New standard for hospital wastewater treatment

Small amounts of hormone-disrupting substances and other medicine residues are also part of the mix that passes from patients through hospital toilets and into public sewer systems. But now a full scale plant in Denmark has removed these residues, potentially addressing a worldwide problem.

The BioBooster system purifies hospital wastewater in three steps.

The issue of hospital wastewater being sent to public sewage treatment facilities is a major problem according to Ulf Nielsen chief environmental planner with the water environment consulting firm DHI Denmark.

“Municipal sewage treatment plants are not designed to deal with medicinal and biological waste. This is why we can now detect these substances in our waterways,” he said. Mr Nielsen points out that hospital wastewater can pose a health hazard to humans, especially employees at wastewater treatment plants. During heavy rains and flooding, holding tanks in the sewer system can overflow and expose the public to these hazards.

There is also a danger to marine life. Once the sewage is treated and released into the environment along with its residual content of pathogens and pharmaceuticals, the local fauna are routinely at risk.

“Even in very low concentrations, the substances in hospital wastewater can affect animal life,” Mr Nielsen added. “Estrogens, for example, can cause hermaphroditic fish, while some painkillers are poisonous to trout and certain psychopharmaceuticals can affect fish and bird behaviour.”

The Municipalities in Denmark has now taken steps to start regulating the largest hospitals in Denmark using the experiences from the plant at Herlev Hospital., according to Poul Madsen, group vice president of Grundfos’ Global Water Treatment Solutions. “Regulations will begin to come into effect within a year or two, but right now there are still no requirements for special treatment processes. Hospital wastewater and household wastewater are treated in the same way – and that’s not a very effective approach.”

Part of the Grundfos Biobooster treatment process involves sending the hospital effluent at very high pressures through a series of membrane filtration units.

Watch list

Meanwhile, the European Commission has placed three pharmaceutical products on a ‘watch list’ of substances that may be regulated in future. Right now, however, there are no European standards for pharmaceuticals or pathogens in hospital wastewater.

To deal with the wastewater issue, the regional government of Greater Copenhagen (the Capital Region of Denmark), established an innovation partnership in July 2012 that involved Herlev Hospital and a number of other public and private players, including DHI Denmark and Grundfos.

The goal of this partnership was to find a solution that actually removed the problematic substances in hospital wastewater rather than simply diluting it with other wastewater streams in the public treatment system.

“Grundfos had previously tested some really good technologies on a laboratory scale together with a couple of other hospitals in our region. Bringing Grundfos into our partnership allowed us to build on this experience,” said regional chairman Sophie Hæstorp Andersen.

The result was a compact, tailor-made wastewater treatment plant designed by the Grundfos BioBooster business unit and set up next to the hospital. Local treatment of wastewater is key to the success of the system, according to Grundfos’ Poul Madsen.

“Our plant receives wastewater directly from the hospital. It is not mixed with the water from the public wastewater treatment system. This makes it possible for us to specifically target the substances in hospital wastewater,” he said.

The new treatment plant involves biological purification, filtration using ceramic membranes and a final “polishing” with activated carbon and ozone. This modular system is extremely flexible. Each element can be expanded, removed or adjusted to accommodate changing needs. The physical layout of the plant is also fundamentally different from traditional wastewater facilities.

“Wastewater from hospitals is typically fed into large, municipal treatment plants that take up a lot of space and require long pipelines from the hospital to the treatment plant,” Mr Madsen said. “We have developed a compact water treatment plant that can be delivered in four or five pre-fabricated modules. It’s no bigger than a small house and it enables hospital wastewater to be treated locally and then safely released into the local environment.”

Christine Anna Hastrup, environmental engineer at DHI, samples of treated wastewater from Herlev Hospital near Copenhagen, Denmark.

Airborne pathogens

Odours and any airborne pathogens are also locally treated. They are cleansed from the air before it is released from the closed treatment system. Sludge from the system (including any remaining pathogens) is dried on site and then transported off-site for incineration at a local incineration plant. All in order to develop and demonstrate a complete solution for point of source treatment of hospital wastewater.

DHI will continue to conduct tests on the plant until end 2015 in order to document treatment efficiencies, operational cost and to find the optimal combination of ozone and granular activated carbon. During this phase, the treated water will be piped into the public sewage and wastewater treatment system.

If the test results from DHI live up to the promise that has been shown so far, the purified water will eventually bypass the public systems entirely. Instead, part of it will be re-used locally as technical water at the hospital – and some will be released directly into the nearby Kags River, where it will contribute to a more stable water flow during the summer months. In other words, the water that was once a risk can in future become a resource.

Mr Madsen is pleased the authorities are taking a greater interest in the subject of hospital wastewater regulation. In Denmark, the treatment plant at Herlev will help set the standard for the coming municipal regulation of hospital wastewater, he says.

“There is a great need for regulation in this area. We are releasing all sorts of substances into the water that our descendants will have to drink,” he said.

He also believes that formal threshold limits on the medicinal and biological substances in wastewater will boost the interest in proven technologies that can enable hospitals to live up to the new requirements.

Ms Andersen is convinced the newly-inaugurated treatment system could have great significance for hospitals around the world that face the same problems as Herlev Hospital.

“We believe we have the solution to a problem that exists at a great many hospitals, both in Denmark and in other countries. It has already stimulated international interest and we have had visits from a number of international delegations, including one from China.”

Mr Madsen also has high hopes for the future of the new wastewater system. “Herlev Hospital is the first hospital in the world to install this technology. But I believe it has far greater potential. In the years to come, I think this technology will become extremely important – especially in industrialised nations where there is a political interest and a focus on the environment.”