Jargon
pH - a measure of the acidity of the water. Most fresh water sources have a pH of 6-8. The ocean's pH is ~8.3. A pH above 7 is considered preferable because enteric pathogens prefer a pH below 7.
Enteric Pathogen - diseases which attack the digestive system such as Typhoid and Cholera
Contaminants
| Contamination types | Contamination Agents | Comments |
| Physical | Particles and suspended solids | It is common to experience large seasional variance in quantity of particles and suspended solids. When choosing intake location, consideration of the natural features such as flood terracing should be made to optimize the placement of the intake |
| Biological | Faecal waste | Faecal contamination is detected via the methods described in Water Quality Field Testing and approprate treatment methods determined based on those results. Common diseases spreat through Faecal contaminataion include cholera and typhoid fever. |
| Algae | Algae can result in bad taste. It is difficult to remove with coagulants and can speed up deterioration of sand filters. Bankside filtration can help to avoid these problems | |
| Chemical | Minerals, soil type | High salinity (due to the presense of Sodium ions) is treated with expensive procedures such as reverse osmosis and distillation. pH (due to the presence or lack of Hydrogen ions) must also be considered as its levels influence coagulant and chlorine dosages and contact times
The pH and salinity of different sources can vary, even though the sources may be in a close proximity. pH is an important factor where treatment involves the addition of coagulants (alum etc) as the quantity to be added is influenced by pH, as is the contact time for chlorine. |
| Industrial effluents | In a number of situations industrial or agrochemical pollution can be very marked. As the removal of such contamination requires high technology solutions, it is generally not possible to reliably achieve this during an emergency without use of more expensive and complex treatment plants. A check to ensure that insect larvae and fish life flourish in the water source can provide an indication of quality, e.g. by keeping fish in the header tank.
Look for signs of agricultural activities, empty chemical sacks etc. to establish if there is a potential for chemical contamination. Rivers and streams are more likely to be “self cleansing” than ponds and lakes. |