Scientists turn water-scarce rural school self-reliant with novel recycling method

The device that helps generate ozone to purify water at the Berambadi Primary School, Chamarajanagar district. Pic courtesy: IISc

A school struggling to conserve water in the state’s remote part found unexpected succour from scientists who developed a novel method to recycle wastewater.

With 187 students and 10 teaching staff, the Berambadi Primary School requires well over 2.4 lakh litres of fresh water annually.

Researchers from the Centre for Sustainable Technologies at IISc along with Atree, backed by funding from the James Hutton Institute in Aberdeen, Scotland, sought to recycle all this water.

“The project was driven by the fact that India commands 17.5% of the global population but has access to only 4% of the world’s total utilisable water resources,” said Lakshminarayana Rao, Assistant Professor, Centre for Sustainable Technologies, the corresponding author for the research paper published in the Journal of Water Process Engineering.

“It also stemmed from the realisation that using freshwater to clear our toilet waste, for example, is a luxury we can no longer afford,” he added.

According to experts, Berambadi was an ideal testbed because it is situated in an isolated part of Chamarajanagar district, abutting the Bandipur Forest Reserve.

Manu D, an assistant teacher at the school, told DH: “While we receive nearly 260 mm of rainfall during the monsoon, the village’s water supply becomes dire during the summer season.”

Starting from 2016, researchers began setting up a decentralised wastewater treatment system at the school. The aim was to recycle the so-called greywater which is generated by students cleaning their plates and hands after mid-day meals and wastewater generated in the school kitchen.

The researchers soon found that the turbidity (or the haziness of water) and the amount of total suspended particles is higher in India than in any other country, which means that western technologies would not necessarily be effective.

How it works

In the indigenous system, greywater from hand washes passes through strainers that filter out large food particles.

“The water then goes through three tanks with locally available coarse gravel, medium gravel and sand, where bacterial biofilms help in the breakdown of nutrients in the greywater to reduce nutrient levels,” said former Masters student P S Ganesh Subramanian, first author of the paper.

Meanwhile, kitchen greywater is passed through a grease trap to strip off the upper layers of oil and grease from the water. The water next flows through an anaerobic sludge bioreactor followed by a stratified biofiltration chamber.

Finally, the filtered water from both the hand wash sinks and the kitchen sinks is fed through an aeration tank into another tank, where ozone is used to disinfect the water and turn it clear. Only ambient air is used as input gas, instead of oxygen, to generate ozone.

“This completely eliminates the need for hazardous oxygen cylinders and makes the system relatively foolproof for local staff,” explained Professor Rao.

Manu said that the system, which was in operation for 12 months before the school closed due to the Covid-19 pandemic in March, saw 667 litres of water recycled daily. This was then fed back into the groundwater table or used to water the school garden.