Sewage treatment tech that uses trees as bio-pumps

PANAJI: Sewage treatment plants (STP) largely rely on chemicals to treat waste. But if the water thus derived is rejected for reuse by citizens, as is the case in Goa, it ultimately finds its way into the sea along with the many hazardous chemicals used to treat it.

To tackle the situation, a new method of sewage treatment is gaining traction across the country; one that employs a simple method tied to reforestation, where trees act as a bio-pump. Having been featured in the second edition of the Union urban development ministry’s ‘Manual on Sewerage and Sewage Treatment’, a variant of the mechanism is presently being used in close to 70 homes, hotels and residential complexes in North Goa.

Colvale-based Joseph Lobo, a former merchant navy captain who has developed the Goa variant, patented it eight years ago as STADS, or Sewage Treatment And Dispersal System.



He began working on the concept in 2008, after he realised that he could not construct a soakpit on his farm because it lay close a river.

“STADS involves storing human waste in a collection tank and adding effective microorganisms to it, which kills the odour. The added bacteria and oxygen accelerate the breakdown of waste. The water then goes through various levels of filtration,” Lobo says. The water is ultimately supplied through a pipeline to the roots of trees planted as part of the system.

“Trees act as small bio-pumps, absorbing liquid from the soil and releasing it into the environment through transpiration,” says the urban development ministry’s manual. “It also decreases the pH of soil, bringing it to neutral levels without significantly building up salinity. Expenditure involved in adopting this technique is not much. Another positive aspect of this system is the generation of revenue through the sale of these trees from time to time for various purposes,” the manual adds.

Lobo has now petitioned state authorities to use STADS to treat waste from STPs instead of using chemicals that could contaminate groundwater and rivers. He has written to various legislators asking them to use the system to green scarred mining pits. “Waste from the different STPs in the state could be treated using this method. Growth of fruit-bearing trees along the highways could also be supported. We could then opt out of the drought-tolerant, ornamental Australian trees introduced to our environment along the highways,” Lobo explains.

STADS uses underground pipelines that can be controlled remotely using Internet of Things (IoT). The hassle of watering trees everyday is therefore, eliminated. The system is based on the fact that human waste is a major yet undervalued resource. “Each human produces 1kg of waste each day and uses 200 litres of water to flush it down. If all this is not reused, it is a massive waste. While cow dung, which is widely reused as manure, comprises only fibre and some nitrogenous compounds, human excreta is several times more fertile due to the variety of nutrients a person consumes,” says Lobo.

Benefits of the novel mechanism are evident in residential complexes like Models Millennium in Caranzalem, which comprises 314 apartments and 1,200 residents.