Rhone Poulenc - Staveley Site - Tank Cleaning
SITE: Rhone Poulenc - Staveley Site, Staveley, Derbyshire.
- Tanks number 1 and number 33 had the majority of crude benzole residue removed and transported by road tanker to be disposed of through an off site treatment plant. Each tank then was left with approximately 1 metre in depth of residue in each tank. The tanks were cleaned using the Chemiphase biological process in order to ensure the tank met the “clean standards” as outlined.
- There were 8 tanks to be cleaned. Each tank 12, 11, 10, 6, 4, 1, & 33 had new specially adapted manway covers fitted, incorporating a 3” valve and inlet pipe of approximately 9 metres in length feeding to the tank base. This pipe would enable the tanks to be bottom pumped, filled under pressure in order to create a vortex, which would displace the Benzene Sludge from the tank base and also oxygenate the waters and so create an ideal environment for bacterial growth.
- Tank 34 was part of the site scrubbing system, which had to be upgraded by Chemiphase. The up-grade involved the addition of a Carbon Filtering System to a Scrubbing Vapour System which was then inter connected to all of the tanks requiring treatment. Monoethanolamine was also added to neutralise any acidic gases evolved. A specialised chemical manufactured by the Group called ODOURSOLV was used to ensure all malodours were reduced to the absolute minimum.
- Water extracted from the Local River was used to fill all Tanks to approximately 2 Metres above the level of Solids. Additions of Peroxide were then added to oxidise all of the cyanide complexes present to the carboxylic group ions. Once this was achieved a cleaning additive (CITRASOLV) was introduced to each of the tanks. The dosage rate for the Citrasolv product was approximately 2,500ppm. Citrasolv is a citrus blend of biodegradable solvents with a fragrant aroma. CITRASOLV will disperse most medium to heavy oil and tar compounds effectively.
- Once the citrasolv product was added, each tank was re-circulated for 36 hours to allow the product to fully contact all surfaces and soak into all deposits present.
- Each tank was then filled to approximately 50% of its total capacity using more water from the local river via the existing hydrant service. Once filled each tank was then re-circulated. The re-circulation process was essential for it would avoid any solids settling in the tank, the circulation would transport all of the nutrients required to maintain a healthy environment for the bacteria species added and also it was a good method for ensuring the correct level of oxygen was present in order to support life i.e. allowed the biomass to be continually oxygenated.
Specialised strains of bacteria with the capability of degrading a variety of organic chemicals including Benzene, Toluene and Xylene were introduced. This process would then take between 2-4 weeks in order to fully degrade all solids to the acceptable level. Each tank was then regularly tested until the optimum level of degradation was achieved.
- The only deposits remaining in each of the tanks was a mixture of Iron Compounds and any heavy metals collected through the processes relating to Crude Coal processes.
- Once the tank was empty. A final rinsing programme using Water extracted from the local river along with the addition of our product Citrasolv was implemented. All aqueous waters were then be collected in Tank 11 and then pumped to the vitox effluent plant for final polishing prior to being discharged to sewer.
- Again a testing regime to monitor the effectiveness of the procedure was implemented. This ensured all components of the treatment programme were maintained at the required levels to maximise treatment performance.
- As the tanks were finally washed and drained of aqueous liquids. Each tank was then Gas checked prior to entry of personnel.
- Finally each tank was opened and the metal deposits were removed and placed into skips. This was then sampled and analysed to determine its composition. The analysis was sent to several land-fill sites for approval. Once approved, the material was loaded onto lorries for disposal to a licensed landfill site.
Chemiphase on-site personnel carried out all of the analytical tests at regular intervals and provided comprehensive reports on a regular basis.
Parameters analysed included:
pH, T.D.S, C.O.D. Oxygen. Cyanide, Methane, Total Sulphates, Phosphates, Biomass, D.O.U.R. (Measurement of Respiratory Rate for Bacteria), Total Organic Levels, B.T.X and Nutrient concentration.
The Work Completed
To date tanks 1, 33, 12, 11, 10, 6, 4 have all been cleaned, and the Iron deposits have been approved by all bodies concerned, transported to a land fill site that had been audited by Chemiphase, and Rhone Poulenc. Through this project, we have been able to biologically degrade around 550 tonnes of “nasty organic’ coal derivatives!! Treat 1300 tonnes of effluent before discharging through the vitox unit on site and clean out and dispose of 150 tonnes of principally Iron deposits that was left in the tanks after the degradation process.