Undergraduate Thesis - Feasibility of Rainwater Harvesting in Paarden Island

This section aimed to identify possible sources of contamination that may be possible in Paarden Island due to industrial process that were observed. Contamination refers to any substance that would make the rainwater unfit for consumption. Sources of contamination includes solid particles that are suspended in water such as sand and clay, it also includes biological contaminants from vegetation, algae and mould. Contamination sources can also include heavy metals and other toxic chemicals that can be present due to industrial processes.

 

Assumptions

The following assumptions were made regarding the assessment of possible sources of rainwater contamination in Paarden Island:

• The sites that were observed are only used to identify possible sources of contamination and are not necessarily representative of the area.

• It was assumed that the observation of contamination sources only represented a few of the possible sources of contamination. The observations were made during a walk through the area. It was not possible to view most of the erven to observe what type of process were taking place inside the erf;

• Observations of contamination sources are mostly based on personal experience rather than actual data. It was not possible to conduct tests of the entire area of Paarden Island looking at all forms of contamination.

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Possible sources of contamination

The following are list of some contamination sources that were observed. It should be noted that the current list is not exhaustive and can be expanded to include other sources of contamination.

 

Petroleum products

Contamination from petroleum products can come in the form of petrol, diesel and various types of oils. Light and heavy vehicles were observed travelling through Paarden Island which could result in petroleum products being spilled on to road surfaces due to engine leaks as an example. Oil was also observed in surface water runoff coming from erven that belonged to petrol stations and mechanic workshops in the area as shown in figure 5-6.

 

 

 

 

 

 

 

 

 

 

 

Figure 5‑6: Petroleum based pollution on asphalt road surfaces

 

Total Phosphorus and Orthophosphate sources

High levels of phosphate could result from ground surface water runoff from the grass parks that are located within Paarden Island as shown in figure 5-7. Additional sources could include industrial and sewage waste if it is not properly handled by the sewage systems and leaks or spillages occur.

 

 

 

 

 

 

 

 

 

 

 

 

 

Figure 5‑7: Grassed areas can be a source of Phosphorus, settleable solids and other biological contaminants

 

Biological contaminants

A large number of the old roof surfaces that are present in Paarden Island have some form of biological matter growing on the roof surface. The biological matter appears to be mould that is growing on the roof surface as shown in figure 5-1 and 5-8. It is not clear what type of mould this is and a specialist should be consulted for further identification to the possible contamination risks.

 

 

 

 

 

 

 

 

 

 

 

 

Figure 5‑8: Roof surface with organic matter

 

Suspended solids

It was observed that some of the ground surface water runoff contained large amounts of suspended solids such as silt and clay which made the water appear muddy. This was usually the result of erven having gravel surfacing in their yards.

 

Another erf was observed to be producing large volumes of dust as a result of an industrial process that was being carried out. It was not clear what the constituents of this dust was but did reveal that even roof surfaces can be contaminated with dust particles from other erven.

 

Assessment of contamination sources

It is very important that when considering using the ground or roof surface rainwater that the possible sources of contamination be identified. These sources of contamination can come from a variety of sources such as biological, organic, heavy metals and other toxic chemicals. It is important to clean the collection surfaces to help reduce the contamination sources which will also result in lower spending require for treatment. The sources of contamination can also come from other erven located some distance away due to air borne contamination from dust that is blown by the wind.