1) Catchment | |||||||||||||
Hazardous event | Issues to consider and hazards associated with. | Raw risk | Risk rating | Basis for selecting the likelihood of the hazard and its consequences | Existing Control measure and its effectiveness | Residual risk | Risk rating | ||||||
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| Li | C | S |
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| Li | C | S | H, M or L | ||
Cattle rearing around source water | Cryptosporidium and other infectious organisms introduced into water (M) | 3 | 3 | 9 | H | Li: site visits C: cryptosporidium infection may harm human health | ECM: No | 3 | 3 | 9 | H | ||
Farming activities along the river bank | Pesticide, nitrate washed into raw water (CH) | 3 | 3 | 9 | H | Li: site visit, historical water quality showing high nitrate C: nitrate, pesticides in high concentration harms health and incompliance regulation | ECM: No | 3 | 3 | 9 | H | ||
Human defecation into the raw water | E-coli, faecal coliforms introduced into raw water (M) | 3 | 3 | 9 | H | Li: site visit, human settlement present near raw water and no toilets C: faecal microorganisms may harm the public health | ECM: No | 3 | 3 | 9 | H | ||
Dumping of refuse | Solids, debris into water (P) | 3 | 2 | 6 | M | Li: site visit and key informant interview C: debris into treatment plant system might clog filters, etc. | ECM: screens provided at intake side E: yes; no floating debris within treatment | 1 | 2 | 2 | Lo | ||
Algal blooms during hot season. | Changing color, turbidity, taste and odour, and heavy algae growth in treatment tanks (M) | 2 | 3 | 6 | M | Li: site visits key informants survey C: record shows high turbidity in the hot season affecting the aesthetics of water | ECM: No
| 2 | 3 | 6 | M | ||
People bathing in the water | Contamination of raw water (CH, M) | 3 | 3 | 9 | H | Li: site visits, historical records C: contamination from bathing | ECM: No
| 3 | 3 | 9 | H | ||
Bokoharam attack at intake side | Interrupted pumping of water, lost operators live | 2 | 3 | 6 | M | Li: key informant interview (some villages around the intake site has been attacked several times) C: terrorist may harm plant operators at the raw water intake site | ECM: soldiers deployed at intake side E: yes Several attack to villages near has been repelled with victory | 1 | 3 | 3 | Lo | ||
2) Treatment | |||||||||||||
Pre-liming pump breakdown | Temporary hardness and acidity removal not achieved | 3 | 2 | 6 | M | Li: site visits, water quality analysis. C: imbalance pH causes corrosion to pipes of treatment facilities | ECM: No
| 3 | 2 | 6 | M | ||
Natural Aeration process | Inadequate in achieving aeration benefit (CH) | 3 | 2 | 6 | M | Li: water quality analysis C: DO, odour and taste not removed (aesthetics) | ECM: No
| 3 | 2 | 6 | M | ||
Alum pipe network clogging | Interrupted coagulation treatment (P, CH, M) | 2 | 3 | 6 | M | Li: operators interview (it takes 6 months before clogging occurs) C: loss of coagulation leads to untreated water Supplied to consumers | ECM: Treatment process is halted to restore problem E: Yes | 1 | 2 | 2 | Lo | ||