What is eWQMS?

Emanti Management's Water Quality Management System (eWQMS) can be used to guide the tracking, reviewing and improving of water quality.

Colour

Colour in water is generally attributed to the presence of naturally occurring organic matter. Excess colour in water is aesthetically unacceptable to consumers.

Effect and possible implications of failure

  • Aesthetic

Although no health affects are noted, high levels of colour are generally unacceptable to consumers (not aesthetically pleasing). This could lead to consumers rejecting the water and stating that it is of poor quality.

SANS 241 Standards

  • SANS 241 Table 2 (Physical, organoleptic and chemical requirements) Column 3, Class I (recommended operational limit): <20 mg/L Pt
  • SANS 241 Table 2 (Physical, organoleptic and chemical requirements) Column 4, Class II (max. allowable for limit duration): 20 - 50 mg/L Pt
  • SANS 241 Table 2 (Physical, organoleptic and chemical requirements) Column 5, Class II water consumption period, max: No Limit

Possible reason/s for failure

  • Source water has high colour (e.g. surface water in constant contact with leaves/branches, water is turbid)
  • No colour removal process at the treatment plant (e.g. no coagulation/flocculation, no oxidation)
  • No chemicals for colour removal (e.g. coagulants/flocculants not available)
  • Incorrect/inappropriate chemicals for colour removal (e.g. chemicals used not suitable for water type)
  • Poor process control (e.g. ineffective chemical dosages, no pH adjustment, no monitoring and remedial intervention, no jar tests to optimise chemical dosages, problem with process control/SCADA system)
  • Contamination (e.g. from pipe breaks and bursts, from repairs to network, infiltration or seepage)
  • Lack of maintenance (e.g. flocculation channels/sedimentation tanks not cleaned/de-sludged, reservoirs and pipes not cleaned/flushed, remove foreign objects from open reservoirs)
  • Poor design (e.g. poor mixing, insufficient settling time, open reservoirs)
  • Sabotage/vandalism

Electrical Conductivity

Electrical Conductivity (EC) is the measure of the ease with which water conducts electricity and gives an indication of the total dissolved salt (TDS) content of the water.

Effect and possible implications of failure

  • Aesthetic

Adverse health effects may include disturbance of salt and water balance in infants, heart patients, individuals with high blood pressure, and renal disease. Aesthetic effects include a salty taste to the water (if conductivity > 150 mS/m) while water with conductivity > 300 mS/m does not slake thirst.

SANS 241 Standards

  • SANS 241 Table 2 (Physical, organoleptic and chemical requirements) Column 3, Class I (recommended operational limit): <150 mS/m
  • SANS 241 Table 2 (Physical, organoleptic and chemical requirements) Column 4, Class II (max. allowable for limit duration): 150 - 370 mS/m
  • SANS 241 Table 2 (Physical, organoleptic and chemical requirements) Column 5, Class II water consumption period, max: 7 years

Possible reason/s for failure

  • Source water has high salt content (e.g. groundwater source has natural high salinity, no source protection, sea water infiltration at coast)
  • Treatment plant cannot reduce salt content (e.g. no reverse osmosis, no electrodialysis, no distillation, no ion exchange)
  • Membranes/resins require replacement (e.g. membrane life exhausted, breakthrough achieved)
  • Poor process control (e.g. no monitoring and remedial intervention, problem with process control/SCADA system)
  • Contamination (e.g. infiltration or seepage from industry, sea water)
  • Lack of maintenance (e.g. ineffective cleaning of membranes)
  • Poor design (e.g. inappropriate treatment system)
  • Sabotage/vandalism

Dissolved Solids

Dissolved solids is a measure of the total dissolved salt (TDS) content of the water and it also provides an indication of the conductivity of the water (the ease with which water conducts electricity).

Effect and possible implications of failure

  • Aesthetic

Adverse health effects may include disturbance of salt and water balance in infants, heart patients, individuals with high blood pressure, and renal disease. Aesthetic effects of waters with high dissolved solids include a salty taste to the water and the inability to slake thirst.

SANS 241 Standards

  • SANS 241 Table 2 (Physical, organoleptic and chemical requirements) Column 3, Class I (recommended operational limit): <1000 mg/L
  • SANS 241 Table 2 (Physical, organoleptic and chemical requirements) Column 4, Class II (max. allowable for limit duration): 1000 - 2400 mg/L
  • SANS 241 Table 2 (Physical, organoleptic and chemical requirements) Column 5, Class II water consumption period, max: 7 years

Possible reason/s for failure

  • Source water has high salt content (e.g. groundwater source has natural high salinity, no source protection, sea water infiltration at coast)
  • Treatment plant cannot reduce salt content (e.g. no reverse osmosis, no electrodialysis, no distillation, no ion exchange)
  • Membranes/resins require replacement (e.g. membrane life exhausted, breakthrough achieved)
  • Poor process control (e.g. no monitoring and remedial intervention, problem with process control/SCADA system)
  • Contamination (e.g. infiltration or seepage from industry, sea water)
  • Lack of maintenance (e.g. ineffective cleaning of membranes)
  • Poor design (e.g. inappropriate treatment system)
  • Sabotage/vandalism

Odour

Drinking water should not have an objectionable odour to consumers. Decaying vegetation and metabolites of microbiota are probably the largest sources of odour (and taste) problems in surface water. The organisms most often linked to odour (and taste) concerns are Actinomycetes and blue-green algae, which form the metabolites geosmin and 2-methylisoborneol. In addition to the above, unpleasant hydrogen sulphide odours can occur when there is a deficiency of oxygen in deeper water layers in storage (result of anaerobic bacterial activity). It is also important to note that many other compounds can lead to odour (and taste) problems.

Effect and possible implications of failure

  • Aesthetic

The compounds geosmin and 2-methylisoborneol cause an earthy-musty odour in water supplies. The presence of hydrogen sulphide will impart a highly unpleasant odour (rotten eggs). The presence of undesirable odour in water supplies can lead to rejection thereof, which could result in the use of less safe sources. In addition, as many compounds may impart an odour to water, undesirable odours may indicate the presence of toxic organic substances.

SANS 241 Standards

  • SANS 241 Table 2 (Physical, organoleptic and chemical requirements) Column 3, Class I (recommended operational limit): <5 TON
  • SANS 241 Table 2 (Physical, organoleptic and chemical requirements) Column 4, Class II (max. allowable for limit duration): 5 - 10 TON
  • SANS 241 Table 2 (Physical, organoleptic and chemical requirements) Column 5, Class II water consumption period, max: No limit

Possible reason/s for failure

  • Source water has high organic content (e.g. naturally occuring, industrial activities or sewage pollution)
  • No odour causing compound removal process at the treatment plant (e.g. no oxidation (ozone, hydrogen peroxide, UV radiation), no activated carbon (powdered or granular), no combination of oxidation/adsorption, no aeration)
  • No chemicals for odour causing compound removal (e.g. oxidants not available)
  • Incorrect/inappropriate chemicals for odour causing compound removal (e.g. chemicals used not suitable for water type)
  • Poor process control (e.g. ineffective chemical dosages, no monitoring and remedial intervention, problem with process control/SCADA system)
  • Contamination (e.g. infiltration or seepage from sewage system into distribution network)
  • Lack of maintenance (e.g. activated carbon bed exhausted, flocculation channels/sedimentation tanks not cleaned/de-sludged)
  • Poor design (e.g. poor mixing, insufficient settling time)
  • Sabotage/vandalism

pH value

The pH of a solution is given by the expression: pH = -log10[H+], where [H+] is the hydrogen ion concentration. At pH less than 7, water is acidic, while at pH greater than 7 water is alkaline.

Effect and possible implications of failure

  • Aesthetic
  • Operational

A direct relationship between the pH of drinking water and human health effects is difficult, if not impossible to establish since pH is very closely associated with other aspects of water quality. The taste of water, its corrosivity and the solubility and speciation of metal ions are all influenced by pH. At low pH, water may taste sour, while at high pH water tastes bitter or soapy. At low pH, corrosion of metals and aggression of cement concrete is likely. Likewise at high pH, scale formation is likely. To minimise such effects, it is recommended that optimium pH levels are maintained.

SANS 241 Standards

  • SANS 241 Table 2 (Physical, organoleptic and chemical requirements) Column 3, Class I (recommended operational limit): 5.0 - 9.5 pH units
  • SANS 241 Table 2 (Physical, organoleptic and chemical requirements) Column 4, Class II (max. allowable for limit duration): 4.0 - 10.0 pH units
  • SANS 241 Table 2 (Physical, organoleptic and chemical requirements) Column 5, Class II water consumption period, max: No limit

Possible reason/s for failure

  • Source water has low or high pH (e.g. source water is soft and acidic or hard)
  • No stabilisation/pH adjustment process at water treatment plant (e.g. no lime dosing equipment, no limestone contactors)
  • No chemicals for stabilisation/pH adjustment (e.g. lime not available)
  • Incorrect/inappropriate chemicals for stabilisation (e.g. chemicals used not suitable for water type)
  • Poor process control (e.g. ineffective chemical dosages, inconsistent dosing, no monitoring and remedial intervention, no jar tests to optimise chemical dosages, problem with process control/SCADA system)
  • Contamination (e.g. dissolution of calcite from new cement concrete pipes, infiltration or seepage from other water sources)
  • Lack of maintenance (e.g. blocked lime dosers/limestone contactors)
  • Poor design (e.g. inappropriate treatment system, dead ends in distribution network)
  • Sabotage/vandalism

Taste

Drinking water should not have an objectionable taste to consumers. Decaying vegetation and metabolites of microbiota are probably the largest sources of taste (and odour) problems in surface water. The organisms most often linked to taste (and odour) concerns are Actinomycetes and blue-green algae, which form the metabolites geosmin and 2-methylisoborneol. In addition, it is also important to note that many other compounds can lead to taste (and odour) problems.

Effect and possible implications of failure

  • Aesthetic

The compounds geosmin and 2-methylisoborneol cause an earthy-musty odour in water supplies and could make the water taste unpleasant. The presence of undesirable taste in water supplies can lead to rejection thereof, which could result in the use of less safe sources. In addition, as many compounds may impart a taste to water, undesirable tastes may indicate the presence of toxic organic substances.

SANS 241 Standards

  • SANS 241 Table 2 (Physical, organoleptic and chemical requirements) Column 3, Class I (recommended operational limit): <5 FTN
  • SANS 241 Table 2 (Physical, organoleptic and chemical requirements) Column 4, Class II (max. allowable for limit duration): 5 - 10 FTN
  • SANS 241 Table 2 (Physical, organoleptic and chemical requirements) Column 5, Class II water consumption period, max: No limit

Possible reason/s for failure

  • Source water has high organic content (e.g. naturally occuring, industrial activities or sewage pollution)
  • No odour causing compound removal process at the treatment plant (e.g. no oxidation (ozone, hydrogen peroxide, UV radiation), no activated carbon (powdered or granular), no combination of oxidation/adsorption, no aeration)
  • No chemicals for odour causing compound removal (e.g. oxidants not available)
  • Incorrect/inappropriate chemicals for odour causing compound removal (e.g. chemicals used not suitable for water type)
  • Poor process control (e.g. ineffective chemical dosages, no monitoring and remedial intervention, problem with process control/SCADA system)
  • Contamination (e.g. infiltration or seepage from sewage system into distribution network)
  • Lack of maintenance (e.g. activated carbon bed exhausted, flocculation channels/sedimentation tanks not cleaned/de-sludged)
  • Poor design (e.g. poor mixing, insufficient settling time)
  • Sabotage/vandalism

Turbidity

The turbidity is a measure of the suspended particles or degree of cloudiness of a water.

Effect and possible implications of failure

  • Aesthetic
  • Operational
  • Indirect health

Although the consumption of turbid water per se does not have any direct health effects, high turbidities imply a high concentration of suspended particles. These particles can shield bacteria and other micro-organisms from the disinfecting properties of, for example chlorine, resulting in ineffective disinfection.

SANS 241 Standards

  • SANS 241 Table 2 (Physical, organoleptic and chemical requirements) Column 3, Class I (recommended operational limit): <1 NTU
  • SANS 241 Table 2 (Physical, organoleptic and chemical requirements) Column 4, Class II (max. allowable for limit duration): 1 - 5 NTU
  • SANS 241 Table 2 (Physical, organoleptic and chemical requirements) Column 5, Class II water consumption period, max: No limit

Possible reason/s for failure

  • No filtration at the treatment plant (e.g. no slow sand or rapid filters)
  • Poor process control (e.g. inappropriate filter runs, no monitoring and remedial intervention, problem with process control/SCADA system)
  • Contamination (e.g. from pipe breaks and bursts, from repairs to network, infiltration or seepage)
  • Lack of maintenance (e.g. filters not backwashed, reservoirs and pipes not cleaned/flushed, foreign objects not removed from open reservoirs)
  • Poor design (e.g. inappropriate filter for water type and quality, open reservoirs, dead ends in network)
  • Sabotage/vandalism

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