Problems with Bore Water. With the amount of effluent, heavy metals and carcenogens such as DDT, SELENIUM, ARSENIC and CADNIUM etc etc that have flowed down the river and settled in the lakes and found their way into the Aquifers over the years you would think that the Government would understant why we refuse to drink bore water. Critters and Crap – A Tale of Contaminated Water Peter Boland Team Leader Environmental Health Darling Downs Public Health Unit In February this year the Darling Downs Public Health Unit was contacted by a resident of a small rural community. She advised that over the past five years her family, and herself, had been suffering gastro intestinal symptoms allegedly due to the consumption of contaminated water. The family’s primary source of water was from a private bore which draws from a sub-artesian aquifer. This water was reticulated throughout her house. The Council and another government department had recently tested the water which was found to contain E. coli. She expressed concerned that other people in town were also experiencing gastro intestinal symptoms and suggested that the aquifer was contaminated by the 2010 floods. In Queensland water related issues are managed by several different agencies and pieces of legislation. The Public Health Act 2005 defines what is classed a public health risk and allocates responsibility for managing these risks to either State or Local Government. In this instance the water that was alleged to be causing the problem was not supplied by the Council, or another water service provider, nor was it recycled water produced or supplied under a recycled water scheme. As such section 11(1)(b)(iv) of the Act defines this situation as a Local Government public health risk. The complainant was advised to boil or otherwise treat all water for human consumption. She was also encouraged to seek medical advice and have faecal specimens obtained from those family members experiencing diarrhoea. The matter was discussed with the Council, who subsequently obtained a range of water samples from throughout the town. All of these samples were from premises using bores pumping from the sub-artesian aquifer. Seven (7) samples were taken in total, all of which were subsequently found to contain E. coli. Three (3) of the samples were reported as having >200 MPN per 100ml. Upon discussing the results with the Public Health Unit, Council immediately issued a “boil water alert” to the community. They also took measures to ensure that water was not consumed from publicly accessible taps available throughout town. Council was also requested to continue to take water samples throughout town at least weekly. Council primarily reticulates artesian water, which comes from an aquifer more than one (1) kilometre underground, throughout town. This water comes out of the bore head at around 99ºC. Most residents use this water as their hot water supply and use private bores, drawing from the shallow sub-artesian aquifer, and rainwater tanks for human consumption and other domestic purposes. Members of the community expressed several further opinions about the possible cause for the contamination of the aquifer including: The town’s common effluent disposal (CED) scheme overflowing from the pump station into the nearby creek; Damaged septic tanks; and Page 2 of 5 Illegal building and plumbing work, including the construction of cesspits. At this time the Unit was in the midst of responding to the flooding across South West Queensland. We had also received a notification concerning a viraemic dengue case in an area known to have Aedes agypti. A Queensland Health incident management protocol was subsequently implemented. This enabled addition resource from across the organisation to be redirected to assist in managing the response to this matter. A search of the notifiable diseases database (NOCS) showed that only one resident of the town, a 12 month old child, had recently been notified as having salmonellosis. The child’s mother was subsequently contacted to obtain an exposure history. No consumption of subartesian water was reported. The Unit’s Communicable Diseases Team contacted the town’s residents to gauge the extent of the gastro intestinal illness in the community. A total of 13 people were contacted out of 24 properties. An additional, nine (9) people reported to have suffered gastro intestinal illness in the last six months. Of these nine (9) people, only two were identified as having consumed water from a sub-artesian bore. Council does not have the services of a full time Environmental Health Officer. An Environmental Health Consultant is engaged as required. Council arranged for their consultant to conduct an assessment of the town to determine the possible source of contamination. During the investigation four (4) septic tanks that had not been replaced when the CED scheme was constructed, approximately 10 years ago, were identified. In his report he noted that no geotec testing was carried out on the CED scheme. It was also noted that the scheme had not been approved by the Department of Environment and Resource Management (DERM). Among other things, he recommended to Council that they carry out “a geotec investigation of the CED scheme to determine the integrity of the scheme and its relationship to the creek and underground aquifer”. Council subsequently engaged a geotechnical engineering consultant to provide technical assistance on the matter. This consultant concluded that it was unlikely that the creek or CED lagoons were the source of contamination of the sub-artesian aquifer. The report also discounted septic tanks as the source of contamination due to subsurface clay slowing the travel of any escaping effluent. It was suggested that any E. coli would not survive outside a host for more than several days. Due to the elimination of other potential sources of contamination, the report concluded that rodents or their dropping were tainting the water. It was recommended that open bores be chlorinated and capped. The report was subsequently reviewed by the Acting Chief Hydrogeologist from DERM. He advised that while the conclusions that were drawn in the report may be correct, the methodology used by the consultant was questionable. He indicated that further testing was required and suggested Microbial Source Tracking (MST) analysis to determine whether the contamination was of animal or human origin. Advice was also received from the Supervising Scientist from Queensland Health Forensic and Scientific Services concerning the survival rate of E. coli in the environment. He indicated that E. coli would survive for weeks not days as suggested in the Consultant’s Report. Page 3 of 5 The Incident Management Team determined that critical assumptions within the report relied on incorrect information therefore its conclusions were seriously flawed and were unlikely to resolve the issue. It was felt that the consistent wide spread high levels of E. coli in the water was suggestive of a problem greater than rodent contamination of the bores. A sampling plan was developed to test the various hypotheses on the source of contamination. Pre and post flush samples would be taken to compare the water standing in the bore casing with that from the sub-artesian aquifer. A range of bacteriological and chemical tests were proposed to determine whether the contamination was from human or animal origin. While many of the bacteriological tests were indicative of faecal contamination they would not be specific to human faeces. However, it was thought that a sustained level of faecal indicators across a number of bores and over time is unlikely to result from rodent infestation of individual bores. Microbial Source Tracking (MST) and Bacteroides analysis by CSIRO would confirm that the contamination source is human rather than rodent. The detection of pharmaceuticals in the water would also indicate the presence of human sewage. Samples were also proposed to be taken from the artesian bore to determine if this was a suitable alternative water supply. The following samples were proposed: • E. coli (pre and post flush) • Enterococci (pre and post flush) • Clostridium • Coliphages • Microbial source tracking (MST)/bacteroides • Pharmaceutical screen • Endocrine disrupting chemicals (EDC) screen • Hydrocarbons/Volatile organic compounds (VOC)/benzene, toluene, ethylbenzene and xylene (BTEX) • Total petroleum hydrocarbons (TPH) • Standard water analysis (SWA). A team of two (2) Environmental Health Officers, a Public Health Medical Officer and a Hydrogeologist travelled to the town to conduct water sampling, collect information about bores and attend a public meeting about the water. Samples were obtained from six (6) sub-artesian bores spread throughout the town, the town’s artesian bore, the creek and one of the CED effluent ponds. The construction of the bores varied. Some bores were fully sealed while others were uncapped and open to the environment. The sample results showed that the microbial contamination (Table 1) was less widespread than in previous sampling. Three (3) sites were all positive for both E. coli and enterococci and two (2) of these three (3) had elevated readings for Clostridium perfringens. A fourth site was positive for enterococci only. There was no significant difference in results before and after flushing. Somatic coliphages were detected at one (1) site, the creek and the CED lagoon. Three (3) sites were positive for human-specific HF183 Bacteroides, which is a definitive test for human faecal contamination. One (1) of these sites was also positive for the enterococcal surface protein gene (esp). HF183 and the esp gene were not detected in the CED lagoon, as sampling was only possible at the edge of the lagoon, where sunlit, aerobic conditions make survival of these anaerobic bacteria unlikely. Had sampling in the centre of the lagoon been possible, positive results would have been more likely. It is clear from these results that the most faecal contamination was centred around site 4. Page 4 of 5 Table 1 - Microbial results from sampling (ND indicates not detected, NA indicates the test was not applicable and therefore not carried out). Description Before flush After flush Somatic coliphages (pfu/100mL) FRNA coliphages (pfu/100mL) HF183 bacteroides esp gene Clostridium perfringens (cfu/100 mL) E. coli (mpn/100 mL) Enterococci (cfu/100 mL) E. coli (mpn/100 mL) Enterococci (cfu/100 mL) Site 1 2 ND 5 5 ND ND + ND ND Site 2 8 22 2 51 ND ND ND ND 21 Site 3 ND ND ND 44 ND ND ND ND ND Site 4 >200 >100 >200 >100 56 ND + + 460 Site 5 ND 3 ND ND ND ND + ND ND Site 6 ND ND ND ND ND ND ND ND ND Creek 160 1200 0 NA NA 530 ND ND ND 87 CED lagoon 8400 3700 NA NA 3500 11 ND ND 3000 Over 30 chemicals were identified in the CED lagoon, including a range of pharmaceuticals and other chemicals commonly used as indicators for sewage contamination of environmental waters. A small number of pesticides were also detected at trace concentrations. Of these chemicals, only a minority were also detected in the bores, including acesulfame K (at two {2} sites), DEET (at two {2} sites) and the pesticides dicamba and diuron (at one {1} site). Cholesterol was detected in four (4) of the sub-artesian bores. The artesian bore was found to be very high in TPH (1735 μg/L). The odour threshold for petroleum hydrocarbons in drinking water is 10 μg/L. There is no guideline for TPH in the Australian Drinking Water Guidelines, but Queensland Health has determined that a standard of 200 μg/L is appropriate for Coal Seam Gas produced water that is released into a drinking water source. The only exceedance of a health based drinking water standard was reported from the artesian bore with 3.2 mg/L of fluoride. It was also found to exceed the aesthetic guidelines for sodium and total dissolved solids. The results clearly show that the sub-artesian aquifer is contaminated by human sewage. The extent of contamination appears to have diminished since earlier in the year. This may be as a result of the decreased usage of this water by the community following the institution of the “boil water alert”. The very high microbial detections in samples from one bore, the presence of the esp gene and HF183 Bacteroides, and detection of acesulfame K and DEET strongly suggest that the source of the contamination is likely to be close to this bore. The artesian bore is unlikely to be a suitable drinking water source, due to elevated concentrations of fluoride, sodium and TPH. Page 5 of 5 While the source of the contamination has been shown to be of human origin, further work needs to be undertaken to indentify the source. The following recommendations were provided to Council: 1. That the suspect septic tanks be emptied, examined and replaced if necessary; 2. That the integrity of the CED gravity mains be checked; 3. That the adequacy of the CED pumping station be reviewed to ensure that effluent does not overflow into the creek; and 4. That a hydrogeological survey of the sub-artesian aquifer be undertaken. They were also reminded that residents should assess their bore’s casing and ensure that the bore head is capped and sealed. To address the immediate health concerns of residents, Council resolved to fund the installation of UV treatment systems to residential properties in town. They canvassed residents to determine the uptake of this offer. UV treatments systems have now been fitted for all residents who opted into the offer. Council has undertaken pressure testing of the rising main at the pumping station and are checking the gravity mains. No problems have been reported to date. Consulting Engineers have been engaged by Council to investigate options to provide a more stable power supply to the pumping station. The consultants will also provide advice to Council on longer term water supply options such as deepening the existing artesian bore and drilling a new bore, to source water from a different aquifer. Council has applied for government funding to progress a new water source for the town. This case study highlights the importance of testing any hypothesis developed during an investigation with a targeted sampling program. Incorrect assumptions can lead to delays in resolving the issue and, in the long run, cause unnecessary work and costs. A wide variety of tests are now available to assist those tasked with the investigation of contaminated water. The sensitivity and specificity of these tests are continuing to improve. New tests are also emerging, such as microbial source tracking. We need to embrace these new and improving technologies to assist in our investigations. Acknowledgements Numerous people from the following organisations were involved in the investigation and management of this matter: • Queensland Health - Darling Downs Public Health Unit - Gold Coast Public Health Unit - Water Quality Unit - Queensland Health Forensic and Scientific Services • CSIRO • Former Department of Environment and Resource Management • Council I would like to thank all of those involved for their contribution.
Posted on: Sun, 11 Jan 2015 05:58:47 +0000
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