UKM News Official Portal

By Kuah Guan Oo 

BANGI, 22 July 2010 --  A reed beds system of gravels and local plants has been found to be an effective, long-term and cheaper way to treat domestic waste water .  

Devised and tested by a group of researchers from Universiti Kebangsaan Malaysia, the system is found to be a “green” alternative to the present conventional methods of treating municipal wastewater, which is a complex mixture of natural and synthetic organic chemicals. 

The group comprising Assoc. Prof Dr Siti Rozaimah Sheikh Abdullah, Assoc . Prof Dr Siti Kartom Kamarudin, Assoc. Prof Dr Fatihah Suja from the Faculty of Engineering and Built Environment and Prof Dato’ Dr Mushrifah Idris of the Faculty of Science and Technology, said unlike the present physical and chemical treatment methods, available natural plants such as wetland plants can be used to treat domestic wastewater in which the technology is known as phytoremediation. 

“Phytoremediation technology is a method to treat or remove organic and inorganic pollutants that need to be brought down to the permissible limits for disposal of wastewater.  Besides wetland construction, a reed bed system is another way of making use of the phytoremediation technology in treating domestic or industrial wastewater,” they said in their paper titled “ A Hybrid Reed Bed System for Complete Nitrification and Denitrification of Domestic Sewage.” 

The paper is published in the Directory of Research Projects (Applied and Pure Science) of the Department of Higher Education under the Ministry of Higher Education. 

For their research method, they devised a reed bed system consisting of four lines where each line had three identical beds that were made of fiberglass tanks. Gravels of different sizes were used as the media in the system with an alternative arrangement of 10-15 mm, 3-5 mm (river sand) and 30-35 mm, respectively.  The conventional method is to form multiple layers in the reed beds. 

The beds were planted with two tropical aquatic Malaysian plants – rumput kercut (lepironia articulate) and rumput menderong (scirpus grossus)  -- from Tasik Cini at different arrangements so as to allow the experiments to be carried out at different levels. Also installed was a recirculation system to enable diffusion of oxygen from the air to maintain aerobic conditions to enhance pollutants-microorganisms interaction. 

Channeling the domestic wastewater generated by more than 110 households from Bukit Putri in UKM, like toilets, bathrooms and kitchens into a sedimentation tank, they installed a pump to pump the wastewater from the intermediate level of the sedimentation tank into the designated reed beds for treatment to avoid the presence of sludge. 

What they found after five days of retention of the wastewater was significant reductions or removal percentages of the pollutants by the three reed beds as indicated by the parameters like the  Biological Oxygen Demand (BOD) of more than 99 percent, Chemical Oxygen Demand (COD) of more than 96 percent, Total Suspended Solids of more than 89 percent and pH of more than 7.

The treated wastewater met the criteria to qualify for Standard A of the Environmental Quality (Sewage) Regulations 2009, meaning that it can be safely discharged into the rivers, streams and waterways, said co-researcher Dr Siti Rozaimah.  
 
She said other foreign studies had experimented with their own native plants, so her team focused on the aquatic plants found in the country. Both the rumput kercut and menderong can be found in our wetlands, lakes, rivers and streams, growing to a height of two metres or so.  

Given the present emphasis on “green technology”,  Dr Rozaimah said their project is most suitable for small towns or settlements to treat their domestic wastewater, instead of the conventional method that involved the use of chemicals. 

In some developed societies, the people of small towns and villages take pride in their “green technology” to treat their domestic sewage,  she said, adding that an advantage of the reed beds is in its long-term operation without the necessity of emptying the beds besides requiring very little operational and maintenance input. 

Alternatively, they can use the reed beds system along with the conventional method, to cut down on the use of chemicals to treat heavy metals and other pollutants in the wastewater.  The microbes attached to the roots of these aquatic plants can degrade and absorb heavy metals and chemicals in the wastewater before it is discharged into the rivers and streams. 

She said the conventional method can remove the solid waste before the wastewater is channeled into the reed beds for treatment before discharge into the waterways.  

Dr Rozaimah said she and her co-researchers are now working on a similar “green” approach to treat the bigger challenge of industrial wastewater.  

 For this, they are looking for the best native plants to do the job. They have been scouting for plants that can still thrive in badly polluted areas, so that they can propagate them in nurseries for use in their experiments.