Australian city 'spreads' net to collect garbage

It has been described as the "simple pollution solution", a socklike net that fits over a stormwater drain outlet to collect trash before it enters a waterway.

For years the Australian city of Kwinana just south of Perth in Western Australia had been battling with waste such as plastic containers, bottles, paper and vegetation discharged into the city's waterways by stormwater drains.

It is a problem not unique to Kwinana, a city of 40,000 people. Cities around the world suffer from the same problem.

Last year, the Kwinana council decided to do something about it and the results were "staggering", says a spokesman for the council.

In March 2018, nets were fitted to the mouths of two local stormwater drains to trap litter and debris. Within three months 370 kilograms of trash had been collected.

The result was so good the council posted pictures of the nets on its social media page. Since then, the council has had more than 25 million hits.

"We have received inquiries from local government agencies and cities from around the world about the 'sock'," the spokesman told China Daily.

The Ecosol Net Tech (drain sock) consists of a stainless-steel sleeve extension that is fitted into existing, or new, outlets, and a removable polyethylene net, which, when full of pollutants, disengages during rainfall, effectively eliminating the risk of flooding during peak-flow storms.

Easily installed into most drainage networks the unit's simple design has a unique net release mechanism that eliminates any adverse effects when the bag fills during torrential downpours.

The drain sock is now a regular feature on stormwater drains around the city.

It is designed to catch solid pollutants such as plastic, paper and vegetation washed into stormwater drains from the road network before being discharged into the natural environment at the downstream end of the outlet area.

"Of course, the nets don't capture liquid waste but by capturing solid waste we help protect and minimize the risk to wildlife," the spokesman said.

The two nets cost the city just under A$20,000 ($13,800) which includes the cost of design, manufacture, installation and associated civil works for the two units. They represent considerable cost savings in labor-intensive work previously required to collect the garbage scattered around the reserve.

"The nets can be easily lifted and emptied into a truck with machinery. The waste is then transported to a sorting facility that processes the waste and converts the green waste into mulch and separates the recyclable and non-recyclable materials," the spokesman said.

"The Ecosol Net Tech (drain sock) has been around for some time," says Sam Kowald, business development manager for South Australian-based Urban Asset Solutions and manufacturer of the product.

He said drain sock was developed in the early 1990s by a fisherman based in New South Wales before it was acquired by the company.

"Why all the interest now? I think the idea of the net gained traction after a European environmentalist wrote about Kwinana using the nets.

"I think that aroused a lot of international interest. We have been getting inquiries from all over the world. It has really been quite phenomenal," Kowald said.

The company says the net has been sold throughout Australia and Malaysia and inquiries have been received from countries including Turkey, Brazil and South Africa.

Kowald says the drain sock is a cost-effective and efficient prescreening system for vegetated swales, wetlands and on-site detention systems.

The unit can be easily cleaned using a small crane truck for lifting the net and emptying the trash.

"During torrential downpours, the bags can fill very quickly," Kowald said.

He says the bags have a life span of around seven to 10 years.

"It is a simple device, cost-effective and easy to use. It also has an enormous impact on pollution control. It is just such a simple device."

karlwilson@chinadailyapac.com

(China Daily Global 06/14/2019 page4)