Many cities in the world are grappling with water scarcity due to lack of clean water resources and their constant degradation. From flushing the toilet to taking a shower to working in the kitchen, excess water and everything that comes with it travels down the drains and ultimately to wastewater treatment facilities. The amount of wastewater, sewage sludge and biowaste is increasing due to rapid urbanization and growing population, which represents a risk to the environment and human health. To address the growing risk of water, water processing utilities are seeking advanced, sustainable, and cost-effective solutions to harvest as many resources as possible from waste. Sewage sludge can become a valuable source of nutrients, known as biosolids, once treated. Biosolids have a variety of applications such as fertilizers on agricultural land due to its soil conditioning properties.

The conversion of sewage sludge into biogas and advanced liquid biofuels has significant potential to contribute to the world’s renewable energy and circular economy. Thermal hydrolysis is an innovative wastewater solids conditioning process, applied in wastewater treatment plants with anaerobic digestion. It involves exposing sewage sludge or other types of wet organic waste to high temperature and pressure to break the cellular tissues down to their original smaller molecular components. The thermal hydrolysis process (THP) increases the biodegradability of wastewater residuals, reduces viscosity, destroys all infectious agents, boosts digester loading rates, and increases biogas production. Hence, many wastewater management facilities are now increasingly investing in thermal hydrolysis technologies to reduce their disposal costs and improve dewaterability. The main functions of thermal hydrolysis technology involve waste side product minimization, biogas generation, and wastewater treatment.

Thermal hydrolysis is a two-step process that combines pressure cooking and rapid decompression. Together, these processes weaken the lignocellulosic material's chemical bonds, enhancing biodegradability and supplying a larger surface area for anaerobic digestion or fermentation organisms to work on (therefore allowing higher loading rates, or shorter retention times). The high temperatures used also sanitise the feedstock in the case of manures and sewage sludges, eradicating any potential pathogens and expanding the digestate's uses, such as its usage as a premium biofertilizer. While conventional digestion requires thickening prior to the process, thermal hydrolysis requires upstream dewatering.

Use of thermal hydrolysis can yield up to 50% more biogas than conventional digestion process. Moreover, utilities can save a lot on the construction of anaerobic digesters by optimizing digester throughput leveraging thermal hydrolysis technology. The final biosolids obtained from thermal hydrolysis are odour-free, pathogen-free, and can be utilized as organic fertilizers.

Recently, San-Francisco Public Utilities Commission (SFPUC) has selected Cambi thermal hydrolysis technology for new biosolids digester facilities for wastewater treatment by investing over USD3 billion. The investment has been made to upgrade and modernize the Southeast Treatment Plant

New Low-Temperature Thermal Hydrolysis Biosolids Technology

Canadian company specializing in thermal hydrolysis solutions for biosolids and organics, Lystek International, has developed new range of practical solutions for biosolids and organics management. The new range of Lystek Mobile THP provides a practical solution to the growing market demand for smaller scale treatment plant operators for sustainable biosolids management solutions in support of the movement towards resource recovery. Lystek Mobile unit is the smallest commercial system built to operate entirely within two vertically stacked 50’ containers and requires minimal external utilities. Besides, the mobile THP provides operational flexibility for generators of biosolids, produce federally recognized Class A quality biofertilizer product, and optimize the value of digester infrastructure. Moreover, Lystek Mobile THP creates a cost-effective and alternative source of carbon for Biological Nutrient Removal Systems.

Since capital remains a key constraint for small to medium sized wastewater treatment plants, Lystek Mobile THP offers a practical solution to respond to the evolving regulations surrounding biosolids management. The new Lystek THP can be matched to the processing needs and leased for short term to meet the market demands and address challenges requiring time-sensitive solutions.

Cambi Collabs with Veolia to Acquire Complementary THP technologies

In May 2022, Cambi signed an agreement with Veolia Water Technologies to acquire Veolia’s thermal hydrolysis process (THP) technologies, registered under trademarks Exelys and Bio Thelys. The acquired technologies will enable Cambi’s entry into potentially large market segments such as CAPEX sensitive wastewater treatment plants and biogas substrates other than wastewater solids and food waste. The collaboration will open new opportunities to strengthen Cambi’s position as the world-leading supplier of treatment solutions for wastewater solids and organic wastes in anaerobic digestion projects.

Bio Thelys is a complete sludge reduction solution that combines thermal hydrolysis and anaerobic digestion. Exelys is another complete sludge reduction solution that works in continuous mode with real time adjustable feed rate. Exelys operates under controlled temperature, pressure, and residence time conditions.

Piscataway Bioenergy Project

WSSC Water has decided to install one of the first thermal hydrolysis process units to transform the ways to handle waste from five existing water resource recovery facilities. The Piscataway Bioenergy Project is the largest and most technically first-of-its-kind ever constructed by WSSC Water that would utilize innovative technologies to produce green energy. The project to be executed with an investment of around USD271 million is expected to serve customers for the next 100 years as the plant will evolve into a bioenergy production facility that uses efficiency, technology, and sustainability. Using cutting-edge technology, the new bioenergy facility will reduce the amount of biosolids left from the treatment process, allowing the final product to be sold and distributed as fertilizers. The progressive design-build project delivery method will open new ways to economize and improvise when needed before locking in a final price.

Way Ahead

The development and advancement of such technologies will pave a way towards a sustainable future, taking into account the amount of biowaste generated. The treatment of biowaste has led to development of new value chains and industrial opportunities. Huge investments by wastewater management facilities and push by the government to adopt new technologies are some of the factors expected to drive the adoption of thermal hydrolysis process technology.