Cleaning oil-contaminated soil at the Avenue This presentation can be used to introduce the activities on testing soil samples, removal of soil contaminants, bioremediation of soil and the thermal treatment of soil. It sets the scene by describing how soil is decontaminated at the Avenue.

The Avenue Coke Works Processed coal to produce coke Coke used as a smokeless fuel and in the steel-making industry Wastes from the process left behind when the works closed in 1992 The Avenue Coking works was built in the 1950's. Its main purpose was to treat coal to produce coke. This is a form of solid coal. Coke can be used as a smokeless fuel to heat houses or in the steel-making industry. The site also produced tar, benzole and sulphuric acid as by products of the process. This was a heavy, industrial process and it produced a lot of waste materials. Some were dumped on the site and others just contaminated the ground that the buildings stood on. The works closed in the 1992 and the clean-up process started in 1999.

Treating oily waste One of the worst problems is the tar-like waste that has been dumped into large ponds or lagoons. This is a thick, oily material that contains contaminants such as phenols, benzene and other hydrocarbons. The only feasible way to treat this material is to dig it out and destroy the contaminants at high temperatures. This process happens in the Thermal Treatment Unit. Oily waste was just dumped into big ponds or lagoons The waste needs to be dug out and treated

Thermal treatment plant Thermal treatment is the most important process on the site. It deals with the very heavily contaminated materials. It is also the most visible activity to those living around the site. The plant takes contaminated soil and removes the oily-contaminants. These are burned off to produce mostly carbon dioxide and water. Treat soil contaminated with oily substances Burns them off to leave mostly water and carbon dioxide

Thermal treatment Contaminated soil is dug out of the lagoons. In this form it is too thick and oily to go into the thermal unit, so it is mixed with soil that has previously been treated. This mixture is analysed to make sure that it is the correct consistency before being taken to the thermal treatment unit. Heavily contaminated soil is mixed with processed soil Gives soil of the correct ‘stickiness’ to go into the thermal treatment plant

Thermal treatment plant In the thermal treatment unit, soil is loaded into a large, rotating ‘oven’. This is called a rotary kiln. It heats the soil to around 600ºC. The contaminants are turned into gases, which are collected and treated, leaving clean soil behind. This process is called thermal desorption. Clean soil is cooled and sorted for re-use. Soil enters a rotary kiln (rotating oven) Heated to 600oC Contaminants driven off as gases Cleaned soil is cooled for re-use

Thermal treatment plant Any dust is filtered out of the gas and it is then burned at 1200ºC. This destroys contaminants and the main products of this process are carbon dioxide and water. The plume that can be seen coming out of the chimney is steam. Gases are collected Particulates filtered out Gases burned at 1,200oC Products are mostly carbon dioxide and water

Thermal treatment plant Once the plant has reached its operating temperature, it needs to run 24 hours a day, seven days a week. The Thermal treatment plant will run for two years and treat around 270,000 cubic metres of soil. That is enough to completely cover a football pitch with a pile of clean soil, 54 metres high. 24 hours a day, 7 days a week 270,000m3 of soil Cover football pitch with a pile 54m high