CHAPTER 4 RESULTS AND DISCUSSION
4.2 Water quality re-evaluation (Research Objective 1)
4.2.4 Evaluation of microbiological characteristics
Faecal coliform is generally used to evaluate the presence of bacterial pathogens transmitted in faecal matter. Faecal Coliform range (counts per 100 ml) should ideally be 0 but 1 is generally accepted as tolerable. Counts up to 10 present risks of microbial infections with continued exposure with counts up to 20 posing a risk of transmission of infectious diseases (DWAF, 2003).
The TWQR for microbiological (Faecal Coliforms) measured in counts per 100 ml for irrigation purposes is <1 c/100 ml, livestock watering is less stringent at 200 c/100 ml whereas for domestic
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drinking purposes it is set at 0 c/100 ml (DWAF, 1996a-f). The BGWMA RQO use E. coli as measure of pathogens and is set at 165 c/100 ml (SA, 2018).
Both DWAF and BGCMA monitored the microbiological water quality in the BGWMA; however, the DWAF monitoring dataset was particularly incomplete and could therefore not be used. Data from the BGCMA monitoring stations for the Upper and part of Middle Breede River sections are more complete for the period 2008 to 2020 and were therefore utilised in the evaluation of the microbiological water quality in the study area (Table 4-4 and Figure 4-17). The biological monitoring data for each monitoring station is presented in Annexure I and time series data plots in Annexure J.
Table 4-4: BGCMA microbiological water quality monitoring sites (CWDM, 2010; BGCMA, 2021).
Sample
station ID Brief locality description of sample station
LAT.
DECIMAL DEGR (S)
LON.
DECIMAL DEGR (E)
CER 1 Ceres (Oewersig) 33,3604 19,3008
CER 2 Ceres- Dwarsrivier (Eilandplaas) 33.3745 19.3182
CER 3 Ceres (sewerage farm bridge) 33.3826 19.3121
CER 4 Ceres-Wolesley (Witbrug) 33.4217 19.2671
CER 5 Ceres (La Plasante bridge) 33.4480 19.2061
CER 6 Ceres (Bainskloof bridge) 33.5198 19.1858
WOR1 Worcester-Rawsonville Edelweis bridge 33.6517 19.3344
WOR2 Worcester-Rawsonville Nekkies bridge 33.6849 19.4209
WOR3 Worcester east pumping station 33.6979 19.4578
WOR4 Worcester Climor bridge 33.7368 19.4871
WOR5 Worcester Eilandia River camp 33.7695 19.6131
Variations between the stations as well as over time was evaluated and where possible correlations between parameters were identified. Based on the Coliform and E. coli TWQR for irrigation and BGWMA RQO limits the majority of the stations exceeded these limits at regular intervals with Faecal Coliform counts as high has 240 000 c/100 ml and E. coli counts of up to 110 000 c/ 100 ml recorded at stations higher-up in the Upper Breede River section (Figure 4-18 and graphs in Annexure J). The stations between Ceres and Worcester recorded the highest Faecal Coliform and E. coli counts mainly in 2011, 2014 and again in 2019.
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Figure 4-17: Location of BGCMA monitoring stations for microbiological parameters (modified from BGCMA, 2021).
The monitoring stations between Worcester and Robertson (Middle Breede River section) showed a similar trend although the levels rarely exceeded 1 000 counts/ 100 ml with the monitoring station downstream of Rawsonville (Wor1) more regularly exceeding the limits prior to 2015. An alarming trend is the elevated levels for E coli (up to 6 000 c/100 ml) recorded more recently (2019-2020) at stations (Wor 2 and Wor 3) downstream from Worcester (Figure 4-18 and Annexure J). The elevated E coli levels observed at these stations downstream of Worcester either suggest that the WWTW is not operating optimally which is contrary to the compliance findings by WCG (2017) and Cullis et al. (2018), or indicates the contribution from the un-serviced informal settlement have increased.
The highest levels were generally recorded in late summer/ early autumn when the flow in the streams were low with lower values generally coinciding with winter rainfall periods (and Annexure J). The E. coli lower levels during winter months suggests that the majority of the E. coli is removed from the system when the system is flushed during floods.
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Figure 4-18: Spatial variation in the microbiological (E. coli) water quality for selected BGCMA monitoring stations for the Breede River.
There are 82 WWTWs within the BGWMA, of which 21 are municipal WWTW ranging in size from 30 Ml/d for Worcester to less than 1 Ml/d in the smaller towns (BGCMA, 2017b WCG, 2017). The majority of the WWTW (70%) are small, treating less than two (2) Ml/d (BGCMA, 2017b). Of these WWTW 41% are oxidation ponds, 6 % are biofilters and the remaining 53% are activated sludge plants. Not all WWTW are fully compliant with legal requirements including authorisation (BGCMA, 2017b). The BGCMA (2017b) study showed that 28% of the 82 WWTW did not have any authorisation, 27% are authorised under General Authorisation, and the remainder either have existing permits or a Water Use Licence.
The level of compliance of the municipal WWTW was evaluated by several studies based on compliance with microbiological and chemical requirements (CWDM, 2010; WCG, 2017; Cullis et al., 2018). A summary of the findings from these studies for relevant municipal WWTW are presented in Annexure J. Based on the Green Drop System, the CRR risk rating indicates that the majority of the plants in the study area are rated as either high or medium risk plants.
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The incentive-based regulation Green Drop certification programme was developed in 2008 to highlight risks and priority areas. Compliance in terms of effluent quality discharged to the receiving water resource as well as plant design capacity and technical skills were used to identify risks. Compliance is reported as Cumulative Risk Rating (CRR), which is a risk calculated against the Design Capacity of plant where WWTW with a high CRR value indicating that the plant has reached or is approaching its critical state of operation and therefore requires intervention such as upgrading/ capacity expansion (DWS, 2014).
By comparing the results from previous studies the impression is that the level of microbiological compliance of most WWTW improved between 2010 and 2018, the only exception being Montague (Annexure J) (CWDM, 2010; WCG, 2017; Cullis et al., 2018). Worcester, Ceres and Wolseley generally have the best compliance levels with Ceres showing the best improvement since 2010. However, the E coli levels since 2018 do not reflect this improvement with microbiological water quality at most stations downstream of Ceres, showing elevated levels, with up to 45 000 c/ 100 ml recorded (Cer 3 downstream of outflow of Ceres WWTW) (Annexure J).
Compliance improvements were reported for Worcester and Rawsonville which reflects the upgrading of the WWTW, although some incidents where the E coli standards were exceeded at stations downstream of Worcester were recorded since 2019 (Figure 4-18 and Annexure J).
Discharges of treated waste water from the WWTW at Rawsonville and Worcester have a negative impact on water quality in this segment (and downstream areas). Of concern are the low levels of compliance to the microbiological standards reported for Robertson (CWDM, 2010; Cullis et al., 2018).