Brisbane adopts NuSewers technology

June Cummings reports

The eyes of the nation's major waste water authorities are directed at Brisbane's new sewerage technology, following the launch by Brisbane Water of its NuSewers design and construction concept, for all new sewerage works.

NuSewers took five years to test and trial in collaboration with industry before specifications were finalised and the clean sweep use of new age technologies was introduced.

Like most authorities, Brisbane Water found that its annual maintenance budget was fast approaching the cost of new sewerage works.

Lumbered with an ageing gravity sewer system, characterised by cracked pipes, joint failures, tree root penetration, faulty property connections, sewer chokes, overflows and penetration from stormwater and groundwater, Brisbane Water sought an innovative solution.

The vision was for a low maintenance, tree root free system. New technology was at an advanced stage.

Camera down sewer

Breakthroughs in pipeline inspection and maintenance technology, have made traditional sewer design and operation redundant. Jet-rodding equipment and closed circuit television (CCTV) and digital cameras have replaced the man down the sewer pipe cleaning and survey work. With most of this work carried out at the surface, small diameter maintenance shafts are replacing man entry holes.

The new inspection and maintenance process now makes it possible to lay both horizontal and vertical bends in the system without complicated joints, further minimising the number of access structures.

Importantly, pipes and fittings made from polyethylene offer a fully-welded system with fewer joints virtually eliminating infiltration of the main system.

With the rapid expansion of Brisbane's population, green field suburbs such as Forest Lake, presented Brisbane Water with an ideal trialling and testing laboratory for its visionary new technology system.

Large radius bends

Working with industry, Vinidex Sewertech polyethylene (PE) pipe was selected as the r&d material for NuSewers pipelines. Its advantages are the pipe is flexible, comes in lengths of 6m or 12m, large radius bends can be formed in situ horizontally and vertically, and it reduces the number of bulkheads needed for stability on steep slopes. It is manufactured with a white internal surface to assist CCTV inspection.

At the start of trials many of the fittings were fabricated by thermal welding the pipes. A difficulty was that thermal welding of PE by hot air gun was not acceptable in the field.

Enter Plasson p/l, manufacturer of electrofusion welding kits. Heat is applied to a jacket by electric current for 80 seconds and the joint is then allowed to cool for three minutes. According to Brisbane Water there has been no record of failure of any of these joints.

According to Plasson's south east Queensland manager Mark Tibbits, the electrofusion welding process uses fittings with integral heating elements such as sockets which join pipes to pipes and saddle fittings, which are used for pipe offtakes. Other fittings include couplings, elbows and a ball socket fitting with up to 24 angle.

Pipe surfaces melt

As the electrical current passes through the wire of the heating element, the fitting and the pipe surfaces melt, generating pressure and forming a completely homogenous weld between the two. But correct handling and cleaning of pipe and fittings is essential for success.

An industry training course in electrofusion is offered by PARTEC (Plastics and Rubber Technical Education Centre) which was set up by all manufacturers of plastics to train people in the industry. It offers apprenticeships in plastic welding and authorities such as Brisbane Water demand that all its contractors are accredited.

PE pipes and electrofusion welding is used extensively in the gas industry and in mining, but it is a breakthrough for sewerage.

The third element in the NuSewers technology is the SmartStream Technology Maintenance shaft with the trade name Poo Pit, instead of manholes. A product of WA, the Poo Pit is manufactured in a softer PE, rotor moulded into a bulbous or spherical shaped tank to resist ground pressure and be strong enough for gravity sewers.

In the workshop each Poo Pit is marked with its specific location, the riser, DN250 is welded on and the required entry holes cored out and stubs heat welded in place. Then on site the pipes are welded to the stubs by electrofusion.

Wastewater saddle

Maintenance shafts are generally installed at 120m spacings, at a maximum depth of 7m.

In order to have a seamless connection from houses to the NuSewers mains, Plasson Australia in consultation with Brisbane Water, developed the wastewater saddle - a 160 or 250mm x 110mm saddle, with a 45 connection to the main pipe. The saddle can be placed at any position on the 160 or 250 main to accommodate a type A or type B connection.

With interface pressure critical to a successful joint, Plasson developed a saddle clamp to hold it in place during welding. After welding the NuSewers main is then drilled through the saddle to create the connection, then the house connection is made using Lightfit Electrofusion couplings.

All components of NuSewers are subject to vacuum testing.

MarkTibbits says that Plasson has 28 competitors in the electrofusion market worldwide, but is well supported by Australian contractors. The products are manufactured in Israel.

More information email: mtibbits@plasson.com.au.

captions

Brisbane adopts

Brisbane Water staff at a NuSewers field day

Brisbane adopts 1

Mark Tibbits

Brisbane adopts 2

A house connection

Brisbane adopts 3

A Poo Pit

Brisbane adopts 4

Saddle and strap clamp.