New Research On Crushed Glass As A Wastewater Filter

2A concrete sand is the most commonly used sand filter in New Zealand’s wastewater treatment systems, but it’s expensive, and not always available - so what about crushed glass?

Through his research with TM Consultants, final year Civil Engineering student Quang Truong tested crushed glass as a substitute filter for wastewater discharge trenches, and found it to be a more economical and sustainable alternative for rural areas.

"Our final year projects are basically about working with industry to find innovative ways to solve a problem. We have a huge stockage of recycled glass in our country and we need to find a viable market to reduce that as much as possible," says Truong.

The research found that using crushed glass as filter media for a typical 3-bedroom house could save up

to $500 and reduce 200kg of carbon dioxide released to the environment during the manufacture, transport, and construction phase.

"The exciting results of these findings provide New Zealand based, real-world data that can be used by TM Consultants as an expert in onsite wastewater treatment system design, and local territorial authorities, in the consenting processes," says Marc Jensen, Senior Hydraulics and Mechanical Engineer at TM Consultants.

Truong has been working with TM Consultants and Ara Project Supervisor Matt Ramezanian Pour to write an academic journal article to be published in early 2022 which is also intended to be provided to Environment Canterbury (ECan) to float the idea of this new filter medium.

"Sustainability is a major part of this project, and this work demonstrates a valuable collaboration between industry and academia," says tutor, Matt Ramezanian Pour.

After six months of testing, results showed that crushed glass matched the performance of 2A sand for Total Nitrates (TN), Biochemical Oxygen Demand (BOD5) and Total Suspended Solids (TSS).

"In New Zealand, we have never done anything like that before. I was actually invited by ECan and WaterNZ to deliver a presentation of the findings with TM Consultants. So it’s great if we can get this work published, then we can refer it to ECan and hopefully actually use it. It would save a lot of money," says Truong.

Every year Ara holds an Engineering Showcase, to display and award the work of students from the Bachelor of Engineering Technology.

This year Truong’s won him Best Project - Civil Engineering and Industry Choice - which means out of all the industry present on the night Truong’s project was the top pick.

"I consider it the most prestigious award," says Rob Dantzer, Manager- Department of Engineering and Architectural Studies.

"A really neat thing about Quang’s project is an industry client came to us with a problem, he tested mediums and produced tangible results. Now TM Consultants are looking at getting permission from Environment Canterbury to use crushed glass as a filtration medium," Dantzer adds.

Truong came to New Zealand from Vietnam three years ago, and enrolled in Ara as an international student. Before he could enter the Bachelor’s Degree, he needed to fill a few gaps in academic requirements; something which he took in his stride.

"He’s a young man who has said yes to opportunity, and ultimately hard work and persistence have paid off," says Dantzer.

While completing his degree Truong is working part-time for Cosgroves in their civil engineering team, working across land development, roading and three waters projects.

Truong says, "I would like to progress in the land development industry. My favourite thing about engineering is problem solving, and working on things that can bring value to humankind. Now I'm working on a few projects and sometimes I go out and I see it actually being built and it's just so rewarding!"

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