DATE:
TITLE: Microbiological examination of the Garavogue River and Sligo Estuary.
AIMS:To carry out a microbiological examination of the Garavogue River and Sligo Estuary.
INTRODUCTION:In this practical a microbiological examination of the Garavogue River was to be carried out from its source to the Estuary.In this analysis of this area the following was tested for;Coliforms, Faecal Streptococci, Clostridia, Psychrophiles and Measophiles.Samples for analysis were taken from nine different locations from the Blue lagoon to Cregg Estuary.
The Garavogue is a small river approximately 4km long flowing out of Lough Gill into the Atlantic Ocean at Rosses Point and as such is the main route for transport of water pollutants out of Sligo town along with the tidal cycles flushing the estuary.Lough Gill is known to be a fairly eutrophic lake and the Garavogue river has a history of being of good quality.The land surrounding both the lake and river is mainly woodland with some grazing land for cattle and sheep, no other intensive agricultural practices are carried out in the area and there should therefore be no sources of artifical fertilizers, pesticides, slurries or silage effluents entering the Garavogue or Lough Gill, which would cause pollution of the river and estuary by organic enrichment.
A sample was taken from a point opposite the Blue Lagoon and this was known as sampling site no.1. This site was expected to be fairly clean as it is only 300-400m from Lough Gill.
The second site chosen was just behind the Bank of Ireland.Like the previous site this site was also expected to be fairly clean in comparison to some of the following sites. Also this site is not affected by the tide, so none of the discharge from the town sewer will reach this point.
Quay Street sampling site is at the start of the areas influenced by the tide.This was the third site chosen. Several discharges of effluent of mainly domestic origin, include effluent from the Silver Swan and several small upstream discharges all contribute to the pollution load on the river and estuary.
A sample was also taken from Deep water quay (sample site 4) where the holding tank for the town’s sewage is and up to 2 million gallons can be discharged per day. Another discharge at this point which would consist of animal wastes and blood come from the Avonmore meat prossessing plant. This sample was taken on an incoming tide, so some of the discharge would be washed back up the estuary and river.
Gibralter is situated on the southern shore of Sligo estuary, about 2km from Sligo town centre.This site was site 5 and at this point Sligo Daries discharge effluent which mainly consists of washings from holding tanks.When the tide is low a milky white colour can be seen, the reason for this is that the dilution is not great enough to disperse the effluent. This point would also be affected by the main domestic sewage discharge and leechate from the now closed landfill.The sample here was also taken as the tide was coming in.
Another sampling point was at Cartron sea (sample site 6) Cartron is a shallow inlet and is completly uncovered at low tide except by a stream and flows at low tide into the main channel opposite the Deep water quay. The salinity of the water in Cartron is variable due to the imput from the Garavogue river. The Sligo sewerage scheme currently discharges to the estuary some 300m upstream from Cartron Point. There are several other point discharges of effluent from Cartrom housing estate, gross faecal and other sanitary materials are constantly to be seen floating away down stream of both these outfalls,these all contribute to pollution in the inlet. This sample was taken on a falling tide.
A seventh sample was obtained from a site on Donally River, so as the effects of this river on the estuary could be assessed.This site was sampled on an out going tide.
Cregg stream was also sampled,this was the eigth sampling site.Cregg stream was sampled so as to determine its quality and its impact if any on the estuary.
The final sampling location was out at Cregg estuary, once again it was sampled to see what effect if there is any on this estuary due to the discharge of the town’s sewerage.
One of the many unfavourable effects of municipal wastes is the contamination of the recieving enviroments with bacteria, viruses and other orgasinmsof public health significance. Pathogenic organisms, especially those from the intestines of warm blooded animals, frequently persist in waters for sufficent periods of time and distance to pose a threat to the health and well being of unsuspecting water users.Secondary chances to exposure to these orgasims exist through the contamination of shellfish which are harvested for food.
In Sligo the sewerage scheme is a combined drainage system and at present discharges to the Sligo harbour estuary without any treatment. Construction of a sewerage treatment works for Sligo town is expected to commence in a year or so.
MATERIALS: As per Standard Methods.
METHODS: As per manual
RESULTS:
Total Coliforms 50 ml filtered
Result: =>TNTC
Faecal coliforms 50ml filtered
Result: => 2.2 x 103 cfu/100ml
Faecal Streptococci 100ml filtered
Result =>1.7 x 103
Clostridium perfringins 1 x 50ml +ve
5 x 10 ml +ve
Result =>18 psrc
Gram stain from +ve tube
Result => Gram +ve rods typical of sulphite reducing clostridia.
DISCUSSION:In this practical a microbiological examination was to be carried out on the Garavogue River and Sligo Estuary. Nine different sampling locations were chosen from the Blue Lagoon to Cregg estuary in an attemp to assess the quality of the whole area.
Group 6 carried out an analysis at Cartron Sea and the sample here was taken on an out going tide.The total number of psychrophiles found was 3.2 x105 cfu/100mls.This result represents the naturally occuring population of microorganisms (m/os)at this site.A naturally unpolluted water body has higher numbers of psycrophiles than measophiles.The m/os present here were also halophilic (salt liking).The total aerobic measophilic bacteria at this point was found to be 1.85 x 106 cfu/100mls which is a higher figure than obtained for the psychrophiles.Also this result would indicate the introduction of pollution,A total coliform analysis was carried out and the numbers found were too numerous to count (TNTC).Also a faecal coliform analysis was carried out and the numbers found were 2.2 x 103 cfu/100mls by using the membrane filter method.Another faecal coliform analysis was preformed using the pour plate method and the result found was 6.0 x 104 cfu/100mls. A faecal streptococcal analysis was also carried out and the result obtained was 1.7 x 103.From these results it can be said that the water here is heavily contaminated with coliforms which indicates pollution.Higher nos of faecal coliforms than faecal streptococci were observed at this site which indicates pollution from either human or animal origins. This pollution may have come from the main sewer which is about 300m upstream of the site sampled, some of which gets washed back up the the lower estuary when the tide comes in . Also some of this pollution may have originated out of Cartron itself which is a large housing estate or maybe some of it could have come from agricultural practices in the area.This site was also seen to contain sulphite reducing clostridia and a result of 18+ presumptive sulphite reducing clostridia (psrc), then a gram stain was carried out and gram positive long rods were observed, which are typical of sulphite reducing clostridia.The presence of sulphite reducing clostridia in the sample indicate pollution a long time ago as these organisms are present in water as spores and can with stand extremes in enviromental conditions.From the analysis carries out it can be said that the water here does not meet the E.C. Regulations for Human Consumpion or Bathing waters.
The first site sampled was up at the Blue Lagoon which is about 400-500m from Lough Gill.This site was expected to be of good quality as it is so close to the lake from which 2/3 of Sligo water supply is obtained.However from the results reported there are higher nos of measophiles at this site than at the two following ones.Also a high no. of total coliforms were observed (2.8x 103 cfu/100mls) and as well a result of 1.5 x 102 cfu/100mls was found for faecal coliforms by the membrane filter method, which indicates pollution occured.The no. of faecal streptococci found was 75 cfu/100mls, which also indicates pollution. The nos of sulphite reducing clostridia found was 18+ psrc. This site does not meet the requirements of the E.C. Directive 80/778/EEC for Water for Human Consumption, as no total or faecal coliforms, and faecal streptococci should be present per 100mls of sample tested using the membrene filter technique.Further more there should be no sulphite reducing clostridia present per 20 mls of sample analysed using the above method. So from these results it can be said that the water here at this site would need some treatment prior to abstraction for human consumption.
The second sampling site was behind the Bank of Ireland (BOI) and a full assessment of the water quality here could not be made as some of the results went missing.However the no of measophiles was seen to be lower than those seen at the site at the Blue Lagoon.The no of psychrophiles found at this site were 5.0x 103fu/100mls.So at this site the nos of measophiles exceed the nos of psychrophiles which indicates pollution. A result of 9 psrc was obtained for the sulphite reducing clostridia,which indicates pollution a long time ago.This pollution may have have come from a holging tank which is beside where the mill house is and when it rains heavily this tank over flows into the river.
The third site sampled was at Quay street and this site is where the tide reaches when it is fully in.at this site the nos of psychrophiles here is 5.36 x 104 cfu/100mls ents the naturally occuring at this point.The measophiles reported are lower at this point are lower than that seen at the previous sitesHigh nos of total and faecal coliforms were obtained, along with high nos of faecal streptococci, which indicates pollution which may be coming from the Silver Swan hotel which is close to this site.A result of 9 psrc was obtained for the analysis for sulphite reducing clostridia,which indicates pollution some time ago.
The fourth site tested was out at Deep water quay and this the point where the main sewer from Sligo discharges the town sewage.At this site high nos of psychrophiles and measophiles were obtained.the nos of total coliforms, faecal coliforms and faecal streptococci were uncountable at this site using the membrane filter method. A count for faecal coliforms using VRBA agar was found to be 6.26 x 105 cfu/100mls. The results at this site was as expected,as this site suffers from gross pollution which originates in Sligo town.
The fifth site was out at Gibralter and this site is where alot of effluent is been dischargedby NCF Dairies.The no of psychrophiles recorded at this sise was lower than that found at the previos site this is probably due to dilution.No count could be obtainted for toal coliforms, faecal coliforms and faecal streptococci at this site as they were to numerous too count.a result of 18+ prsc was obtained for the sulphite reducing clostridia.
An analysis was carried on the Donally River which flows into Sligo Estuary.This river was seen to have high nos of both psycrophiles and measophiles present.The total coliforms and faecal coliforms were uncountable. A faecal streptococci count of 2.39 x 102 was found.The result obtained for the faecal coliforms by the pour plate method,yielded a result of 5.3 x 102.This rivers pollution would come from agricultural sources