Lack of access to clean water in developing countries continues to be one of the highest development priorities. Currently, 1.1 billion people lack access to improved water quality. Diseases related to inadequate water cause an estimated 80% of all sickness in the developing world, resulting in 5 million deaths occurring each year of which 90% are children. In the vast majority of cases encountered within the developing world, the poor quality of water is assigned to microbial causes. The primary source of contamination is human feaces; its presence is typically the result of a combination of both poor waste disposal practices and poor post-defecatory personal hygiene practices. Inspite of the numerous projects policies and the governmental and private investments, global access to improved drinking water is far from being reached. Lots of challenges persist and impede water development. Traditional western-style municipal water treatment plants for instance, are impractical for many of the populations at risk because of the high costs of construction. There are also the problems associated with system maintenance and water quality monitoring.

Affordable Household Water Treatment Systems (HWTS) constructed from locally available materials are considered appropriate alternatives to the high-cost municipal systems. Low-cost, simple technologies at the household level are capable of dramatically improving the microbiological quality of household water and reducing the risk of infectious diseases and deaths in populations of all ages in the developed and developing world. HWTS have the potential to offer immediate benefit to populations at risk. Of course the long-term goal must be the provision of access to safe, piped water supplies.

The present study was focused on investigating and evaluating four HWTS, namely, electrolysis of water, filtration with biosand filter, coagulation with Moringa stenopetala seeds powder and filtration with colloidal silver- impregnated clay pots, with regard to their efficiency in improving the bacteriological quality of drinking water. Three indicator bacteria, namely; Escherichia coli, Streptococcus fecalis and Pseudomonas putida were used in this study for inoculation of the water samples. They were added at 3 log units, which represent concentrations comparable to environmental concentrations of surface waters used for drinking water production. The bacterial removal efficiency of the four different methods was carried out by applying Spread Plate count of the CFU for the bacteria before and after application of the disinfectant methods. The methods were also investigated on water of different turbidity levels.

All the four methods were observed to improve the bacteriological quality of drinking water. Electrolysis of water with the ecodis apparatus was found to be an effective method for treatment of drinking water. The efficiency was found to rely on the current at which the apparatus operated. Applying an electric current exceeding 0.5A resulted in 3 log bacterial removal (at least 99%). The biosand filter used for water filtration demonstrated an increasing trend in the efficiency for bacterial removal with time. Filtration in the fourth week of the test led to an enhanced bacterial removal of 97%. Treating filtered water samples having a turbidity of 5 NTU with Moringa stenopetala seed powder using dosages of 100, 200 and 300 mg/L did not result in considerable bacterial removal, unlike the treatment imposed on the water samples of 28 NTU. The latter led to 3 log bacterial removal both at a dosage of 300 mg/L for 1.0 h shaking and 200 mg/L for 1.5 h shaking (at least 99%). Clay pots gave 3 log bacterial removal upon coating with 100 ppm of colloidal silver. Increasing the amount of colloidal silver applied to the surfaces of the pots resulted into increased bacterial removal efficiency.

All the methods except biosand filters produced water meeting the WHO bacteriological standards set in the Guidelines for Drinking Water (2004).

Considering the close association between water treatment and water storage, tests were carried out to investigate the contribution of the materials of storage vessels on the fate of bacteria during storage. The tests were performed at 25oC and 37oC. The results showed clay as the best storage material in comparison with polyethylene, polypropylene and stainless steel. These findings however, only hold for short-term use of the clay pots.


Auteur: Amel Abdou Hassan Mohamed
Herkomst: CMS, UGent
Referentie: Referentie