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The intention to incinerate pelletised biosolids in the primary and secondary incinerator was forwarded in September 2006. SITA wrote to the Environmental Protection Unit of the Department of Local Government and the Environment to request an amendment to their Waste Disposal Licence WDL/06/2003/V1 to include Pelletised Biosolids from Meary Veg as conforming waste for incineration. Ref letter dated 28th September 2006, SITA-RG193letter.
The changes to the licence waste requested to allow a greater flexibility for the disposal of waste from the Island's sewage plant. Currently this material is stored on the island, and is being generated at approximately 35 tonnes a week. This material was previously been disposed of by spreading on the land but this practice has now stopped. The relatively high calorific value of the material makes it very suitable for incineration to produce electricity, especially in the secondary incinerator which where the waste has a low calorific value and uses a large amount of virgin gas oil to maintain a temperature of above 1000°C to comply with WID.
A trial period of 1 month is recommended to ensure that the monitoring of the incineration of the biosolids is viewed over an extended time, to show compliance with WID, as well as the Waste Disposal Licence. It is suggested a trial period starts on the 9th of July 2007 and follows the procedures and monitoring laid down in this procedure.
The new fuel is a new waste stream from the island's sewage treatment plant Meary Veg, and classified under the European Waste Category as EWC 19 08 05 - Wastes from wastewater treatment plants not otherwise specified - sludges from the treatment of urban waste water. The material is in the form of dried pellets of biosolid from the process.
Samples of the biosolid have been taken and analysed for main components, and calorific value:
From this analysis the parameters were used to determine if the material was hazardous. Since there is a high quantity of ammonium, phosphorus, and sulphur in the sample, the hazard assessment has been assessed on any formation of ammonium salts, phosphate salts, and sulphate salts. During the trial the pellets will be sampled twice weekly. The samples will be sent for analysis to a UKAS laboratory to determine heavy metal, NCV, sulphur and chloride content.
None of the parameters tested by the external laboratory exceeded these limits, therefore the material is classified as non-hazardous, and no safety datasheet is required.
The material is transported to site in polypropylene bags of 750Kg nominal capacity. The bags reduce the risk of spillage while being transported to site, and handling on site. The bags will be placed into the waste pit, in a designated bay to assist in the mixing of the material with other waste in the pit. This will give a better mixing of the waste instead of direct feed into the hopper.
If any spillage occurs it is most likely to occur during the moving of the bags off the delivery vehicle. When a spillage occurs it will be recorded using the site's Incident Reporting procedure, and the EPU will be informed if any impact to the environment has occurred or likely to occur. The spillage will be maintained inside the waste reception area, and coned off to prevent the spread of the material by other vehicle movement. The material will then be swept into the waste pit.
Any person who has responsibility for carryout this procedure will be instructed before the trial starts of their duties to ensure the trail operation is carried out as stated in this procedure and ensure compliance to WID condition and the Waste Licence conditions.
The material will be delivered onto site in 750 Kg bags for the primary. The bags will only be delivered when the plant is operation to prevent the excess storage of biosolids on site. During the trial any exceedances of the Waste Licence conditions will result in the feeding of biosolids being stopped. The delivery onto site will be 50 tonnes per week maximum.
The 750 Kg bags will be placed into bay 3 so that the mixing of the waste can be achieved or feeding of 1 bag an hour maximum into the hopper can be achieved.
On Monday and Friday samples of bottom ash, APCR and biosolid pellets will be taken for analysis. These samples will be sent to an external UKAS laboratory for trace metal analysis. The analysis of the biosolid pellets will also include, NCV, sulphur and chloride content.
Trace metal analysis will include: Mercury Cadmium Thallium Antimony Arsenic Chromium Cobalt Copper Lead Manganese Nickel Vanadium The dioxin cartridge for the continuous dioxin sampling will be changed for a new cartridge at the beginning of the trial, and changed at the end of the trial to allow an accurate dioxin emission analysis for the trial period.
If an incident occurs that exceeds our Waste Licence conditions, the actions identified in the Waste Licence will be followed, and the feeding of biosolids will be stopped. All incidents will be reported in the Shift Log, and in the trial report. The incident will then be investigated, and if the biosolids was the cause of the incident the trail will be halted until actions identified to prevent re-occurrence are completed. The outcome of the investigate and actions taken will be reported in the trail report.
When a spillage occurs it will be recorded using the site's Incident Reporting procedure, and the EPU will be informed if any impact to the environment has occurred or likely to occur. The spillage will be maintained inside the waste reception area, and coned off to prevent the spread of the material by other vehicle movement. The material will then be swept into the waste pit. During this operation the operative will wear the following PPE:
Hard hat Overalls Safety footwear Gloves Safety glasses Dust mask If there is an enquiry from the public regarding the trial are communicated to SITA, they will be informed of the nature and reasons for the trial.
During the trial period the following records will be maintained and printed out on a daily basis to show compliance to our Waste Licence and WID, and form part of the final report:
Delivered quantity of biosolids pellets Primary furnace temperature Steam flow NCV Continuous Emissions Monitoring Data Hydrogen Chloride Carbon Monoxide Sulphur Dioxide Ammonia VOC (TOC) Oxides of Nitrogen Particles Oxygen Water Flow rate The following records will form part of the final report: Analysis from the dioxin cartridge Bottom ash results APCR results Biosolid pellets results
Biosolid quality and quantity delivered during the trial period. The external analysis laboratory report and weighbridge data is available on site.
The total delivery of biosolids per week was below 50 tonnes/week apart from one week, which was just over at 50.1 tonnes. The quality of the biosolids remained consistent through out the trial.
| Date | Quantity Tonnes | Weekly total Tonnes |
|---|---|---|
| 10/07/2007 | 7.82 | 50.1 |
| 11/07/2007 | 8.42 | |
| 12/07/2007 | 8.66 | |
| 13/07/2007 | 8.46 | |
| 13/07/2007 | 8.42 | |
| 14/07/2007 | 8.32 | |
| 16/07/2007 | 8.26 | 47.02 |
| 17/07/2007 | 8.02 | |
| 18/07/2007 | 7.68 | |
| 19/07/2007 | 7.88 | |
| 20/07/2007 | 7.28 | |
| 21/07/2007 | 7.9 | |
| 23/07/2007 | 8.68 | 48.48 |
| 24/07/2007 | 8 | |
| 25/07/2007 | 7.88 | |
| 26/07/2007 | 7.58 | |
| 27/07/2007 | 7.94 | |
| 28/07/2007 | 8.4 | |
| 30/07/2007 | 7.38 | 45.8 |
| 31/07/2007 | 7.7 | |
| 01/08/2007 | 8.06 | |
| 02/08/2007 | 7.48 | |
| 03/08/2007 | 7.5 | |
| 04/08/2007 | 7.68 | |
| TOTAL | 191.4 | 191.4 |
The trends for furnace temperature, NCV and steam flow are available on site. The calorific value of the biosolids has remained consistent throughout the trial. Due to the consistent calorific value of the biosolid it is not likely that this material will effect the NCV and steam flow of the operation of the plant if mixed with the other wastes received on site and below a delivery of 50 tonnes a week. The furnace temperature was maintained above the waste licence requirement of $850^{\circ}\mathrm{C}$ throughout the trial, when waste was being incinerated.
| Sample Reference | 041/07 | 042/07 | 043/07 | 044/07 | 045/07 | 046/07 | 047/07 | 048/07 | 049/07 |
|---|---|---|---|---|---|---|---|---|---|
| Calorific value (MJ/Kg) | 18 | 18 | 16 | 18 | 18 | 18 | 18 | 18 | 18 |
| Sulphur (%) | 0.46 | 0.65 | 0.6 | 0.38 | 0.53 | 0.22 | 0.15 | 0.09 | 0.06 |
| Chloride (mg/Kg) | 840 | 800 | 720 | 600 | 920 | 840 | 520 | 1600 | 1000 |
| Antimony (mg/Kg) | <10 | <10 | <10 | <10 | <10 | <10 | <10 | <10 | <10 |
| Arsenic (mg/Kg) | 11 | 10 | 9 | 9 | 10 | 11 | 9 | 8 | 10 |
| Cadmium (mg/Kg) | 2 | 2 | 2 | 2 | 2 | 2 | 2 | 2 | 2 |
| Chromium (mg/Kg) | 47 | 44 | 38 | 41 | 46 | 47 | 42 | 38 | 42 |
| Cobalt (mg/Kg) | 20 | 15 | 18 | 19 | 15 | 20 | 13 | 19 | 15 |
| Copper (mg/Kg) | 1200 | 210 | 130 | 160 | 150 | 180 | 140 | 130 | 150 |
| Lead (mg/Kg) | 150 | 150 | 110 | 140 | 140 | 150 | 130 | 100 | 140 |
| Manganese (mg/Kg) | 230 | 200 | 270 | 200 | 190 | 230 | 160 | 250 | 190 |
| Mercury (mg/Kg) | <1 | 1 | 1 | 1 | 1 | 1 | <1 | 1 | 1 |
| Nickel (mg/Kg) | 42 | 37 | 37 | 43 | 39 | 41 | 36 | 39 | 36 |
| Thallium (mg/Kg) | <10 | <10 | <10 | <10 | <10 | <10 | <10 | <10 | <10 |
| Vanadium (mg/Kg) | 10 | 10 | <10 | <10 | <10 | 10 | <10 | <10 | <10 |
| Sample Reference | 050/07 | 051/07 | 052/07 | 053/07 | 054/07 | 055/07 | 056/07 | 057/07 | 058/07 | Min | Max |
|---|---|---|---|---|---|---|---|---|---|---|---|
| TOC (%) | 0.2 | 1.1 | 0.4 | 0.8 | 0.3 | 1.9 | 0.5 | 0.5 | 3.4 | 0.82 | 4.4 |
| Antimony (mg/Kg) | 56 | 54 | 66 | 60 | 57 | 91 | 99 | 81 | 76 | 26 | 260 |
| Arsenic (mg/Kg) | 12 | 15 | 11 | 17 | 11 | 14 | 14 | 17 | 13 | 5 | 41 |
| Cadmium (mg/Kg) | 11 | 7 | 11 | 6 | 11 | 14 | 10 | 7 | 10 | 1.8 | 25 |
| Chromium (mg/Kg) | 86 | 84 | 79 | 91 | 130 | 88 | 150 | 85 | 74 | 42 | 220 |
| Cobalt (mg/Kg) | 15 | 17 | 44 | 17 | 15 | 19 | 13 | 16 | 19 | 5 | 29 |
| Copper (mg/Kg) | 2300 | 7800 | 2400 | 1700 | 1700 | 7000 | 3000 | 12000 | 3800 | 313 | 20000 |
| Lead (mg/Kg) | 2200 | 3100 | 2000 | 1100 | 1600 | 1600 | 720 | 1400 | 1300 | 215 | 6500 |
| Manganese (mg/Kg) | 1200 | 1500 | 900 | 1000 | 840 | 530 | 920 | 900 | 790 | 235 | 1000 |
| Mercury (mg/Kg) | <1 | <1 | <1 | <1 | <1 | <1 | <1 | <1 | <1 | 0.02 | 6 |
| Nickel (mg/Kg) | 48 | 100 | 44 | 59 | 56 | 230 | 190 | 48 | 39 | 22 | 180 |
| Thallium (mg/Kg) | <1 | <1 | <1 | <1 | <1 | <1 | <1 | <1 | <1 | 0.9 | 25 |
| Vanadium (mg/Kg) | 27 | 28 | 27 | 29 | 24 | 25 | 28 | 28 | 24 | 20 | 96 |
The daily CEMS reports are available on site. There were excursions of waste disposal licence limits and notifications submitted to the EPU during the trial period. Listed below are excursions experienced and reasons for excursions.
There were no excursions of the waste disposal licence emissions limits relating to the incineration of biosolids.
The external analysis laboratory report is available on site.
The dioxin reading for the trial period was 0.107 ng/m³. This is slightly higher than the periodic dioxin emissions limit of 0.1 ng/m³. A contributing factor to this slightly high reading was the number of shutdowns and start up of the primary incinerator during the trial period due to repairs being carried out on the turbine.
The external analysis laboratory report is available on site. The min and max results taken from all the bottom ash reports sent to the EPU have been included to represent a comparison for the analysis obtained during the trial. The trace metals in the bottom ash are not likely to have occurred due to the incineration of biosolids.
| Date | Excursion | Reason |
|---|---|---|
| 12.07.07 | Sulphur dioxide and hydrogen chloride | On going problem, under investigation, not related to biosolids as chloride and sulphur content of biosolid is low |
| 14.07.07 | ||
| 15.07.07 | ||
| 19.07.07 | ||
| 21.07.07 | ||
| 28.07.07 | ||
| 29.07.07 | ||
| 05.08.07 | ||
| 06.08.07 | ||
| 07.08.07 | ||
| 08.08.07 | ||
| 28.07.07 | Oxides of nitrogen | Low levels of ammonia |
| 30.07.07 | Carbon monoxide | Plant trip caused by low water level in the boiler |
The external analysis laboratory report is available on site. The min and max results taken from all the APCR reports sent to the EPU have been included to represent a comparison for the analysis obtained during the trial. The trace metals in the APRC are not likely to have occurred due to the incineration of biosolids.
| Sample Reference | 059/07 | 060/07 | 061/07 | 062/07 | 063/07 | 064/07 | 065/07 | 066/07 | 067/07 | Min | Max |
|---|---|---|---|---|---|---|---|---|---|---|---|
| Antimony (mg/Kg) | 430 | 340 | 410 | 470 | 480 | 440 | 420 | 450 | 440 | 10 | 610 |
| Arsenic (mg/Kg) | 65 | 56 | 70 | 60 | 78 | 83 | 86 | 74 | 69 | 31 | 120 |
| Cadmium (mg/Kg) | 210 | 180 | 220 | 280 | 250 | 250 | 180 | 220 | 290 | 26 | 280 |
| Chromium (mg/Kg) | 57 | 51 | 54 | 74 | 58 | 50 | 42 | 63 | 53 | 25 | 110 |
| Cobalt (mg/Kg) | <10 | 10 | <10 | 12 | <10 | <10 | <10 | 10 | 12 | 5 | 19 |
| Copper (mg/Kg) | 460 | 390 | 450 | 530 | 490 | 470 | 400 | 450 | 670 | 215 | 540 |
| Lead (mg/Kg) | 4200 | 3800 | 4700 | 4200 | 4500 | 5200 | 4000 | 4100 | 5000 | 1480 | 5300 |
| Manganese (mg/Kg) | 300 | 270 | 300 | 350 | 290 | 260 | 240 | 320 | 310 | 193 | 55 |
| Mercury (mg/Kg) | 7 | 10 | 9 | 8 | 8 | 11 | 7 | 9 | 11 | 3 | 18 |
| Nickel (mg/Kg) | 24 | 23 | 24 | 33 | 23 | 21 | 18 | 28 | 24 | 17 | 54 |
| Thallium (mg/Kg) | <10 | <10 | <10 | <10 | <10 | <10 | <10 | <10 | <10 | 0.9 | 10 |
| Vanadium (mg/Kg) | 17 | 18 | 16 | 21 | 16 | 13 | 12 | 19 | 15 | 20 | 100 |
From the results of the biosolid trace metal analysis, and calorific value the biosolid would not adversely effect the emissions to ground, water and land from the Energy from Waste facility.
The excursions during the trial were caused by other factors; therefore the plant can incinerate biosolids and remain compliant to the site's waste disposal licence.
The incineration of 50 tonnes a week of biosolid would assist the island and provide a disposal route for a waste, which is currently being stock, piled.
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