Introduction to the Vermitech System

Vermitech has developed a proprietary continuous flow system utilising a raised bed reactor design comprising:

Raised Beds: The core of the technology is an open-top reactor vessel (bed) in which the worms are housed.  The beds can be up to 40m long.

Mixing and feeding equipment: A controlled blend of biosolids is fed to the surface of the bed on a regular basis. The worms consume the waste in-and-around the top region producing vermicompost. Preparing the waste to make it worm accessible has required the development of mix formulae, mixing systems and mechanisms for spreading the material onto the surface of the bed. 

Worms are resident within the bed: The earthworms stay within the bed until they die, although a small percentage are lost during harvesting operations. In industrial systems, life expectancy is approximately 2 years, at which time they are removed from the base of the bed and form part of the fertiliser. Being a natural, non-agitated process, environmental impacts (including odour) are extremely low.

Harvesting: The vermicompost is removed from the base of the bed, using equipment developed by Vermitech that “cuts” the bottom layer from the bed via a specialist bed base design and deposits it upon a conveyor belt. This occurs on a time frequency basis and the depth of cut is controlled via an adjustable cutting head.

Drying and Screening for despatch: In keeping with the natural approach of the technology, harvested material is air-dried, screened to correct size and sold following a quality assured testing process.

Worms maintain the eco-system balance: Having much in common with other biological treatment (e.g. activated sludge), the earthworm system retains a population balanced to the incoming food, increasing up to the point of food and space constraints. Although extremely flexible and robust, it is essential for the consistent productivity of the system that process control is maintained and that feedrates are matched to population and other environmental parameters

Benefits of the Vermitech System

The Vermitech System is a technology driven solution that is based on natural processes.As such it offers a unique blend of technical, economic and environmental benefits:

• Reliable – process control Quality system ensures repeatable results

• Minimal dust, odour and noise emissions

• Reduced greenhouse gas emissions compared to landfill

• Reduced trucking – the absolutely minimal use of amendments reduces trucking load over conventional composting

• Pleasant, attractive end-product with proven agricultural value

• Cost effective – whole of life costs are competitive with other biosolids treatment and remediation processes

• Scaleable to different size facilities producing a few tons per week through to large scale installations producing 100-200 tons per week

Quality Control

The Quality System is based on the principles of HACCP (Hazard Analysis Critical Control Point) program in accordance with the internationally recognised Codex Alimentarius Method of the World Health Organisation. HACCP is a management system that is designed to:

• identify potential hazards,

• nominate preventive measures to stop them occurring,

• monitor these areas and

• formalise action plans if a hazard is identified (in combination with plans to prevent reoccurrence).

HACCP programs represent standard practice for the Food Manufacturing Industry. Vermitech adopted the system after consultation with Australia’s major grocery chain, which having inspected Vermitech’s processes, endorsed the use of biosolids-based vermicompost by their farmer-suppliers (of fresh produce) subject to its production being quality assured.

It is for these reasons that the HACCP is being adopted in the new United Kingdom regulations regarding biosolids management programs.The benefits of utilising a HACCP based quality management system for Biosolids processing are multiple. HACCP is:

• A preventative system which moves from reactive quality control to pro-active quality assurance

• Targets resources at the most critical parts of a process

• Defines process parameters closely and assigns responsibility for monitoring

• The following flow diagram demonstrates the key elements of the system.

The following flow diagram demonstrates the key elements of the system

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The System Elements

Biosolids Capacity

For each facility, the system design is tailored to treat biosolids of the particular quality and quantity. The System receives input of dewatered biosolids cake from an upstream sewage treatment facility. The input biosolids are checked regularly for characterisation purposes and to monitor long-term trends. Test results are entered into a database. In addition, an assessment of the material will be made taking into account the following parameters:

• Moisture content

• Biosolids condition

• Ambient, bed and other process conditions

Feeding

The feeder system provides opportunity for biosolids to be mixed with a small amount of hard greenwaste, as a structural agent rather than a composting or diluting agent.

The exact feedrate is dependent upon a number of process control conditions:

• Current Bed loading and process conditions

• Production rate required

• Earthworm conditions

Since biosolids increase the temperature within the reactor, process parameters must be maintained within specified limits for the worm population.The specialized feeding equipment “cuts” the required depth of biosolids mix and delivers it onto a belt, which then runs the length of the bed. All operations are controlled by handheld remote. Speed and other parameters are adjustable to ensure an even depth and consistency.

This guarantees that the beds are not over or underfed. The process control requirements for these activities are described in Operations and Maintenance procedures and in the training provided by, Vermitech.

Processing

As the new feed source is established, the beds are monitored for parameters such as worm population and distribution, moisture content, bed temperature, etc.

These data are used to determine the requirements for any additional process control measures (e.g. feed rate and frequency). Regular audits (both qualitative and quantitative) of worm population and health are undertaken.

The beds act as a plug-flow type unit, residence time in the beds varies slightly in relation to feed rate.

Harvesting and Retrieval

The specially designed bed bases support the bed contents but also allow access for the custom-built harvesting device.  Harvesting depth is controlled via adjustable cutting teeth.

The harvesting apparatus contains variable speed drives for flexibility of operations.

The facility incorporates a collection belt system onto which the material is harvested. The belt system (extracted from one end of the bed) discharges the material, which is then taken for further processing.

Storage and Handling

After harvesting the material is still moist but has been processed to a stable, humus-like material by the vermicompost process.

The vermicompost is dried and screened. After this step, it is transferred into Quarantine pending results of testing.

Testing and release

The vermicompost will be batched in the Quarantine step and tested for compliance with the relevant standards.

The vermicompost is then stored before being dispatched to its eventual end use application.