Biological water characteristics are used to describe the presence of microbiological organisms and water-borne pathogens. Many organisms can cause illness when directly consumed by humans and animals. Micro-organisms and waterborne pathogens generally enter rivers and lakes via the release of untreated or partially treated sewage. Many waste water treatment plants located in the basin produce and discharge effluent that does not meet national discharge standards. Non-compliance may be a result of inadequate management and maintenance of sewage treatment facilities, or if the facility is operated beyond design capacity resulting in discharges of raw or partially treated sewage into the river systems.
Achieving a water quality standard that will not harm aquatic organisms, and is safe for human consumption is a challenge throughout much of the basin. This is especially true for rural areas (e.g., Momba et al. 2006, Hodgson and Manus 2006). Water borne diseases such as dysentery, cholera, typhoid, gastro-entertitis and hepatitis are the primary cause of disease and poor health in the SADC region (SADC 2009b). Bilharzia and malaria are other waterborne diseases that persist in the SADC region. Water polluted with ecoli and fecal coliform used for bathing and drinking are pricipal pathways of infection.
Typical values for water quality parameters for un-polluted and polluted water are shown in the table below.
Table: Typical values for water quality parameters.
Parameters
Units
Natural Water
Polluted Water
PH
-
6,5 – 8
4 – 10
TDS
g/m3
200
2000
Cl-
g/m3
50
600
Fe
g/m3
0,1
3
Mn
g/m3
0,05
1
EC
ms/cm
0,3
3
BOD
g/m3
2
10
COD
g/m3
10
80
DO/DOS
-
1
0,3
ammonia-N
g/m3
0,1
2,5
nitrate-N
g/m3
4
100
Source: Momba et al. 2006
GIARDIA LAMBLIA IS A PROTOZOAN PARASITE THAT CAN BE FOUND IN UNTREATED WATER AND CAUSE DIARRHOEA. SOURCE: CARR 2006
