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Wastewater Project of the Year

For the wastewater project, commissioned during 2019, that shows the greatest innovation in terms of optimising its physical or environmental footprint. See the full shortlist showreel here.

Paso Robles WWTP, USA

What is it?

A tertiary treatment upgrade at the 18,546m³/d Paso Robles WWTP, California, including the development of a nutrient harvesting system, with treated water used for irrigation at local farms, golf courses and parks.

Who is involved?

Black & Veatch carried out project design and engineering services under a contract with the City of Paso Robles. Construction was undertaken by Cushman Contracting. Cloth filtration equipment was provided by Aqua-Aerobic Systems, and UV equipment by Trojan UV Technologies.

What makes it special?

The project massively improved the plant’s physical and environmental footprint and serves as the first step in the city’s long-term plan to create a resilient and sustainable water supply. The expanded WWTP converts wastewater into California Article 22-compliant recycled water for irrigation, a crucial move in supporting the city’s water resilience.

The nutrient harvesting system was conceived and developed during construction of the tertiary treatment facilities when it became evident that lower flow conditions had caused a struvite build-up in piping and equipment.


In addition to preventing struvite build-up, the harvesting system keeps phosphorus, nitrogen and ammonia from overloading local and state water resources. It also produces a commercial-grade fertiliser which can be sold to subsidise operating costs.

The flexibility of the design means the plant can send water to the Salinas River when demand for recycled water is low. The tertiary treatment process flows by gravity, eliminating the need for pumping and thereby saving equipment and energy expenses. Additionally, repurposed secondary sedimentation tanks that had previously sat unused allow disinfection processes to operate continuously and at a more constant rate.


Koyambedu Tertiary Treatment RO plant, India

What is it?

A 45,000m3/d reverse osmosis plant and transmission pipeline in Koyambedu, Tamil Nadu, treating wastewater for reuse at an industrial hub.

Who is involved?

The project was delivered under an $83 million, 15-year design-build-operate contract signed between the Chennai Metropolitan Water Supply and Sewerage Board and a consortium comprising VA Tech Wabag (80%) and IDE Technologies (20%), supported under the Indian government’s AMRUT programme. Equipment for the plant was supplied by Inge (low-pressure membranes), Dow and Pentair (RO membranes), Wabag Austria (valves), Bharat Minerals/Kalimati Carbon (sand filters) and Xylem (ozonation units), among others.

What makes it special?

The plant is the largest and most technologically advanced reuse project in India. It is the first reuse facility in India to use ozonation for disinfection and marks a decisive step for the country’s ambitions for municipal water recycling. Furthermore, with the completion of the TTRO, Chennai is now the first Indian city to reuse more than 20% of its treated wastewater.

The project will boost Chennai’s water resilience and sustainability in the wake of the city’s ongoing struggles with drought and water scarcity.


The TTRO will help free up over 16 million m3 of freshwater each year, securing water supply for Chennai’s population of more than 10 million people.

The TTRO uses a multi-stage treatment scheme, including ultrafiltration, reverse osmosis, rapid gravity sand filters, and ozonation. The UF and RO membranes achieve a recovery rate of 75%, and the plant has an ultra-low specific power requirement of 1.88kWh/m3, which is expected to incur significant savings in the plant’s operating costs over the next 15 years.