Water Treatment for Hospitals

New Treatment Plant Involves Biological Purification Processes as Well as a System of Ceramic Filtration Membranes and a Final "Polishing" with Activated Carbon and Ozone"

Wastewater from hospitals around the world can generally contain traces of anything from viruses and multi-resistant bacteria to medical contrast agents and chemicals for cancer 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.

From there it is generally sent to a public sewage treatment facility. This is where the problem really begins, according to chief environmental planner Ulf Nielsen of 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," says Ulf Nielsen, who has studied the problem of hospital wastewater for a number of years.

Wastewater is hazardous to health and the environment

Ulf 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.

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," Ulf Nielsen says. "Estrogens, for example, can cause hermaphroditic fish, while some painkillers are poisonous to trout, and certain psychopharmaceuticals can affect fish and bird behaviour."

Regulations for hospitals are still not fully implemented

Municipalities in Denmark are still working on the problem of how to regulate and standardise the treatment of hospital wastewater, says group vice president Poul Madsen of Grundfos' Global Water Treatment Solutions: "Regulations will begin to go 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."

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.

An innovative partnership sets out to solve the problem

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 involves Herlev Hospital and a number of other public and private players, including DHI Denmark and Grundfos A/S.

The goal of this partnership was to find a solution that actually removes the problematic substances in hospital wastewater rather than simply diluting it with other wastewater streams in the public treatment system. Asking Grundfos to become part of the partnership was a natural choice, says regional chairman Sophie Hæstorp Andersen.

"Grundfos had previously tested some really good technologies on a laboratory scale together with a couple of other hospitals in our region," she notes. "Bringing Grundfos into our partnership allowed us to build on this experience."

Decentralised treatment is the key to success

The result of this innovation effort was unveiled on 2 October 2014: a compact, tailor-made wastewater treatment plant designed by the Grundfos BioBooster business unit and set up right next to the hospital. Local treatment of wastewater is key to the success of the system, says 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 explains.

Safe, flexible - and fundamentally different

The new treatment plant involves biological purification processes as well as a system of ceramic filtration membranes and a final "polishing" with activated carbon and ozone. The system is extremely flexible: each element in this modular system 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," Poul Madsen says. "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."

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.

Treated wastewater can become a resource

The treatment system is still only a pilot project. Until the pilot phase ends in mid-2015, DHI will continue to monitor and test the treated wastewater for the presence of some 100 different substances. 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 part of it 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 the future become a resource.

Source: The Guardian

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• Water Treatment & Control
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