drinking  water  or  fruit j uices   which  can  easily  pass through the filter  and  contain  really small  amount  of  microorganisms  less than   1 CFU/ ml.

About coliform bacteria and why do we do this test:  

Coliform   bacteria  are   present   in  the  environment  and  feces  of  all  warm-blooded  animals  and   humans.  Coliform  bacteria  are  unlikely  to  cause  illness.  However,  their  presence  in  drinking  water   indicates that  disease-causing  organisms  (pathogens)  could  be  in the  water  system.  Most  pathogens   that  can  contaminate  water  supplies  come  from  the  feces  of  humans  or  animals.  Testing  drinking   water   for   all   possible   pathogens   is   complex,   time-consuming,   and   expensive.   It   is   easy   and   inexpensive to test for coliform  bacteria.  If testing detects coliform  bacteria  in a water sample, water   services  search  for  the  source  of  contamination  and  restore  safe  drinking  water.  There  are  three   groups  of  coliform  bacteria.  Each  is  an  indicator  of  drinking  water  quality  and  each  has  a  different   level  of  risk. Total  coliform  is  a  large  collection  of  different  kinds  of  bacteria.  Fecal  coliform  are types   of  total  coliform  that  exist  in  feces.  E.  coli  is  a  subgroup  of  fecal  coliform.  Labs  test  drinking  water   samples for total  coliform.  If total  coliform  is  present, the  lab  also tests the sample for fecal  coliform   or E. coli, depending on the lab testing method.    Total  coliform  bacteria  are  common  in  the  environment  (soil  or  vegetation)  and  are  generally   harmless.  If  a  lab  detects  only  total  coliform  bacteria  in  drinking  water,  the  source  is  probably   environmental  and  fecal  contamination  is  unlikely.  However,  if  environmental  contamination  can   enter  the  system,  pathogens  could  get  in,  too.  It  is  important  to  find  and  resolve  the  source  of  the   contamination.     Fecal  coliform  bacteria  are  a  subgroup  of  total  coliform  bacteria.  They  exist  in  the  intestines  and   feces  of  people  and  animals.  The  presence  of  fecal  coliform  in  a  drinking  water  sample  often   indicates  recent fecal  contamination. That  means there  is  a  greater  risk that  pathogens  are  present.   E.  coli  is  a  subgroup  of  the  fecal  coliform  group.  Most  E.  coli  bacteria  are  harmless  and  exist  in  the   intestines  of   people  and  warm-blooded  animals.  However,  some  strains  can  cause   illness.  The   presence  of  E.  coli  in  a  drinking  water  sample  usually  indicates  recent  fecal  contamination.  That   means there is a greater risk that pathogens are present.    Note:  E.  coli  outbreaks  receive  a  lot  of  media   coverage.  A  specific  strain  of  E.  coli  bacteria   known as E. coli O157:H7 causes most of those   outbreaks.  When  a  drinking  water  sample  is   reported as  “E. coli  present,”  it does  not  mean   that   O157:H7   is   present.   However,   it   does   indicate  recent fecal  contamination.  Boiling  or   disinfecting       contaminated         drinking      water   destroys      all   forms      of   E.    coli,   including   O157:H7.