Salvaging sewage

Published On: June 10, 2016 02:07 PM NPT By: Sneha Pandey

A couple of years ago, a college trip took my classmates and I to the Gujeshwori Wastewater Treatment Plant in Kathmandu.

On my part, it was a well-anticipated trip as I had many questions about why the river systems of Kathmandu were so polluted and what was being done to stymie the unrelenting flow of dirty water into the Bagmati.

In retrospect, I was convinced that all the sewage channels to the rivers must be completely blocked and all the waste water redirected. Where? I had no idea. But I was convinced that there had to be a sustainable solution.

During the trip it was clear that – as with many other projects that do not show immediate and significant profit margins – there was a definite lack of interest from the government’s part in this arena. For one, we were informed that in spite of the presence of five different municipal treatment plants in Kathmandu, the Gujeshwori plant was the only one that was in operation. Secondly, given all the power cuts and other maintenance issues this plant was operating at less than three-fourths of its actual capacity.

This should have been unacceptable given the vital role that such plants play – in major cities around the world – for the maintenance of human sanitation and preservation of river ecosystems. In Nepal, however, it is a norm to shrug off such environmental and sanitary concerns. As citizens of a country with a struggling economy, few understand the benefits of adopting a long term vision and investing in the construction, operation and maintenance of effective sewage systems.

Given, the right conditions, wastewater treatment can be made both profitable and environmentally conscious at the same time; take the treatment plant in Gujeshwori for an example. The plant collects waste water from the Tilganga area. It removes solid and inert materials using mechanical screens and grit chambers and organic wastes by using settling tanks and by deploying bacteria to digest them. Eventually the plant releases water – that has been estimated to be 60% cleaner – back into the river system.

This water that enters the river is deemed to be able to support various aquatic life forms, which means that if such a cleaning system is deployed throughout the valley then reintroduction of fishes into the rivers can be a real option in the near future. On the other hand, the plant also generates some income by collecting the sludge from the settling tank, sun-drying it and selling it to farmers as fertilizers.

Another bigger possibility in the future of waste water treatment is using microalgae instead of bacteria in open ponds to produce end products such as fertilizers, food and even – the much more lucrative – biofuels. Biofuels are all the rage in the scientific communities right now as scientists try to figure out how to produce these fuels that are able to compete with the energy content, longevity, stability and economics of fossil fuels in the international arena.

As the world’s store of the fossil fuel depletes and with increasing concentrations of GHG released by burning them, the search for a greener and sustainable alternative has become largely concentrated on these microscopic saviors – microalgae. The oil content of these photosynthetic, single celled plants is so insanely high that its capacity for biodiesel production has been considered to be almost a thousand times higher that of land crops like canola, soybeans, jathropa and palm oil.

This is good news all around. Using microalgae instead of crops for biofuel production means that competition with food crops for land, fertilizers and water decreases which will subsequently prevent increase in food prices in the future. The byproducts that can be extracted during algal biofuel production like food, supplements and fertilizers can also be sold for profit. Since microalgae are fast growing, genetically diverse, easily amenable and can use pretty much anything – including our waste water – for nutrients, they have become a huge commodity in the scientific world today.

Scientists, in the West, have up till now grown algae in open ponds, in tall glass fermenters and are even experimenting with offshore plastic fermenters that float just under the waves of the ocean. So what does this mean for Nepal? While it would be unrealistic to assume that we could afford to build and maintain huge biofermenters to process wastewater and convert it to biodiesel, open algae ponds are a very real possibility here.

Since algae require carbon dioxide for photosynthesis – that would otherwise be released into the environment as a potent greenhouse gas – CO2 produced from other sources can also be sequestered along with treatment of waste water and production of environmentally friendly, high value products.

Today, the Bagmati Basin is facing serious environmental and ecological challenges. While the water to the upstream of urban areas are considered to be relatively cleaner, upon entering cities water become severely polluted with untreated wastes. This has virtually erased all aquatic lifeforms in the river. Such rampant activities of municipalities and industries have also severely hampered the aesthetic value of a river that is very strongly embedded in our culture and religion.

In spite of such activities, few solutions have been sought up to date in Kathmandu with the exception of the Gujeshwori Plant whose benefits are isolated to a small area around the Tilganga region. This is clearly far from enough. In the future, it is necessary not just to build waste water system in a dispassionate manner (so that they are abandoned later when costs cannot be met) but to build them in such a way so that two birds – reaping profits and saving the world around us – can be killed with the same, well-aimed, stone.

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