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Figure 1: Liquefied Biogas from Food and Sewage Used for Running Public Buses in City of Oslo, Norway

Currently, only approximately 30-35% of the Indian population is connected to the sewage network, requiring large infrastructure projects for treating wastewater.

By Dr. Ashish K Sahu

By 2030, the United Nations predicts the world shall have 43 megacities, each with a population greater than 10 million. Population growth and urbanization turn towns into large cities and large cities into mega cities. About 90% of this shift will take place in Asia (India, China) and Africa, pressing municipal utilities to upgrade their infrastructure, either by building new or upgrading their systems and plants. Out of the 43 megacities, Mumbai and Delhi are ranked to be in the Top 101.

Many western stakeholders see India as an emerging market in the wastewater sector, where the demand for greenfield projects are growing. Currently, only approximately 30-35% of the Indian population is connected to the sewage network, requiring large infrastructure projects for treating wastewater.

Even as India focuses on wastewater, the world is moving towards a circular economy, with ambitious targets for resource recovery. The World Economic Forum shows many ways in which cities can become more sustainable, by designing their infrastructure and system for a circular economy. In the past, when most people dwelled in smaller villages and towns, food consumed by humans turned into waste was recycled back to nature (organic waste), thus closing the loop. With urbanization came demands for landfill and incineration, breaking the loop cycle back to Mother Nature. The question for Indian cities is how they can cope with tremendous growth at an affordable cost while becoming more sustainable and facilitating the recovery of valuable resources from increasing waste streams.

There are many challenges wastewater utilities need to tackle and manage to achieve a sustainable solution: meeting changing and increasingly stricter regulations, reducing the carbon footprint, working with the current space availability in large cities, holding investment costs within available capital resources, reducing operational costs to keep fees affordable for households.

Balancing the risks and selecting the right proven technologies is without a doubt very complicated process. All investments decisions require thorough evaluation, due to the high cost, complexity and long lifetime of large infrastructure projects (20-30 years). Several stakeholders from academicians and technology providers to consultants and contractors thrive on giving out information addressing these challenges.

One key aspect to keep in mind when talking to the water utilities about the trade-offs of their choices is the generational gap. The “old school” dominates decisions in a conservative public sector, perceiving the younger generation as inexperienced. However, many seasoned decision makers may be unaware of the technological advancements during the last decade(s), hence being reluctant to accept or leapfrog to new advanced solutions. Overlooking new technologies bears the risk of getting stuck with outdated, expensive solutions for decades to come, at great cost to society.

In the western world (Americas, Europe) a lot of funding is channelled into the research and development of environmental process technologies. The IT sector stands out when it comes to the commercialization of new solutions (think of the switch from landlines to smartphones), and the ripple effects are now reaching the core of environmental sectors, bringing substance to the much touted 4th industrial revolution. Already, a few companies are bringing to market disruptive technologies that are taking wastewater utilities by storm, offering novel ways to address the complex food-energy-water nexus.

Cambi is one such Norwegian company in the sludge management business who have brought out disruptive technology in the wastewater sector. Over 25 years, Cambi has built a market and is a proven supplier of thermal hydrolysis (CambiTHP®) for sustainable sewage sludge. You may wonder: Why focus on sewage sludge?

In a wastewater treatment plant, conventional technologies include primary treatment followed by biological treatment and nutrient removal/recovery. The wastewater is clean when discharged in line with the regulatory requirements however, most of the pathogens are transferred in the resulting sludge. Sludge management is an essential, complementary aspect of wastewater operations which in many emerging markets tends to be ignored or treated as a minor issue.

Unfortunately, many cities leave the sludge from wastewater operations untreated or settle for composting or liming. These are relatively inexpensive ways for towns to achieve sludge stabilization before sending low-pathogen sludge back to nature. However, this is not the ideal solution for cities, where large volumes of sludge are costly to store, haul and/or landfill, with the added issue of leaching. Conventional alternatives for sludge management in cities are drying, pyrolysis and incineration, but these are energy intensive and prohibitively expensive.

The most sustainable way to treat sludge is to produce bio-energy (biogas). In ancient times in India, cow manure was used to produce biogas using the “GobarGas” (anaerobic digestion) technology. The wastewater utilities of large cities can use similar, but more advanced technology for sewage from human waste. There are many uses for clean gas in a large city, such as running buses/transport in cities (Figure 1) and/or producing electricity. Many full-scale, commercial installations stand proof of the potential. For example, at the Basingstoke wastewater treatment plant (near London, UK), the biogas from local and imported sewage sludge is used to produce electricity for the treatment plant’s own consumption. The wastewater treatment plant with sludge treatment even becomes a net exporter of energy rather than an importer.As a side benefit, sludge cake with the right set of technologies in sludge management can be used for direct agricultural applications.

Figure 2: Sludge Management for Mega Cities Using the Cambi Proposed Sludge Line

When thinking of sustainable sludge treatment, there are several unit operations to consider in the process train: Dewatering, Thermal Hydrolysis Process (THP), Anaerobic Digestion, Combined Heat, Power and Land Application (Figure 2).

Figure 3: Key Benefits of Using CambiTHP™ Technology for Sludge Management

Among the key benefits of such a unit process train is the production of a pathogen-free and odor-free cake that can be easily be applied in agriculture as nutrient-rich, organic fertilizer. Applying the CambiTHP® process results in higher biogas production and smaller anaerobic digesters with higher capacity. In addition, upon final dewatering, the result is a smaller quantity of cake, meaning less transportation needed for disposal (Figure 3). In other words, thermal hydrolysis acts like a catalyst in the sludge management solution.

In many cases, the water utility achieves a lower lifecycle cost for their operations while becoming more sustainable, due to lower infrastructure requirements, higher renewable energy production, lower carbon footprint, and lower transportation costs.

For technology selection, the best advice utilities in India can get is, “Seeing is Believing”. Since the capital investments are high for such projects, it is important to consider the entire lifecycle costs and study similar case studies from leading utilities in the world. CambiTHP® is a proven technology with 65 installations in over 22 countries worldwide, serving many megacities such as Washington DC, Singapore, London, Beijing, to name a few.

Wastewater utilities in India have now the opportunity to leapfrog the old-fashioned, conventional technologies of the 20th century and think of accepting proven technologies for the 21st, looking at the entire lifecycle costs to become modern sustainable cities. The IT sector has leapfrogged and the time has come for the environmental sector to do the same. As India is becoming a strong economic power, the land is becoming expensive, labor is increasingly costly and fuel is weighing heavy on utilities’ balance sheets. Storing or hauling the sludge in cities like Mumbai and Delhi will not be a sustainable option. This will lead to a shift in how technology is accepted and applied. However, even though it is easy to upgrade to a new telephone quickly today, such is not possible in capital intensive infrastructure projects like a wastewater treatment plant. As pointed out earlier in the article, choosing the right solutions is a balancing act for utilities. The right strategy is to think long-term, selecting the solutions that help convert waste to worth.

About the Author
Dr. Ashish K Sahu (Ph.D., MBA) is currently working as Marketing Manager in Norway based Cambi Group AS.

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