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En v ir o n m e n t Ag e n c y Investigation into the Effect of Sewage Disinfection on the Bioaccumulation of Chloroform, Bromoform, Dibromochloromethane and Dichlorobromomethane by Fucoid Seaweeds. Mitch Perkins - June 1996 South West Environment Agency E n v i r o n m e n t A g e n c y Information Services Unit Please return or renew this item by the due date Due Date H-i- CONTENTS 1. ABSTRACT 1 2. INTRODUCTION 1 2.1 Background 1 2.2 Study Aims 1 2.3 Outfall Details 2 3. METHODS 2 3.1 Site Selection 2 3.2 Sampling Regime 2 3.3 Seaweed Analysis 3 4. RESULTS 3 4.1 West Huntspill 3 4.2 Minehead 3 4.3 Kingston Seymour 4 4.4 Black Rock 4 5. DISCUSSION 5 5.1 West Huntspill 5 5.2 Minehead 5 5.3 Kingston Seymour 6 5.4 Black Rock 6 5.5 April and November Levels of THMs 6 6. COMPARISON OF 1994 WESTON-SUPER-MARE DATA WITH PREVIOUS RESULTS (1991-1993) 7 7. CONCLUSIONS ' 8 8. REFERENCES 9 APPENDIX I Levels of Trihalomethanes in Fucoid Seaweeds along the North Wessex Coast 1994 APPENDIX H Levels of Chloroform, Bromoform and Dibromochloromethane in Fucoid Seaweeds. Black Rock 1991-1994 ENVIRONMENT AGENCY 1. ABSTRACT Spatial and temporal patterns in the bioaccumulation of trihalomethanes (THMs) were investigated in relation to the. disinfection of four sewage effluents along the North Wessex coast (Minehead, Bumham-on-Sea, Weston-Super-Mare and Kingston Seymour). Seaweeds (Fucus vesiculosus or Fucus serratus ) were collected four times during 1994 in April, June, September and November (before, during and after the disinfection period). Tissues were analysed for chloroform, bromoform, dibromochloromethane arid dichlorobromomethane. Increases in levels of chloroform and bromoform during June and September at Burnham Slip and sites adjacent to the West Huntspill outfall were believed to be related to the disinfection process. The highest levels of chloroform were recorded from Bumham Slip. The possible combined impact of disinfected effluent from West Huntspill and Chiltem Trinity S.T.W.s is discussed. The discharge from Minehead appeared to have only a limited impact on local beaches. High levels of bromofonn at Porlock are discussed in relation to the disinfection scheme. No clear relationship was seen at Weston-Super-Mare in 1994, but previous studies did suggest a connection between the disinfection at Black Rock and the distribution of THMs within seaweeds collected from Weston Bay. Past data is discussed. No relationship could be demonstrated between the levels of THMs accumulated in seaweeds and the disinfection process at Kingston Seymour. There appeared to be no clear relationship between the disinfection process and the levels of dibromochloromethane recorded from seaweed tissues during this study. Detectable levels of dichlorobromomethane were not observed. Seaweed from a number of sites were found to contain THMs outside the disinfection period. Possible reasons for this are discussed. 2. INTRODUCTION 2.1 Background / Sewage disinfection has been adopted at a number of outfalls on the North Wessex coast to reduce levels of faecal bacteria and comply with the E.C. Bathing Water Directive (Council Directive 76/160/EC). Disinfection is achieved by dosirig the effluent with chlorine based compounds (eg. sodium hypochlorite). However, the resulting discharge ■ can be deleterious to aquatic organisms. The toxicity of chlorinated wastes and waters has been demonstrated on a number of marine fish and invertebrates (Davis & Middaugh, 1977). Effects ranged from avoidance, inhibition of motility and fertilization to 100% mortality. List I of the Dangerous Substances Directive (76/464/EEC) contains substances selected on the basis of their toxicity, persistence and bioaccumulation. This includes substances belonging to the organohalogen group. Chloroform is already controlled by a daughter directive (88/347/EEC) and has an Environmental Quality Standard of 12jig/l. Halogenated organic compounds (including trihalomethanes such as chloroform) are known by-products of the disinfection process. The discharge of disinfected sewage from several outfalls along a relatively short stretch of coast could be potentially harmful to the local aquatic environment. 2.1 Study Aims * The aim of this study was to investigate spatial and temporal patterns in the bioaccumulation of trihalomethanes (THMs) in relation to the discharge of disinfected effluents along the North Wessex coast. High levels of THMs accumulated during the bathing season would suggest an impact from sewage disinfection. Similarly high levels recorded from sites closest to, or most likely to receive effluent from, the outfall.would suggest that the probable source of these compounds was the disinfected discharge. 1 A bioaccumulation programme was undertaken during 1994 using fucoid seaweeds (Fucus vesiculosus or F. serratus depending on availability), to investigate effluent disinfection at Minehead, Bumham-on-Sea, Weston-Super-Mare and Kingston Seymour. This was an extension of the bioaccumulation work undertaken at Weston-Super-Mare in 1991,1992 and 1993 (N.R.A. South Western Region, 1993). 2.2 Outfall Details Of the four outfalls studied only Minehead discharges directly into the Severn Estuary. The others all discharge into the estuary via rivers or creeks which have a reduced capacity for dilution at low tide (West Huntspill and Bridgwater via the River Parrett, Black Rock via the channel of the River Axe and Kingston Seymour via Kingston Pill). During the summer bathing season, the outfalls undergo disinfection to ensure that local beaches satisfy the requirements of the E.C. Bathing Water Directive (Council Directive 76/160/EC). The summer bathing season is defined as beginning on the first Monday in May, which falls a fortnight before the Spring Bank Holiday and ending on the Sunday which falls in the second full weekend of September (D.O.E. COPA/1288). In reality the discharge period is usually longer than this due to pre-season trials and post-season run down (Table 1). Table 1 Period of Disinfection Outfall Start End Black Rock - Weston-Super-Mare 23.04.94 . 01.10.94 Minehead 27.04.94 03.10.94 Kingston Seymour 23.04.94 05.10.94 West Huntspill - Bumham-on-Sea 27.04.94 02.10.94 Chilton Trinity - Bridgwater* 27.04.94 30.09.94 3. METHODS 3.1 Site Selection Samples of fucoid seaweeds (Fucus vesiculosus or F. serratus depending on availability) were collected from a total of 23 sites along the Severn Estuary between Clevedon (Avon) and Porlock (Somerset) on the North Wessex coast (Figure 1). Nine of the sites already existed as part of the Weston-Super-Mare bioaccumulation programme. Additional sites were selected on the following criteria; a) Distance frorin outfall . ' b) Presence of hard substrata and fucoid seaweeds c) Access to foreshore Due to the proximity of the Kingston Seymour, West-Huntspill and Black Rock outfalls some of the sites overlapped. 3.2 Sampling Regime Samples of fucoid seaweeds were collected before, during and after the disinfection period (Table 2). Fucus vesiculosus was collected from all sites with the exception of Ladye Bay (one of the reference stations), where only F. serratus was available. Approximately 15-20 plants were collected from each site and transported to the N.R.A's Blandford Laboratory under cool and dark conditions. * The effluent from Chilton Trinity could not be directly monitored due to the lack of fucoid seaweeds in the area. Details of the discharge have still been considered due to the potential combined effects of this effluent and the West Huntspill discharge. FIGURE 1 LOCATION OF SAMPLING SITES - Disinfection Bioaccumulation Study 1994 Table 2 Seaweed Collection Dates Outfall Pre Disinfection During Disinfection Period Post Disinfection Black Rock 7th April 6-7th June 19th, 21st Sept. 2nd Nov. Minehead 18th April 9th June 22nd Sept. 7th Nov. Kingston Seymour 21st April 6-7th June 21st, 28th Sept. 3rd Nov. West Huntspill 19th April 13th June 16th, 28th Sept. 8th Nov. 3.3 Seaweed Analysis Seaweeds were washed in distilled water to remove surface debris and the excess water shaken off prior to dissection. Fruiting bodies, bladders and seaweed tips (which have the potential to form reproductive tissue) were removed. The amount of growth in any one year is not clear, but it is thought to include two dichotomous divisions (Barrett and Vonge, 1958). Using this rule of thumb, light green (ie: newest growth) tissue was removed and chopped into thin strips using stainless steel scissors. Approximately 60-70g of material was chopped into glass jars and frozen until the analysis could be undertaken at the N.R. A/s. laboratory at Exeter. Seaweeds were either chopped.the same day or refrigerated overnight and chopped the following day. 4. RESULTS All results are presented in Appendix I and illustrated in Figures 2-4. Dichlorobromomethane was not recorded above the limit of detection (3|ig/kg) at any of the sites examined. Chloroform, dibromochloromethane and bromoform were recovered from seaweed tissues throughout the survey period. 4.1 West Huntspill 4.12 Chloroform Chloroform was recorded from sites in the vicinity of the West Huntspill outfall throughout the sampling period, the highest levels occurring at Burnham Slip and site B downstream of the outfall. During June and September, Burnham Slip exhibited the highest levels recorded from any of the 23 sites sampled (17.6|ig/kg and 19.6|ig/kg respectively). The most westerly site to have accumulated chloroform was Stolford during April (6.44|jg/kg). It should be noted that this was close to the detection limit of 6|ig/kg. During April all sites sampled between Stolford and Brean (site D) exhibited determinable levels of chloroform before the 1994 disinfection season was underway. 1 4.1 3 Dibromochloromethane Dibromochloromethane was recorded at three separate sites on three separate occasions during this study; Burnham Slip in June (6.78|ig/kg), Stolford in September (6.33|ig/kg) and Hinkley in November (6.5|Jg/kg).