Water quality tests must be conducted on rainwater if the main source of drinking water is from rainwater harvesting. Hydrogen Sulphide (H2S) strip test is one of the easy test that can be conducted by the occupants who are dependent on rainwater as the major source of drinking water.
The need for testing rainwater quality and the H2S testing method is explained in this section.
Need for Water Quality Test in Rainwater HarvestingProper maintenance of roof,the gutter, the first rain separator and the filter in a rainwater harvesting system will give crystal clear rainwater. If the water is however dirty in colour or it smells bad, then it means that the system is not kept clean. Clear water even if does not smell bad had chances to show presence of micro-biological contamination.In such situations, daily checking must be performed first month after which weekly checking is followed. The rainwater even though falls from clouds, they absorb large amount of dust and dirt from the atmosphere. This hence increase the need to check their water quality before it is used for consumption. Once it is established that the rainwater is not micro-biologically contaminated it can then be consumed directly.
Hydrogen Sulphide (H2S)Strip TestH2S Strip test is a water quality test conducted to determine the bacterial contamination of water. The testing sample is a H2S strip that is available from the market. This is the initial test conducted to determine the level of bacteria in the rainwater harvested. The test involves the following steps: 1. As shown in figure-1, the water is collected in the test bottle till the fill line. The cap is replaced once the filling is done. 2. Based on the temperature of the sample, it is kept at incubation period normally at a temperature of 250 to 370 degree Celsius. The incubation periods for different temperature ranges are tabulated below.
Table.1: The incubation period for H2S strip test sample
|Temperature Range (0C)||Incubation Period (Hours)|
Treatment of Harvested RainwaterIf the H2S strip test suggests that water has bacteria in it, it must then be treated before it can be used for drinking. The two common methods easily followed for treating contaminated rainwater are:
- Solar Disinfection of Water (SODIS)