MATERIALS AND METHODS

The study took place from the November to December 2009 at the National Centre for Energy Research and Development (NCERD) University of Nigeria Nsukka. Nsukka is located at (6.9°N, 7.4°E) and 445 m above sea level. The materials used for the study were Polyethylene tephthalate (PET) bottles, activated charcoal, funnel, filter paper, kettle and heater, autoclave, incubator, oven, Electronic balance, water bath, colony counter, hot plate, bunsen burner, test tubes, petri dishes, pipettes.

Sampling
All containers were washed with 1:1 HCL. The water samples were collected from Aso River and a borehole both in Nsukka into two containers. These water sources are used by the villagers (Okoye, 2005).

Procedure
Boiling
Seven hundred and fifty milliliter each of the two water samples were measured separately into a kettle and boiled for 15 min. It was left to cool and transferred into container (Brouhard, 2009). Another 750 mL each of the two water samples were measured separately into a kettle and boiled for 1 h, 30 min. It was left to cool and transferred into container.

Solar Disinfection
Seven hundred and fifty milliliter each of the two water samples were measured separately into PET bottles, put out in the sun on top of a roof for six hours and left to cool (Anonymous, 2009).

Granular Activated Carbon (GAC) Filtration
A filter paper was folded properly into a funnel and activated charcoal was poured into it. Seven hundred and fifty milliliter each of the two water samples were separately passed through the activated charcoal and filtrate collected into a container (Turner, 2009).

Analysis
The samples were sent to the lab for analysis immediately after disinfection.

The water samples without any treatment were used as control. The control and treated samples were analysed for coliform and total viable count, using pour plate technique described by Okaka (2005) as follows:

Total Viable Count
One milliliter of the water sample in 9 mL of ¼ Ringer solution was mixed with the Nutrient Agar that has been cooled to 45 to 50°C and poured in a petridish. After incubation, the colonies that developed were counted and the concentration of the micro-organism in the original suspension was estimated. This was done in duplicates and the average taken in counts mL^-1 Okaka (2005).

Coliform Count
One milliliter of the water sample in 9 mL of ¼ Ringer solution was mixed with the MacConkey’s Agar that has been cooled to 45 to 50°C and poured in a petridish. After incubation, the colonies that developed were counted and the concentration of the micro-organism in the original suspension was estimated. This was done in duplicates and the average taken in counts mL^-1 Okaka (2005).

RESULTS

As shown in Table 1, the Total Viable Count (TVC) of the water samples were 4.50x10⁴ and 8.10x10⁴ cfu mL^-1 while for the disinfected samples, it was between 4.00x10² to 2.87x10⁵ cfu mL^-1. As shown in Table 2, the coliform count of the water samples were 1.08x10³ and 3.00x10³ cfu mL^-1 while for the disinfected samples, it was between 0.00 x10⁰ to 2.72x10⁴ cfu mL^-1. The borehole sample had higher TVC and coliform count than that of the river sample. Total viable count and coliform count of the control samples were higher than that of the boiled (for 1 h 30 min) and solar disinfected samples. But the TVC and coliform count of the filtered samples and the boiled (for 30 min) were higher than that of the control samples.

Table 1:	Results of total viable count of the water samples

Table 2:	Results of coliform count of the water samples

DISCUSSION

Total Viable Count (TVC) of the borehole sample was 8.5x10⁴ cfu mL^-1 which was higher than that of the river sample with concentration of 4.5x10⁴ cfu mL^-1. The TVC is a basic test for drinking water quality. The test gives a reading for all bacteria present. The presence of fecal coliform bacteria in aquatic environments indicates that the water has been contaminated with the fecal material of man or other animals. At the time this occurred, the source water might have been contaminated by pathogens or disease producing bacteria or viruses which can also exist in fecal material. The result obtained seems to be contrary to the fact that water from borehole is considered safer for drinking than river water. However, it should be made clear that as the river water is the main source of water for drinking in the area of study, activities such a washing and indiscriminate disposal of waste will be curbed as much as possible. As already established, contaminants can find their way into ground water through activities like industrial discharges, seepage of municipal landfills, septic tank effluents etc. (Okuo et al., 2007). The major contributions to pollution of the rivers are the households that throw their waste materials into the rivers and those whose waste water eventually end up in the river (Ogbonna et al., 2008).

The water from borehole in the process of being transferred into a water tank might have been contaminated and the seepage from drainage tanks around the area including farmlands is another possible source of contamination. Infact, many of the small premises do not have access to any disposal system other than allowing waste to soak into the ground. Industrial contaminants can also gain access to the local aquifer either via interaction with the surface water bodies or directly through infiltration (Yusuf, 2007). However, with disinfecting through boiling and solar disinfection, the TVC of the water samples reduced. But with disinfecting through granulated activated charcoal filtration, the TVC ended up increasing (Table 1).

The presence of fecal contamination is an indicator that a potential health risk exists for individuals exposed to this water. Some waterborne pathogenic diseases as a result of this include typhoid fever, viral and bacterial gastroenteritis and hepatitis A (Kotoski, 1997). The coliform count of the borehole sample which was 3x10³ cfu mL^-1 was also higher than that of the river sample which was 1.08x10³ cfu mL^-1. However, this was totally removed after boiling for 1 h 30 min and also after only solar disinfecting. The results show that the best means of water disinfection is boiling for as long as one hour thirty minutes. The water that was allowed to boil for about 15 min did not show any considerable reduction in the microbial load. Boiling may concentrate any harmful contaminants that do not vaporize as the relatively pure water vapor boils off. The solar disinfection method is also good as it completely eliminated the microorganisms. The filtration method which employed the use of activated charcoal was found to further contaminate the water from 8.10x10⁴ to 2.87x10⁵ cfu mL^-1 for the borehole sample and from 4.50x10⁴ to 2.02x10⁵ cfu mL^-1 for the river sample. The findings reveal that GAC filters, by themselves, can not remove bacteria as also stated by Johnson (2005). For surface waters with heavy levels of fecal or sewage contamination, filters should not be used as the sole means of disinfection. One rational use of filtration is to clear the water of sediment and organic debris, allowing more accurate, lower doses of halogens. Filters are mainly useful as a first step to remove parasitic and cryptosporidium organisms that have high resistance to halogens (Backer, 1995).

A benefit of all home filtration systems is that they are passive. That is, they require no electricity to filter the water and normal home water pressure is used to force the water though the filter. The only routine maintenance required is periodic replacement of the filtration element. If the filter holes are large enough, disease organisms can get through. Of special concern are viruses, which are small enough to penetrate a number of the common water filters in the market today (Anonymous, 2010). Granular Activated Carbon (GAC) are particles of carbon that have been treated to increase their surface area and increase their ability to adsorb a wide range of contaminants. The GAC filters do not require electricity, nor do they waste water. If a bed of charcoal that traps an occasional bacterium, picks up a bit of organic material and removes the chlorine from the water, one can see how these filters might become breeding grounds for the bacteria they trap (Johnson, 2005).

Comparing the results obtained from this study with the EPA (2008) standard of coliform count for drinking water, the boiled and solar disinfected water samples were okay as they were both zero as recommended. Whereas the filtered water samples were 2.72x10⁴ and 4.60x10³cfu mL^-1 for the borehole and river respectively which were even higher than 1.08x10³ and 3.00x10³cfu mL^-1 of the control samples.

Examining the cost for the different disinfection methods, many people boil with kerosene or electricity and to boil water for 1 h 30 min for disinfection will cost a lot while solar disinfection does not cost anything as the source of disinfection is the sun. However, granular activated charcoal is expensive but the method is a bit cumbersome as there is the need for a filter, careful set up and constant monitoring.

CONCLUSION

The results show that the best means of water disinfection is boiling while the use of solar could be considered a cheaper alternative although it does not eliminate completely the microbial load impeding the suitability for drinking. However, granular activated carbon filtration should be discouraged, as it increases the microbial load of water.

ACKNOWLEDGMENT

Authors are grateful to Mr. Nwankwo of National Centre of Energy Research and Development for carrying out the Coliform and Total viable count analysis.