Assessing Water Quality from Roof Rainwater Harvesting Systems Aimed for
Potable Use: A Case Study in the Eastern Cape Province, Nomlacu Rural
Area, South Africa
Abstract
Globally, water scarcity is on the rise. South Africa has a semi-arid to
arid climate, and lack of water resources is resulting in physical water
scarcity. Eastern Cape is the second most affected and under-serviced
province with 26.1% of its population having no access to tap water.
Winnie Madikizela Mandela Local Municipality of Nomlacu currently has
73.6% municipal water supply backlog. South Africa’s primary source of
water is surface water which is of questionable quality. This gives
Rooftop Rainwater Harvesting (RRWH) systems as a water resource, great
opportunity to potentially alleviate water scarcity. RRWH collects
rainwater runoff from impermeable roof surfaces, using temporal or
permanent facilities such as buckets and storage tanks respectively.
This study aims to assess water quality obtained from a rainwater
harvesting system for potable use in Nomlacu, South Africa. Water
samples were collected from houses with zinc metal and tile roofs in
accordance to the South African National Standard (SANS 241-1:2015
Edition 2) for drinking water. According to the results obtained,
Aluminium, Colour, Conductivity @25°C, Iron, Odour, pH, Lead, Suspended
Solids, Total Dissolved Solids @105°C from both roof types remained
under allowable limits. Several studies found steel roofs to present
good water quality pertaining Colour and Turbidity. However, in this
study, Turbidity and E.coli produced non-compliant results (0.8 – 2.6
NTU) and (4 - >2420 MPN /100mL) respectively. Although
within limits, Aluminium, Colour, and Zinc present higher values on zinc
metal roof compared to tiled roofing material. This is due to the high
radiation and good heat conducting capacity of the metal. Results also
showed higher pH levels on tiled roofs (7.15 – 7.25) compared to zinc
roofs (6.27 – 6.8), which is in line with the nature of concrete.
Usually, the roof can clean itself through first flush runoff, however,
manually cleaning the roof before it starts raining and after dry season
is recommended. Trimming overhanging tree branches may minimize bird
droppings and leaves landing onto the roof. Once the water is collected,
it is imperative that disinfection solutions such as chlorine tablets be
used and that water is boiled before consumption.