The wild winds of change

The waste management industry has entered a period of significant change with the onset of the Landfill Directive. Previous legislative change has had only limited impact on the daily operations of a treatment plant; the Directive is set to change all that.

Environment Agency research on leaching tests, conducted in the mid 1990s, indicates that there may be a general problem in meeting the standards for a hazardous landfill site. Whilst the most recent (and probably final) landfill acceptance criteria publication from Brussels allows, in certain circumstances, up to three times higher limit values for specific parameters, this will be subject to prior approval from the competent authority.

Leachate quality

In all cases, the characteristics and surroundings of the receiving landfill site will be taken into account, demonstrated by the completion of a suitable risk assessment. Furthermore, there will certainly be far fewer landfill sites permitted to accept hazardous waste by 2005 (predicted numbers vary). Meeting current landfill acceptance criteria is relatively straightforward, however, by 16 July 2005 we have a different set of criteria to meet – leachate quality.

The Empire Waste Treatment Facility in Aldridge, run by Onyx Environmental Group, is one of the UK’s largest inorganic chemical waste treatment plants and one of very few accredited with both quality and environmental standards (ISO 9001 and ISO 14001).

Situated in the heart of the industrial Midlands, it has a capacity to process in excess of 250,000 tonnes of waste each year. Significantly, the treatment processes generate more than 36,000 tonnes/yr of filter cake, which is disposed of to one or more of Onyx’s licensed landfill sites.

A number of initiatives are already underway at the Aldridge site. Firstly, way back in the pre-landfill tax days, Onyx decided to replace the existing, manually operated, Johnson Progress filter presses with modern, efficient, fully automated units. However, the landfill tax water-discounting scheme put paid to that, as the financial benefits were greatly reduced – until now.

Filter cake quality

In December 2002, three gleaming, fully automatic Edwards & Jones filter presses were commissioned. Housed in a new building, the presses have a total capacity 30 per cent greater than the previous units and can be operated by a single person.

The biggest bonus has been the quality of filter cake produced, having a water content more than five per cent lower than previously achieved. Additionally, there is a three-fold reduction of suspended solids in the resultant aqueous effluent – quite staggering for conventional plate and chamber filter presses and well worth the considerable investment.

The reduced volume of filter cake is very significant, particularly if additional treatment is required in order to meet the landfill acceptance criteria. Our scientists are analysing hundreds of samples of filter cake as well as other waste residues currently disposed of to landfill. Many of the analytes being tested are new to our plant laboratories, requiring further investment in analytical equipment. It is imperative that we fully understand our position, well in advance of the published deadlines so that we are able to meet the needs of our customers.

Safe disposal

The Onyx Environmental Group is a specialist in waste stabilisation/solidification techniques. One such technique is the cement-based Ashrock process, widely used in France and being considered for introduction in the UK. This process utilises the cementitious properties of APC (air pollution control) residues, cement and other additives to stabilise the hazardous properties of wastes, allowing the resulting solid mass to be disposed of in a separate cell in a non-hazardous landfill site.

If we draw the same conclusion as the Environment Agency and filter cake does require additional treatment prior to landfill, the Ashrock process will come into its own. Not forgetting, of course, the tens of thousands of tonnes of APC residues generated from waste incineration each year and currently going to landfill, much of which has undergone little or no pre-treatment. It is unfortunate that we have had to wait almost to the 11th hour for politicians to provide the industry with the necessary guidance to enable us to plan for these changes.

Exciting times are ahead, I’m sure.