Water Quality

Water Quality

1.        Bulk  Provision and Infrastructure Assets

The core bulk water and wastewater business is undertaken in a manner that most effectively serves customers and stakeholders. As part of the value chain function, raw water is carefully abstracted from dams, rivers and groundwater sources and conveyed using both gravity and the most effective pumping options to bulk water treatment works, where it is treated to meet SANS 241 quality standards and distributed to customers.

Equally, with regards to wastewater treatment, influent is received from municipal sewer systems, treated at bulk wastewater treatment works and effluent is discharged back into receiving systems mindful of the quality and potentially impacts on receiving systems and potential for reuse.

Umgeni Water’s infrastructure assets in support of its bulk water services business comprise:

  • Approximately 1260 kilometres of pipelines and sixty-seven (67) kilometres of tunnels,
  • Fifteen (15) impoundments,
  • Twenty (20) water treatment works, and
  • Eleven (11) wastewater treatment works. 

A total of 472 million cubic metres of potable water per annum (1294 Ml/d) are currently supplied to customers (Figure 1.1) who serve a population of 6.7 million or 1.9 million households through reticulation networks.

The entity treated bulk wastewater totalling 29 million cubic metres per annum (80 Ml/d) (32 million cubic metres or 87 Ml/d in 2018). The capacities of the different wastewater treatment works are shown in below (Figure 1.2). 

2.        Water Quality Management Approach

The quality of potable water is paramount to Umgeni Water thus the organisation endeavours to ensure that the quality of potable water produced within its operational area is safe to consumer health over a lifetime of consumption.  In order to achieve this, a comprehensive water quality management programme is implemented throughout the supply area. The programme adopts a risk-based approach including:  monitoring programmes, water quality assessments, system audits, compliance reporting and water safety plans embracing the catchment to consumer concept.

The risks associated with abstraction, conveyance, treatment and bulk distribution are constantly reviewed to ensure control effectiveness and quality assurance. Potable water quality incidents are managed in accordance with an Incident Management Protocol aligned to the requirements of the South African National Drinking Water specification (SANS 241).

In addition to providing safe drinking water and protecting public health, Umgeni Water is also committed to ensuring that wastewater discharges are not harmful to the environment and downstream users. This is achieved through the development and implementation of wastewater risk abatement plans which include comprehensive and site specific risk assessments, the implementation of corresponding mitigation plans and site specific incident management protocols to manage wastewater incidents and non-compliances.

All potable and wastewater sampling and analysis are undertaken in accordance with an ISO 9001 certified monitoring programme and SANAS 17025 accredited laboratory methods. Information on water quality performance is regularly conveyed to customers, stakeholders and regulators in accordance with the organisational stakeholder communication plan.

2.1 Potable Water Quality Performance

The South African National Drinking Water Specification (SANS 241:2015) dictates the compliance requirements for potable water supply systems. The performance of each system is reported against the following five risk categories specified in SANS 241:2015 (as per the classification tabulated further below):

(1) Acute Microbiological Health,

(2) Acute Chemical Health,

(3) Chronic Chemical Health,

(4) Aesthetic, and

(5) Operational categories. 

Key to classification of the performance of drinking water supply systems according to SANS 241: 2015

Population up to 100 000

Proportion of samples compliant

Population > 100 000

Proportion of samples compliant

Excellent Good Unacceptable Excellent Good Unacceptable
Acute Microbiological Health ≥97% ≥95% <95% ≥99% ≥97% <97%
Acute Chemical Health ≥97% ≥95% <95% ≥99% ≥97% <97%
Chronic Chemical Health ≥95% ≥93% <93% ≥97% ≥95% <95%
Operational ≥93% ≥90% <90% ≥95% ≥93% <93%
Aesthetic ≥93% ≥90% <90% ≥95% ≥93% <93%

 

For the assessment period 2018/19, thirteen (13) Umgeni Water bulk water supply systems and four (4) uMgungundlovu District Municipality (UMDM) schemes were monitored and reported against the five risk categories as specified in SANS 241:2015.

In March 2019, Umgeni Water acquired three (3) small water treatment works schemes from Uthukela District Municipality (uTDM) including: Ezakheni WTW, Oliphantskop WTW and Thukela Estate WTW.  These schemes were also monitored and reported against the five risk categories as specified in SANS 241:2015. Umgeni Water intends on assessing, maintaining and refurbishing or consolidating these schemes to provide a more sustainable bulk water solution to the areas supplied by the schemes in a similar manner that has been accomplished with the UMDM schemes.

Overall, compliance of the Umgeni Water bulk potable water supply systems was excellent for the reporting period. Compliance per SANS 241:2015 risk category is shown in Figure 2.1. Detailed potable water quality compliance per water supply system is shown in Table 2.1.

Table 2.1: 2018/2019 Potable Water Quality Compliance (%) with SANS 241:2015 per Water Supply System

 

Water Supply System Average daily volume treated (Ml/d) % Volume Percent Compliance with SANS 241:2015
Acute Microbiological Health Acute Chemical Health Chronic Chemical Health Operational Aesthetic
1 Durban Heights 503.0 35.65% 100 100 100 99.98 100
2 Wiggins 274.0 19.42% 100 100 100 99.84 100
3 Midmar 275.0 19.49% 100 100 100 99.65 100
4 DV Harris 95.0 6.73% 99.79 100 100 99.82 100
5 Amanzimtoti 80.0 5.67% 100 100 99.92 99.49 99.95
6 Hazelmere 59.0 4.18% 100 100 99.86 99.84 100
7 Lower Thukela 29.0 2.06% 100 100 99.87 99.7 100
8 Maphumulo 7.0 0.50% 100 100 99.78 96.35 98.61
9 Umzinto 14.0 0.99% 100 100 99.67 100 100
10 Mtwalume 12.0 0.85% 98.82 100 100 100 100
11 Mhlabatshane 6.0 0.43% 100 100 100 99.69 100
12 Maphephetheni 4.0 0.28% 100 100 100 99.64 100
13 Ixopo 2.3 0.16% 98.36 100 99.65 95.04 98.36
14 Mpofana 5.9 0.42% 98.81 100 100 96.53 100
15 Appelsbosch 0.4 0.03% 100 100 100 99.62 100
16 Rosetta 0.2 0.01% 100 100 100 99.26 100
17 Lidgetton 0.5 0.04% 100 100 100 95.58 100
18 Ezakheni* 37 2.62% 96.43 100 100 79.66 97.2
19 Thukela Estate* 0.8 0.06% 88 100 97.89 62 77.17
20 Oliphantskop* 6.0 0.43% 92.86 100 100 72.03 86.41

* System operated and monitored by Umgeni Water since March 2019

  The UMDM drinking water supply systems recorded a combined excellent performance against all the risk categories specified in SANS 241:2015. Since UW acquired these sites in 2016, an increasing trend in compliance is noted.  This is largely due to a number of interventions that have been implemented by UW including: the installation of 2Ml/day package plants at Mpofana WTW and Lidgetton WTW, the drilling of boreholes at Applesbosch WTW & Lidgetton WTW and the refurbishment of the slow sand filters at Applesbosch WTW.

The uTDM drinking water supply systems viz. Ezakheni, Oliphantskop and Thukela Estate recorded excellent performance against the Acute Health Chemical and Chronic Health Chemical risk categories whilst unacceptable performance was recorded in the Acute Health Microbiological and Operational risk categories. The Ezakheni system recorded excellent performance against the Aesthetic risk category whilst the Oliphantskop and Thukela Estate systems reported unacceptable performance. This was due to a number of issues including: varying raw water quality, the lack of optimisation or malfunction of treatment chemical dosing systems, challenges with the gravity sand filters, insufficient disinfection and aging plant infrastructure. Various mitigation measures have been implemented to improve compliance including process optimisation and the training of process controllers. Refurbishment of the treatment units at some works has also been instituted.

2.2 Wastewater Quality Performance

Figure 2.2 and Table 2.2 show wastewater quality compliance per system, assessed against the relevant licence or General Authorisation General Limits prescribed by the Department of Water and Sanitation (DWS). 

Table 2.2: Wastewater compliance per treatment works

Wastewater Treatment Works Average daily volume treated 2015 2016 2017 2018 2019
(Ml/d) (%)
1 Darvill 67.2 83.7% 85% 82% 72% 73.8% 73.7%
2 Howick 5.5 6.9% 87% 89% 86% 91.1% 90.3%
3 Ixopo 0.5 0.6% 96% 93% 94% 96.0% 94.0%
4 Lynnfield Park 0.2 0.3% 87% 86% 96% 95.9% 93.6%
5 Mpofana 5.6 7.0% 65% 72% 78.0% 77.7%
6 Richmond 0.6 0.7% 89% 87% 93.9% 96.7%
7 Cool Air 0.4 0.5% 90% 98% 98.2% 99.6%
8 Camperdown 0.2 0.2% 91% 97% 91.7% 91.7%
9 Applesbosch 0.1 0.1% 94% 91% 81.9% 88.9%

 

Effluent compliance for the Umgeni Water Bulk Wastewater Systems decreased marginally from 81.7% to 81.29% for the reporting period.  Once again, an increasing trend in effluent compliance is noted for the UMDM sites following a number of interventions that have been implemented by UW including: process optimisation, installation of electrical panels and aerators and the refurbishment of a number of process units. A notable increase in effluent compliance was observed at Mpofana WWTW where a number of mitigation measures were implemented such as the refurbishment of the clarifiers, upgrade of pumps, optimisation of the sludge dewatering machine and the dredging, refurbishment & reconstruction of the reed beds.

The non-compliance recorded for Darvill WWTW was mainly due to construction related activities as well as process overloading, trade effluent inputs, power outages and intermittent spillages from the storm dam. The upgrade work currently remains on hold, with some process components being incomplete thus compromising the efficiency of the treatment process. The completion of the works upgrade project remains critical to increase capacity and improve effluent compliance.  The proposed constructed wetland, for detention of some storm dam spills, will also have a significant benefit once completed.

 

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