Water - can less be more?

Rip Copithorn* discusses a range of technologies that will influence the future of wastewater treatment and change the way we think about water security.

A need to do more with less is a constant theme in most industries and utilities these days and the wastewater treatment industry is no exception.The general goal of sustainable wastewater treatment includes a number of efforts that range from improving instrumentation and control systems to reduce chemical and energy demands, implementing treatment processes that are more efficient and incorporating resource recovery processes that recover treated water, phosphorus, nitrogen and power from the waste stream. A leading trend illustrates that wastewater treatment is rebranding itself as a resource recovery industry.

Innovative technologies and processes are being developed that show much promise in achieving these goals of sustainability. For facilities that must meet low level nutrient permits, novel processes using anammox (ANaerobic AMMonia OXidation) bacteria to eliminate nitrogen with much less demand for energy and chemical are showing promise. Anammox  is a process that avoids having to oxidise ammonia all the way to nitrate (as in conventional biological nutrient removal), thus greatly reducing the amount of power required for aeration. Anammox does not require supplemental carbon for denitrification, thereby eliminating the cost of methanol addition. The process has been commercialised and is well proven as a sidestream treatment process to reduce the amount of ammonia being returned to main stream treatment by the sludge treatment process. Research is currently underway to adopt anammox to mainstream treatment.

On the resource recovery front, there are several processes available to recover and pelletise phosphorus from wastewater for use as a fertiliser. This is increasingly important as the world’s sources of virgin phosphorus ore are limited. This technology is also proven and has been commercialised.

Water, of course, is also a renewable resource and advanced treatment processes to treat wastewater to increasingly more stringent levels for re-use are available. The main impediment to re-use is not technology, but rather continues to be economics, regulatory issues and public perception. But the demand for water in certain areas of the world continues to encourage re-use. The ‘water/energy nexus’ is getting increased attention as it is recognised that power generation requires water and water production requires power. Now, innovative projects to recycle water from wastewater treatment plants collocated with power plants and to re-use heat and power from the wastewater treatment plants in a sustainable cycle are appearing.

Some utilities have established the goal to have ‘net zero’ energy demand and even put energy back into the grid through improving treatment efficiency and the production of electricity from biogas. There are advances in improving biogas production from waste sludge through predigestion processes that break down the biomass in waste sludge, making the organics more available for the generation of biogas. There are numerous technologies to produce energy from biosolids including pellitisation, gasification, slurrycarb, biodiesel production, hydrogen gas formation and pyrolysis. Technologies are available to use waste sludge as a fuel in the form of a solid, liquid or gas. Wastewater can be used to grow algae, which then becomes a feed stock to produce biodiesel fuels.

Technical advances provide much reason for optimism but in some ways we are our own worst enemy. The wastewater industry is typically very conservative and reluctant to embrace new technologies.This is understandable given the regulatory pressures and penalties for non-compliance. Large plants facing expensive upgrades can justify pilot projects to demonstrate developing technologies, but even then regulatory agencies, funding sources and utility owners can be reluctant to take the risk of incorporating innovative processes without an extensive track record. 

Fortunately, there are organisations that recognise these impediments and are seeking to encourage innovation through collaboration between researchers, academic institutions, utilities and the engineering community. Organisations such as WEF, WERF, WaterRF, AWRCOE and others share the cost, the risk and the results of projects to demonstrate and improve technologies. Hopefully this will accelerate the industry search for proven sustainable treatment alternatives. With this backing, wastewater treatment facilities in the future will look very different than the conventional treatment plants of today.

*Rip Copithorn is GHD's Global Technical Leader - Water. He has more than 37 years’ experience in water and wastewater engineering. This includes research and development, water pollution control equipment performance and evaluations, site planning, facilities planning, and preliminary and final design of water and wastewater facilities, construction management and computer modelling for process design. He has also presented a number of seminars and papers regarding the upgrade of wastewater treatment facilities for nutrient removal.