Why is wastewater reuse difficult at source?
The high cost and high-energy requirements of providing a reliable supply of clean water, especially in the Gulf, necessitate the exploration of more viable, environment friendly and economically sustainable options.
In residential buildings and commercial properties, non-potable water applications such as toilet flushing, cleaning, cooling towers and landscaping constitute as much as 95% percent of the total water consumption. The resulting wastewater is discharged into the sewer systems. In un-sewered areas, they are mostly discharged into open areas untreated or semi-treated. Wastewater reuse rarely happens at source. As the energy, financial and environmental costs embedded in potable water are high; using high-quality potable water for non-potable purposes is not an efficient way of using a scarce and vital resource.
How can it be done?
Some building owners have tried ways to reduce consumption of high-quality potable water for non-potable applications in buildings. However, existing measures, in particular rainwater harvesting and greywater recycling have not proven to be adequate and cost effective. Rainwater harvested is almost certainly insufficient to offset the non-potable water consumption within buildings due to the issues of intermittency and limited storage space. Greywater (from washbasins, showers and laundry) recycling on the other hand, requires dual plumbing to separate greywater from other forms of wastewater. Such separation is not available in most buildings and retrofitting is costly.
Given the above limitations with the current solutions, there is a need for an on-site wastewater recycling solution that can generate a more predictable and significant source (in terms of volume) of non-potable water on-site. The solutions also need to eliminate or reduce the need for major retrofitting in existing properties without dual plumbing or dedicated pipe systems and be adaptable enough to meet the requirements of different properties. The solution should also be scalable and modular enough so that the system can be scaled-up or down to meet a property’s changing water consumption patterns.
By providing an additional source of fit-for-purpose water, buildings can use every drop of water more than once, taking in less piped water and reducing wastewater discharge into the sewer network. This complements the centralized grid by reducing the load on grid and reducing the cost of water, especially when the supply of water through desalination comes at a high cost.
What is a Water Smart Blue Building?
The Water Smart Blue Building is a technology platform pioneered by ECOSOFTT through the decentralized and integrated management of water. It allows buildings to become water sustainable by recovering and reusing wastewater using low energy and high water recovery technologies to enable “Point of Use Reuse”; better optimizing water from different sources, such as rain and ground water and using non-potable water for non-potable purposes. It also allows the deployment of smart accessories to monitor and manage water usage that can be integrated with Building Management Systems and Data Analytics.
What criteria needs to be considered to achieve this?
Implementing decentralised water management systems present technical requirements and challenges that are somewhat different from municipal treatment plants. Several important criteria needs to be considered to maximise user benefits and environmental impact including high treatment efficiency with the ability to manage fluctuations in wastewater contamination level from time to time and a small footprint to minimise real estate cost. Other criteria to consider include reliable performance and easy to operate as there may be no technical specialist on site; and no or minimal sludge from process, which would otherwise be cumbersome to dispose. Also relevant are the criteria of no odour to avoid negative impact on building users; low energy consumption and operating costs and minimal use of chemicals for environmental sustainability.
What is a good example of a Water Smart Blue Building?
A successful example of the deployment is JTC CleanTech One, an eco-building in Singapore with 37,000 square metres of space. The on-site wastewater treatment system eliminates the need for extensive retrofitting, dual plumbing, dedicated piping systems required for conventional greywater recycling. A Water Smart remote monitoring and control system enables the entire system to be monitored and controlled remotely on a real-time basis, thus reducing on-site manpower for operations and maintenance.
The entire system was designed to blend into the built environment with no impact on the building structure and the aesthetics of the existing building. A good part of the original greenery is preserved. An architectural wall was built using sustainable materials and a Green Wall, which can be irrigated using recycled water was added to the entrance of the setup.
The end result gives the effect of a “Wastewater Recycling System in a Garden”. This effectively dispels the common perception that wastewater treatment systems are dirty and unsightly, and have to be placed in faraway or hidden areas.
This project has proven that recycling and reuse of wastewater at a building level can be technically feasible, socially acceptable and financially viable. The possibility of customizing water to any required quality further challenges the conventional wisdom of using potable water for non-potable purposes, which account for almost all the water used in industrial estates.
What are the next steps?
Depending on the water sources, tariffs structure and local costs, recycling may be viable at different scales. In many cases, managing recycling at an estate level could provide more flexibility in storage options and excess water from one building can be sent for use in another building that consumes more water. In such a framework, the end users become active partners and collaborators with service providers and utilities in the management of water from source to source, at source.
By Marcus Lim, Co-Founder & Managing Director of ECOSOFTT