VNExpress-Sept 2
A team at the Institute of Materials Science has developed a polyethylene foam to house wastewater-treating microbes, giving Vietnamese factories a domestic alternative to imported filtration media. Holding a thin white disc no bigger than a fingertip, Mai Duc Huynh of the Department of Advanced Polymer and Composite Materials at the Institute of Materials Science, part of the Vietnam Academy of Science and Technology, called it an apartment block for microorganisms.
Uniform pores inside give a single cubic meter of the material about 2,500 sq.m of surface, the equivalent of two Olympic swimming pools. Huynh registered the discs, known as porous biocarriers, under patent No. 54058 with Professor Thai Hoang, Associate Professor Nguyen Vu Giang and colleagues at the institute. Dropped into a wastewater tank by the million, the slices carry microorganisms that feed on the pollutants, a method called a moving bed biofilm reactor, or MBBR.
“There are many different wastewater treatment technologies in use, but MBBR is one of the most common solutions for domestic wastewater,” said Huynh, who traced the research to Vietnamese companies hunting for a high-quality domestic supply. The carrier filters nothing on its own but sits at the core of the technology. A low-surface-area carrier must be loaded in greater volume to house the same microbial mass, which means a bigger tank for the same treatment load. Spheres, cylinders and wheel-shaped carriers are cheap and easy to make but deliver half or less the surface area per cubic meter of the foam slices, known as biochips. Biochips digest organic waste far more efficiently and cost VND40-60 million (US$1,530-2,290) per cubic meter because they are imported, Huynh said. On the disc, the surface runs along the walls of thousands of internal pores rather than sitting only on the outer face. “The challenge in making this material is controlling the porosity,” he said. The foam needs interconnected pores yet has to survive knocking against tank walls, and it must be light enough to move through water without floating to the top.
Reaching a stable formula took roughly two years of trial and error. The team said it built the process around plastic production lines already running in Vietnam, changing only the molds and operating settings, which it expects to cut equipment spending once production scales. Nothing has been made at that scale yet, but the team estimates material costs at 25-30% of the imported product. Read more at:
