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Title: UK Sewage Sludge Survey
Author: "A Gendebien
Author: C Carlton-Smith
Author: M Izzo
Author: J E Hall
Author: Environment Agency
Document Type: Monograph
Annotation: Environment Agency Project ID:EAPRJOUT_1053, Representation ID: 590, Object ID: 2326
Abstract:
OF DATA AVAILABLE 129 LIST OF TABLES Table 2.1 Total annual quantity of sludge disposed of to different outlets in the year of the survey (1996/7) in England and Wales 10 Total annual quantity of sludge disposed of to different outlets in the year of the survey (1996/7) in Scotland 11 Total annual quantity of sludge disposed of to different outlets in the year of the survey (1996/7) in Northern Ireland 11 Annual sludge production per works size in England and Wales (1996/7) 12 Table 2.5 Annual sludge production per works size in Scotland (1996/7) 13 Table 2.6 Annual sludge production per works size in Northern Ireland (1996/7) 13 Predicted sludge production Wales and disposal in 2005 for England and 14 Table 2.8 Predicted sludge production and disposal in 2005 in Scotland 14 Table 2.9 Predicted sludge production and disposal in 2005 in Northern Ireland 15 Table 3.1 Treatment of sludge (%) recycled in agriculture in England and Wales (1996/7) 17 Treatment applied to liquid sludge recycled in agriculture in England and Wales (1996/7) 19 Treatment applied to dewatered sludge recycled in agriculture in England and Wales (1996/7) 19 Future trends (by 2005/6) in treatment of sludge used in agriculture in England and Wales (%) 21 Table 3.5 Treatment of sludge (%) recycled in agriculture in Scotland (199617) 22 Table 3.6 Treatment applied to liquid sludge recycled in agriculture in Scotland (1996/7) 22 Table 2.2 Table 2.3 Table 2.4 Table 2.7 Table 3.2 Table 3.3 Table 3.4 R and D Project Record P2/065/1 iv Page Table 3.7 Table 3.8 Treatment applied to.dewatered sludge used in agriculture Scotland-( 1996/7)a in 23 Future trends (by 2005/6) in treatment of sludge used in agriculture in Scotland (%) 23 Table 3.9 Treatment of sludge (%) in Northern Ireland (1996/7) 24 Table 3.10 Treatment of sludge used in agriculture in Northern Ireland (1996/7) 24 Table 3.11 Future trends (by 2005/6) in treatment of sludge used in:agriculture in Northern Ireland (%) 24 Table 4.1 Quality of sludge,in England and Wales for main outlets 26 Table 4.2 Quality of sludge used in.agriculture-in 27 Table 4.3 Quality of sludge in Scotland for main- outlets 27 Table 4.4 Quality of sludge used in agriculture in Scotland in.1996/7 28 Table 4.5 Quality of sludge in Northern Ireland for main outlets in 199617 28 Table 4.6 a, Quality of sludge used in agriculture in 199617 in Northern Ireland ._I. 29 Table 5.1 Area of agricultural land utilised for-sewage sludgerecycling.in England and Wales 1996/97 32 Table 5.2 Utilisation 32 Table 5.3 Spreading method by land use in England and Wales (%) 34 Table 5.4 Average application rate .by application .method and land use in England and Wales (tds ha-a) 34 I Table 5.5 Land use for sludge recycling in Scotland (1996/7) 35 Table 5.6 Spreading method by land use in Scotland (%) 35 Table -5.7 Mean application rate by spreading method and landuse in,Scotland (tds ha-.a) 36 Area of agricultural land utilised for.sewage.sludge Northern Ireland (1996/97) 37 .a Table 5.8 1996/7 in England and.Wales of sludge application method (% of.area receiving sludge) Table 5.9 Spreading method employed in Northem.Ireland Table 5.10 Quality of agricultural recycling (1996/7) Table Awl Table AW2 soil used in.Northem Current and future sludge quantities.by Water. recycling in Ireland for sludge. 38 outlets (tds a-*), Anglian Annual sludge production by works size (tds.6I) Water (1996/7) R and D Project Record P2/065/1. a 37 (1996/7) 43 , Anglian .. i 43 Page Table AW3 Current and future treatment of sludge recycled in agriculture (tds a-a), Anglian Water 44 Current treatment of sludge sent to other outlets (tds a-a), Anglian Water (1996/7) 44 Sludge treatment according to works size (tds a-a), Anglian Water (1996/7) 45 Table AW6 Quality of sludge according to outlet, Anglian Water (1996/7) 45 Table AW7 Quality of sludge used in agriculture, Anglian Water (1996/7) 46 Table AW8 Land use and sludge application rate, Anglian Water (1996/7) 46 Table AW9 Spreading methods and application rate by land use: Anglian Water (1996/7) 47 Quality of agricultural Water (199617) 47 Table AW4 Table AW5 Table Awl0 Table NW1 Table NW2 Table NW3 Table NW4 Table NW5 Table NW6 Table NW7 Table NW8 Table NW9 Table NW10 Table NWWl Table NWW2a soil used for sludge recycling, Anglian Current and future sludge quantities by outlets, Northumbrian Water (1996/7) 49 Annual sludge production by works size, Northumbrian (1996/7) 49 Water Current and future treatment pf sludge recycled in agriculture, Northumbrian Water (tds a-a) 50 Current treatment of sludge sent to other outlets, Northumbrian Water (tds a-a) 50 Sludge treatment according to works size, Northumbrian (1996/7) (tds a-a) 51 Quality of sludge according to outlet, Northumbrian (1996/7) Water 51 Quality of sludge used in agriculture, (1996/7) Water Northumbrian Sludge application rate by land use: Northumbrian (1996/7) 52 Water 52 Spreading methods and application rate by land use, Northumbrian Water (1996/7) 53 Quality of agricultural soil, used for sludge recycling, Northumbrian Water (1996/7) 53 Current and future sludge quantities by outlets, North West Water (tds a-l ) 55 Annual sludge production by works size, North West Water (1995/6) 55 R and D Project Record P2/065/1 vi Page Table hIWW2b Table NWW3 Table NWW4 Table NWWS Table NWW6 Table NWW7 Table haww8 Tablea NWW9 Table ~XWWlO Table STWl Table STW2a Table STW2b Table STW3 Table STW4 Table STWSa Table STW5b Table STW6a Table STW6b Table STW7 Annual sludge production by.works size, North West Water. (1996/7) 55 Current and future tr-eatment for sludge recycled in -agriculture,~ North West Water (tds a-a) 56 Current treatmentof (tds a-a) 56 sludge sent to other outlet, North West Sludge treatment according to works size, North West Water (1996/7) 57 Quality pf sludge according to outlet,-North (1996/7) 57 West Water Quality of sludge used in agriculture, North West Water (1996/7) 58 Land use and sludge application rate, North West Water (1996/7) 58 Spreading methods and applicationrate, (1996/7) 59 Quality.of agricultural Water (1996/7) North West Water. .I soi and used for sludge recycling, North West 59 Current and future sludge quantities by outlets, Severn Trent Water (tds a-a) 61 Annual sludge production by works size, Severn Trent Water (1995/6) 61 .. Annual sludge production by works size, Severn Trent Water (1996/7) 61 Current. and future treatment of sludge recycled to agriculture, Severn Trent Water 62.. Current treatment of sludge sent to other outlets, Severn Trent Water. (tds a-r) 62 Sludge treatment according to works size, Severn Trent Water (1995/6) 63: Sludge treatment according to works size, Severn Trent Water (1996/7) 63 Quality of sludge according to outlet, Severn Trent Water (1995/6) 63 Quality of sludge according to outlet, Severn Trent Water (1996/7). 64 Quality of sludge used in agriculture, (1996/7) 64 R and D Project Record P2/065/1 vii Severn Trent Water Page Table STW8 Table STW 10 Table SW1 Sludge application rate by land use , Severn Trent Water (1996/7) 65 Quality of agricultural soil used for sludge recycling, Trent Water ( 199617) 65 Severn Current and future sludge quantities by outlets, Southern Water (tds a-l) 67 Annual sludge production by works size, Southern Water (1995/6) 67 Annual sludge production by works size, Southern Water (1996/7) 67 Current and future treatment for sludge recycled to agriculture, Southern Water 68 Current treatment of sludge sent to other outlets, Southern Water (tds a-a) 68 Sludge treatment according to works size, Southern Water (1995/6) 69 Sludge treatment according to works size, Southern Water (1996/7) 69 Table SW6a Quality of sludge according to outlet, Southern Water (1995/6) 70 Table SW6b Quality of sludge according to outlet, Southern Water (1996/7) 70 Table SW7 Quality of sludge used in agriculture, Southern Water (1996/7) 71 Table SW8 Land use and sludge application rate, Southern Water (1996/7) 71 Table SW9 Spreading method and application rate, Southern Water (1996/7) 71 Table SW10 Quality of agricultural Water (199617) 72 Table SW2a Table SW2b Table SW3 Table SW4 Table SWSa Table SW5b Table SWWl soil used for sludge recycling, Southern Current and future sludge quantities by outlets, South West Water (tds a-r ) 73 Annual sludge production by works size, South West Water (tds a-r) (199516) 73 Annual sludge production by works size, South West Water (tds a-r) (1996/7) 73 Current and future treatment of sludge recycled to agriculture, South West Water (tds a-l) 74 Table SWW4 Current treatment of sludge sent to other outlets (tds aa) 74 Table SWWSa Sludge treatment according to works size, South West Water (tds a-a) (1995/6) 75 Table SWW2a Table SWW2b Table SWW3 R and D- Project Record P2/065/1 . .. Vlll Page Table SWWSb Table SWW6. Table SWW7. Table SWW8 Table SWW9 Sludge treatment according to works size, South West Water (tds aa) (1996/7), 75 Quality of sludge according to outlet, South West Water (1996/7) 76 Quality-of (1996/7) 76 sludge used in agriculture, South.West.-Water Land use and sludge application rate, South West Water (1996/7) 77 a, Spreading methods and application rate, South-West Water (1996/7) 77 Table SWWlO : Quality of agricultural Water (1996/7) Table TWl Table TW2a Table TW2b soil used for sludge recycling, South West 78 Current and future sludge quantities by outlets, Thames Water (tds a-a ) 79 -a Annual sludge production by works size (tds a-a) , Thames Water (1995/6) 79 Annual sludge productionby (1996/7) 79 works size (tds-a-a) , Thames Water Current and future treatment for sludge recycled to agriculture, Thames Water (tds aa) 80 Table TW4 Current treatment of sludge sent to other outlets (tds a-a) 80 Table TW5a Sludge treatment according to works size (tds a-a), Thames Water (1995/6) 81 Sludge treatment according to works size (tds a-a), Thames Water (1996/7) 81 Table TW6a Quality of sludge according to outlet, Thames Water (1995/6) 82 Table TW6b Quality of sludge according to outlet; Thames Water (1996/7) 82 Table TW7 Quality of sludge used in agriculture, Thames (1996/7) 83 Table TW8 Land use and sludge application rate by -land use, Thames ,Water (1996/7) 83 Table TW9 Spreading method and application rate, Thames Water (1996M) 83 Table TW 10 Quality of agricultural Water (1996/7) 84 .a Table TW3 Table TW5b Table WWl, soil used for sludge recycling;Thames Current and future sludge quantities by,outlets, Welsh Water (tds a-a) R and D Project Record .P2/065/1 ix 85 Page Table WW2 Annual sludge production by works size (tds a-a), Welsh Water (1996/7) 85 Current and future treatment for sludge recycled to agriculture (tds a-a), Welsh Water 86 Sludge treatment according to works size (tds a-a), Welsh Water (1996/7) 86 Table WW6/7 Quality of sludge used in agriculture, Welsh Water (1996/7) 87 Table WW8 Sludge application rate by land use, Welsh Water (1996/7) 87 Table WW9 Spreading method and application rate, Welsh Water (1996/7) 87 Table WWlO Quality of agricultural Water (1996/7) 88 Table WW3 Table WW5 Table WXWl soil used for sludge recycling, Welsh Current and future sludge quantities by outlets, Wessex Water (tds a-a) 89 Annual sludge production by works size (tds a-a), Wessex Water (1995/6) 89 Annual sludge production by works size (tds a-a), Wessex Water (1996/7) 89 Current and future treatment of sludge recycled to agriculture (tds a-a), Wessex Water 90 Table WXW4 Current treatment of sludge sent to other outlets (tds a-a) 90 Table WXW5a Sludge treatment according to works size (tds a-a) , Wessex Water (1995/6) 91 Sludge treatment according to works size (tds a-a) , Wessex Water (1996/7) 91 Table WXW6a Quality of sludge according to outlet, Wessex Water (1995/6) 92 Table WXW6b Quality of sludge according to outlet, Wessex Water (1996/7) 92 Table WXW7 Quality of sludge used in agriculture, Wessex Water (1996/7) 93 Table WXW8 Land use and sludge application rate, Wessex Water (1996/7) 93 Table WXW9 Spreading method and application rate, Wessex Water (1996/7) 93 Table WXWlO Quality of agricultural Water (1996/7) 94 Table WXW2a Table WXW2b Table WXW3 Table WXW5b Table YW1 Table YW2a soil used for sludge recycling, Wessex Current and future sludge quantities by outlets, Yorkshire (tds a-a) Annual sludge production by works size (tds a-a), Yorkshire Water (1995/6) R and D Project Record P2/065/1 Water 95 95 Page Table YW2b Annual. sludge production by works size (tds a-r), YorkshireWater (1996/7) 95 Current and future treatment of sludge recycled to agriculture (tds a-a), Yorkshire Water 96 Table YW4 .: Current treatment of sludge sent to other outlets (tds a-a) 96 Table YW5a Sludge treatment according to works size (tds a-a): Yorkshire Water (1995/6) 97 Sludge treatment,according Water (1996/7) 97 Table-YW3 Table YW5b to works size (tds a-a), Yorkshire Table YW6a Quality of sludge according to outlet, Yorkshire Water (1995/6) 98 Table YWBb, Quality of sludge according to outlet, .Yorkshire Water (1996/7) 98 Table YW7 Quality-of 99 Table YW8 .. Land use and sludge application rate by land use, Yorkshire Water (1996/7) a- Table YW9 Spreading method employed, Yorkshire Table YWlO Quality of agricultural Water, (1996/7) Table. WoS 1 sludge used in agriculture, Yorkshire Water (1996/7) (1996/7) gg. .: 100 soil used for sludge recycling, Yorkshire 100 Current and future sludge quantities by outlets, West of Scotland (tds a-a) 103 Annual sludge production by works size, West of Scotland- a .. (1996/7) 103 Current and future treatment of sludge recycled to agriculture, West of Scotland 104 Table WoS4 Current treatment of sludge sent.to other outlets (tds a-r) 104 Table WoS5 Sludge treatment according.to works size, West of Scotland. (1996/7) 105 Table WoS6 a. Quality of sludge according to outlet: West of Scotland (1996/7) 105: TableaWoS7. Quality of sludge recycled to agriculture, West of Scotland (1996/7) 106 Table WoS8. Land use and sludge application rate, West of,Scotland (1996/7). 106 Table WoS9 Spreading. method and application rate, West of Scotland (1996/7). 106 -. Quality of agri cu It ural land used for sludge recycling, West of Scotland (1996/7) 107 Current and future sludge quantitiescby outlets, East of*Scotland (tds a-r) 109 Table.WoS2. Table WoS3 Table WoS 10 Table EoS 1 R and D Project Record P2/065/1 xi Page Table EoS2 Annual sludge production by works size, East of Scotland (1996/7) 109 Current and future sludge treatment for sludge recycled to agriculture, East of Scotland 110 Table EoS4 Current treatment for sludge sent to other outlets (tds a-a) 110 Table EoS5 Sludge treatment according to works size, East of Scotland (1996/7) 111 Table EoS6 Quality of sludge according to outlet, East of Scotland (1996/7) 111 Table EoS7 Quality of sludge recycled to agriculture, East of Scotland (1996/7) 112 Table EoS8 Land use and sludge application rate, East of Scotland (1996/7) 112 Table EoS9 Spreading method employed, East of Scotland (1996/7) 113 Table EoS 10 Quality of agricultural Scotland (1996/7) 113 Table EoS3 Table NoS 1 Table NoS2 Table NoS3 land used for sludge recycling, East of Current and future sludge quantities by outlets, North of Scotland (tds a-a) 115 Annual sludge production by works size, North of Scotland (1996/7) 115 Current and future treatment of sludge recycled to agriculture North of Scotland , 116 Table NoS4 Current treatment of sludge sent to other outlets 116 Table NoS5 Sludge treatment according to works size, North of Scotland (1996/7) 117 Table NoS6 Quality of sludge according to outlet, North of Scotland (199617) 117 Table NoS7 Quality of sludge recycled to agriculture, North of Scotland (1996/7) 118 Table NoS8 Land use and sludge application rate, North of Scotland (1996/7) 118 Table NoS9 Spreading method and application rate, North of Scotland (1996/7) 118 Quality of agricultural Scotland (1996/7) 119 Table NoS 10 Table NI 1 Table NI 2 land used for sludge recycling, North of Current and future sludge quantities by outlets, Northern Ireland (tds a-a) 123 Annual sludge production per works size in Northern Ireland (1996/7) 123 R and D Project Record P2/065/1 xii Page Table NI 3 Current and.future treatment for sludge recycled to.agriculture Northern Ireland (tds a-a) in 124 Table NI 4 Current treatment of sludge sent to other outlets (1996/7) 124 :-. Table NI 5. Sludge treatment according to works size in Northern Ireland (1996/7) 125 Table XI 6 Quality of sludge in Northern Ireland for main outlets .(1996/7) 125 Table NI 7 Quality of sludge used in agriculture in Northern Ireland (1996/7) 126 Area of agricultural land utilised for sewage sludge recycling in Northern Ireland (1996/97) 126 Table NI 9 Spreading method employed in Northern Ireland (1996/7) 127 Table NI 10 Quality of agricultural recycling (1996/7) 127 Table NI 8 Table -D 1 Tablea D2 soil used in Northern Ireland.for sludge Number of sludge centres and percentage of data supplied for the different parameters in each local area 131 Number of land units-and percentage of land sludged for which I data .was supplied for different parameters 132 LIST OF FIGURES. Sludge production, Figure 3.1 Major treatment processes of sludge recycled to agriculture in theUK (1996/7) 18 Type of agricultural (1996/7) 33 Figure 5.1 R and D Project Record,P2/065/1-- disposal and recycling in all regions (1996/97) 16 Figure 2.1 land utilised for sludge recycling,-all .. . Xl11 regions . R and D Project Record P2/065/1 xiv EXECUTIVE Production SUMMARY and dispqsal of sewage sludge The results of the UK survey of sludge production, treatment and disposal for the year 1996/7 are presented in two separate reports. On a national basis in R and D Technical Report.Pl65 and on a regional basis in this Project Record which.summarises the data for each water company in England and Wales, each region in Scotland,: and for Northern Ireland. The previous survey report carried out for. the then Department of the Environment for the year 1990/l, published in 1993, did,not include,information for separate companies so direct comparison between the two surveys cannot be made on a regional basis. The main regional findings from the 199617 survey data were as follows: ,Most sludge was disposed of by Thames Water (271 000 tonne. dry solids [tds] per annum) followed by Severn. .Trent Water (162 000 tds), North West Water (133 000 tds), Anglian Water (130 000. tds), Yorkshire.-Water (96 600 tds) and Southern Water (62 900. tds). The remaining four companies disposed of less than 40 000 tds each. Sludge-production is directly related to the population and the quantity of industrial effluent discharged in the catchment of the water company. These two inputs-are expressed in combination as population, equivalent (pe). Average sludge production on a per capita basis in the UK: is considered to be about 54gped. Fifty per cent of sludge was recycled to agricultural land and this outlet is usually considered to .be the BPEO (Best Practicable Environmental Option) where suitable land- is accessible. Welsh Water sent all of its-sludge to agricultural land and other companies making major use of the. outlet- were South West Water and Wessex Water (both 84%), Anglian Water (77%), Southern Water (65%) and Thames Water (53%). This reflects, the. extent of accessible farmland- available to these companies. Two companies made use of adedicated sitesa these were Anglian Water (13%.of sludge) and Severn Trent Water (14%). Dumping at sea accounted for 18% of sludge. disposed in England and.Wales. In terms of quantity, most was dumped by Thames Water (72 300 tds) and North West Water (59 400 tds) whilst the 19.500 tds dumped by..Northumbrian Water accounted for 50% of that companyas sludge. Theasea disposal outlet. has been used to take sludge from large conurbations on the coast without access to agricultural land. Legislation has stopped sea disposal at the end of 1998. An obvious alternative is incineration or. other thermal destruction process although this does not achieve complete disposal as an ash representing 30 - 40% of sludge dry matter is left which, if no use can be found for it, requires disposal to 1andfill:aIn 1996/7, incineration and landfill each accounted for 9% -of sludge production. These two outlets were most used by Severn Trent Water and Yorkshire Water, together taking about 50% .of sludge. production for these companies. Six per cent of sludge was used in land reclamation and for Thames Water, which made most use of land-reclamation, the outlet accounted for. 53 600. tds of. sludge or 20% of sludge disposed.. Where it is feasible, the use of sludge in land reclamation is an attractive agreena option making beneficial use of the soil building properties of sludge associated with its content of organic.matter-and slowly released-plant nutrients (nitrogen and phosphorus). Other R and D Project Record P2/065/1 1 outlets including awithin curtilagea, use in forestry or as compost accounted for 4% of sludge in England and Wales and are of local importance. Most sludge (59%) was produced at 119 large STWs with a pe of more than 150 000. Medium STWs (pe 10 000 - 150 000) numbered 475 and produced 33% of the sludge. Four per cent of sludge was produced at 881 small (less than 10 000 pe) STWs, most of which belong to Anglian Water (383), Wessex Water (149), Welsh Water (144), North West Water (54) and Severn Trent Water (37). The survey indicated an increase in sludge production in England and Wales from 968 000 tds in 199617 to 1 224 000 tds in 2005 (increase of 26%). This prediction seems high but is estimated on the basis of implementation of the UWWTD Directive. There will be little change for Anglian, Severn Trent and Thames Water but for the others, substantial increases in sludge production are predicted as waste water currently discharged to marine waters down outfalls has to be treated. The increases are: Northumbrian Water (119%), North West Water (30%), Southern (22%), South West (193%), Welsh (188%), Wessex (62%) and Yorkshire Water (38%). This extra sludge will be accommodated by use in agriculture (increase of 28%), treatment by incineration or other thermal process (increase of 324%) whilst the destination of 14% of the sludge in 2005 is classified as aothersa which in effect means undecided at the moment. In Scotland, the water industry made a major transition from local authority control to three water authorities in April 1996; namely North of Scotland, West of Scotland and East of Scotland. In 1996/7, Scottish water authorities relied heavily (76 %) on sea disposal although, as decreed in 1991, this has been phased out at the end of 1998. This is especially a problem in the West and East of Scotland which use the sea outlet for 93% and 52% of their sludge respectively. The other favoured outlet in 1996/7 was agriculture taking 19% of sludge altogether but 84% of sludge in the North of Scotland area. Landfill was a minor outlet for sludge in Scotland (4% total) although 4900 tds sludge (16%) was dumped in landfill by the East of Scotland water authority. The West of Scotland water authority sent 1200 tds of sludge to land reclamation. There was no incineration of sludge in Scotland in 1996/7. In Scotland, the majority of sludge (75%) was produced/treated at a limited number of large works (Table 2.5). North of Scotland water authority had no large STW but 41 of the 58 small STW in Scotland, the rest being with East of Scotland water authority. The quantity of sludge for disposal in Scotland is expected to increase to 198 000 tds by 2005 which would be 41% more than in 1996/7. At the time of the survey, reports in the media E. coli 0157 food poisoning outbreaks and unregulated landspreading of abattoir wastes, although unconnected with sludge recycling, had led to a negative public perception of sludge use in agriculture, leaving the water authorities undecided about their future sludge management. However, the data collected during this survey seemed to indicate that by 2005 agricultural recycling will still remain the favoured option for the North and East of Scotland Authorities while West of Scotland Authority is planning to divert most sludge towards energy recovery. East of Scotland is also looking into other outlets such as land reclamation. The water executive in Northern Ireland is divided into four divisions; Western, Eastern, Northern and Southern divisions. In Northern Ireland, in 1996/7, the total quantity of sludge R and D Project Record P2/065/1 2 amounted to.32 000 tds:Fifty. five percent of. sludge was recycled to agriculture and 45%.was disposed to sea. The majority of sludge (65%) was,t.reated at medium sized works. The Western Division recycled sludge mainly to agriculturea and. had no sea disposal. -The Southern Division also reported recycling most sludge to agriculture. .The. Northern Division still relied heavily.on sea disposal due to.the limited availability of suitable agricultural land.. The Eastern Division also relied ,mainly on sea disposal while -20% was. recycled to agriculture. It is estimated that the quantity of sludge produced. in the province will increase by 40% to around 44 000 tds by the year 2005. Northern Ireland has planned to redirect sludge currently dumped at sea as well as the increased production mainly to incineration. Agriculture will, a however, continue to.be a main outlet in the Western and Southern Divisions where storage facilities will be upgraded. Treatment of sludge used in agriculture . Twenty two per cent of-sludge used in agriculture in England and ,Wales was untreated; those. making most -use of untreated sludge were.,Anglian Water (54%), Wessex Water (43%).and Yorkshire water (28%). The use of untreated sludge in agriculture- is likely-to be associated with small STWs in. rural areas close to ~farmland.: Some farmers prefer- untreated sludge because -it contains more organic matter than some treated sludges. Fifty seven per. cent of sludge was treated by mesophilic-anaerobic digestion before landspreading, the next most used treatment process being storage of dewatered sludge cake (11%). At least 60% of sludge used in agriculture was liquid. It was estimated that by 2005, the use of untreated sludge in agriculture will have ceased, 46% of sludge will beatreated by:mesophilic anaerobic digestion and 37% willreceive a ahigh levela pasteurisation treatment a process including 18% which will -be thermally :dried. :,The latter process can be applied to stabilised or unstabilised sludge and produces a dry product aof about 90% ds.in the.fonnof granules or pellets. The process minimises the volume ofsludge .for disposal and the product.gives to operator flexibility since it can be stored;used on the land or as fuel or sent to landfill as circumstances require:, In Scotland, in 1996/7; 22% of sludge recycled in agriculture was untreated, 31% was stored as unstabilised cake and 15% stored aas liquid sludge. Thirty three percent of sludge was anaerobically- digested;- 11% liquid sludge and..22% followed. by dewatering. Fifty three percent of sludge recycled in agriculture was dewatered. In the future in Scotland there is still some uncertainty regarding treatment .options (18% classified as other) but thermal drying is expected to treat up. to 57% of the total quantity of. sludge going to agriculture by 2005/6; while anaerobic digestion will decrease substantiallya, down to less than 10%. Thermal drying is also expected to treat a large proportion of sludge used in other outlets such as for power generation in the West of Scotland Water-Authority. In Northern Ireland in 1996/7,-all sludge recycled in agriculture was treated to some degree, varying from mesophilic anaerobic digestion (51%), liquid storage (24%) or cake storage (25%). Seventy-five per cent of sludge used in agriculture was liquid. R and D Project Record P2/065/1 Future strategy for Northern Ireland is still being developed, however, it was indicated that sludge from Belfast will be incinerated and at least 75% of the sludge recycled to agriculture will be treated by mesophilic anaerobic digestion. Sludge and soil quality and application to agricultural land Sludges recycled to land were low in PTE content and soil analysis for PTEs where sludge had been applied gave results close to background levels. The total area of land to which sludge was applied in 1996/7 in England and Wales was 73 000 ha which was less than 1% of the total area of agricultural land. It covers around 16 000 land units (areas of land receiving sludge) some of which were being treated several times that year. Fifty-nine percent of the area treated with sludge in England and Wales in 199617 was arable land. There were regional differences in the proportions applied to arable and pasture and between surface application and injection, reflecting climate, local agriculture and sludge treatment practice. Sludge was predominantly applied to arable land in most regions except in Welsh and North West Water, where pasture represented up to 80% of the area receiving sludge. The larger areas used for sludge recycling (more than 10 000 ha per annum) were located in Thames Water, Severn Trent Water, and Anglian Water. The most common spreading method was injection to plough depth which was used for 57% of sludge applied to land. It was the main method of application in Anglian Water, South West Water, Thames Water and Wessex Water. For Northumbrian Water, Welsh Water and Yorkshire Water, the splash plate was the most used method of application. In these companies, liquid digested sludge was the main type of sludge used in agriculture. The average application rates of sludge in England and Wales was 3.4 tds ha-! for arable land and 2.9 tds ha-i for pasture. The total area of land to which sludge was applied in 1996/7 in Scotland was 4200 ha. This includes around 600 land units divided between arable (67%), and pasture (33%).The most common spreading methods were splash plate and injection to plough depth both for arable and pasture land. The average application rates of sludge for 1996/7 was 3.9 tds ha-a for arable land and 1.9 tds ha-a for pasture. The total area receiving sludge in 1996/7 in Northern Ireland was 1200 ha. Application rates were only supplied for the Western and Southern Divisions. In the Western Division, spreading rates were in the range of 8.6 tds ha-a of dewatered sludge, while in the Southern Division, the rate of application was an average of 1.9 tds ha-a for liquid digested sludge and 2.2 tds ha-r for liquid stored sludge.
Publisher: Environment Agency
Subject Keywords: Disposal; Survey; Quality; Sewage sludge; Production; Treatment; Regional
Geographic Keywords: United Kingdom
Extent: 150
Permalink: http://www.environmentdata.org/archive/ealit:4812
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