Getting domesticated

There are myriad choices when specifying a package treatment plant. Steve Gibb and Tim Mackley of Balmoral Tanks outline some of the latest developments in the technologies and legislation

Treatment of wastewater from small domestic sources has come a long way since the introduction of septic tanks. As well as process development, performance demands from customers and requests for simplicity of design from installers have driven the improvements now widely provided by package treatment plant (PTP) manufacturers. These include:
  • High effluent constituent removal
  • Uncomplicated installation
  • Reliable, simple operation
  • Ease of maintenance
  • Odour reduction
Today's PTP specifier can choose from a multitude of designs utilising a variety of processes including fixed film and suspended growth with both aerobic and anaerobic biology. It is not just the processes that are becoming more updated, the whole design of package plants is being altered to accommodate an ever-changing market and new legislation.

Adjustable turret heights allow for a variety of invert depths to suit different installations and low power requirements mean cost-effective systems. Systems are also getting shallower in design to accommodate high ground water and bedrock sites while also minimising excavation and backfill requirements.

The introduction of BSEN 12566 Pt3 in July 2008 will also require package plants to be fitted with an alarm system, something that has not been common on small package plants. By including this mandatory requirement within the new standard, the monitoring of plants will be improved across the whole market while removing cost differentials between manufacturers.

Shock tests
Other positive aspects emanating from the new standard relate to the accommodation of real-world test conditions for plant design. Once the plants have completed a start-up period, designed to establish bacterial cultures, they are subjected to a variety of shock tests. These include no flow, 50% flow, overloading and power failure.

Especially important for small plants, for example single household, these simulations provide a much more realistic understanding of how plants accommodate fluctuations.

It is likely that new designs will reflect these requirements with better surge control during peak flows, and the ability to accommodate loading variations.

One of the common materials of construction for modern PTPs is polyethylene (PE), a thermoplastic which is easily shaped through the use of a rotational moulding process.

PE offers a number of advantages to the modern builder including high impact resistance and robustness during yard handling and installation.

It is widely recognised within the rotational moulding industry that PE in its natural state offers optimum performance in terms of material properties. For this reason, a leading PTP design and manufacturing company, Balmoral Tanks, will make the move from pigmented PE to natural over the next few months.

Balmoral's entire PTP range will change in colour from a green pigmented mix to that of natural PE, resulting in improvements to its existing range while becoming an integrated design feature of products currently under development.

Moulding process
Balmoral's R&D department was busy during 2006 developing a new moulding process, which allows full structural baffles to be fused within PE vessels at the moulding stage. This process has far-reaching applications across the company's portfolio because it will allow single-piece tanks to be produced showing significant increases in manufacturing productivity and product performance by providing separate compartments for process requirements.

Advances within the moulding process have also reduced cycle times within the post moulding area of the PTPs. The use of this technology on future Balmoral wastewater treatment products also ensures complete conformity to BSEN 12566 Pt3 under its structural and water tightness tests.

In meeting the challenge to attain high-quality effluent from domestic PTP, end-users must also play their part. And this involves a programme of commissioning and maintenance to ensure their plant continues to operate at its full potential.

Professional installation, commissioning and servicing is now considered as important as the initial sizing and specification of a PTP. If these requirements are overlooked, for whatever reason, there is a high probability that the plant will eventually malfunction and this can often be prevented.

Recognising their responsibilities as the sewage treatment market evolves, manufacturers are improving their commissioning and maintenance services to ensure that full support is available throughout the product's life-cycle. Annual servicing ensures a long-lasting, efficient and reliable system which is capable of delivering continuous high-quality performance.

This positive change in market ethos has been underpinned by bodies such as British Water, which recently established a service training scheme for accreditation of engineers, and the updating of the Environment Agency's Pollution Prevention Guidelines Pt.4.

Balmoral Tanks has embarked upon a strategic alliance with PTP maintenance company Serious. This new partnership has created the opportunity for Balmoral to focus resources on developing its products, while commissioning and maintenance services are carried out by a professional and dedicated team across the country.

House-building boom
The house-building boom in Ireland is showing no sign of slowing down. But people are tempted to cut corners by specifying unfit-for-purpose WwTWs as they are buried out of sight. This, though, should not be a case of out of sight, out of mind because improperly specified WwTWs will come back to haunt the homeowner, the builder and the installer.

End-users are not being offered consistent advice on their requirements by their local authorities. It is clear from studying the building regulations that an update is required as a matter of urgency. Local authorities must take an active role by providing building control officers to oversee the installation of environmental units and ensuring completion is carried out according to planning legislation.

All prospective purchasers of WwTWs should request identification documentation from the manufacturer or agent. Proof of purchase, a warranty schedule, commissioning certificate and a maintenance contract for their plant is also essential to comply with planning legislation and the sales of goods or consumer acts.

Balmoral site engineers provide a commissioning certificate detailing all aspects of the installation. This form provides added value for specifiers and homeowners as it states the installation has been properly completed, and also supports the specifiers' records for professional indemnity insurance. If the plant has not been installed according to the manufacturer's instructions, the engineer will note this on the form.

Balmoral has been actively involved in the Irish sewage industry since 1996. Its systems are light and robust, making them easy to install. And its agents attend product-specific training courses to attain Balmoral authorised engineer status. The company views this as vital, particularly with regard to health, safety and environmental issues.

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