Hospital wastewater often contains a complex mixture of pharmaceuticals, resistant bacteria, contrast media, and other problematic substances. Municipal wastewater treatment plants are not designed to treat hospital wastewater, and as a consequence, these substances find their way into the aquatic environment. Several studies have confirmed the harmful effects of many of these substances, and the result is damage to aquatic life and health risks to sewage workers and the general population.
This issue has been known for years. The Danish environmental protection act defines hospitals which discharge large amounts of problematic substances as point sources, and local municipalities must order these hospitals to take steps to clean the wastewater efficiently before discharging to municipal sewers. However, options for solving the problem have previously been limited as an effective technology for treating the wastewater on a major scale has simply not been available.
Herlev Hospital on the outskirts of Copenhagen, Denmark, is one such hospital. One of Denmark's largest hospitals, it is currently (as of 2017) being expanded to offer approx. 82500 beds. On completion, the expanded hospital will employ approximately 6,000 staff.
The hospital offers a wide range of medical and surgical specialties. As a result, many different potentially problematic substances are used at the hospital on a daily basis and until recently were discharged to municipal sewers. For example, untreated hospital wastewater contains high concentrations of bacteria, viruses, and X-ray contrast media, and it contains pharmaceuticals in volumes that exceeded the effect limits for aquatic organisms by as much as factor 300.
In May 2014, however, Grundfos BioBooster delivered a unique wastewater treatment plant (WWTP) solution for Herlev Hospital that has since proved able to remove harmful substances so efficiently that the treated wastewater can be discharged directly to the aquatic environment without causing any problems.
The Grundfos solution
The BioBooster WWTP installed at Herlev Hospital through a public-private innovation project is the most advanced WWTP in Denmark. The scalable solution provides a very high level of water quality – close to drinking water.
The plant design is based on an MBR system (Membrane Biological Reactor) which consists of biological process tanks followed by rotating ceramic micro-filtration membranes for the retention of biomass. The process tanks are combined buffer and process tanks; here, the wastewater is treated by removing nitrogen and phosphorous to meet the strict requirements for the discharge of the effluent. The resulting particle and bacteria free water is then treated in a post-treatment line using ozone followed by granular activated carbon. UV light is used as an extra safety measure against pathogens before discharge. All process related air emissions are treated using photoionization, UV light and a catalyst before release in order to eliminate pathogens and odours from the air; it is therefore perfectly safe to operate the wastewater treatment plant close to the hospital and residential areas. All debris from inlet screens and excess sludge from the biological process are sent for incineration in order to completely eliminate any threats from these sources.
The BioBooster solution means great flexibility for Herlev Hospital as the solution handles all hospital wastewater in one centralised process. It is not necessary to separate wastewater containing problematic substances from other kinds of wastewater, and this makes it possible to move hospital wards without changing the piping. This could become a financial and practical benefit for the hospital and facilitates future planning efforts when building new wards and clinics. Also, the BioBooster solution is skid-based and can be scaled up and down as treatment requirements change.
The BioBooster solution also includes operation and maintenance. Under the terms of a service agreement between Herlev Hospital and Grundfos BioBooster, the latter assumes full responsibility for operating and servicing the plant 24/7/365. This means that complex and time-consuming tasks such as monthly inspections and status reporting to authorities are left to BioBooster service experts. The hospital only handles basic facility management tasks such as snow clearing and onsite cleaning. This ensures optimal operation, frees up hospital staff resources, and gives hospital management peace of mind.
An independent report from engineering consultancy company DHI confirms the efficiency of the BioBooster solution. The report concludes that the estimated risks involved in direct discharge of treated wastewater to the aquatic environment are negligible.
- 99.9% of problematic pharmaceuticals such as sulfamethoxazole, diclofenac, and capecitabin are removed.
- 99% of X-ray contrast media such as iomeprol are removed.
- No bacteria, viruses or oestrogen have been detected in treated wastewater.
- The BioBooster plant removes bacteria from plant air emissions.
In addition, sludge and other residual products are disposed of in an environmentally responsible manner. In other words, environmental issues are not simply shifted elsewhere but removed once and for all. "We are satisfied with the way it works. The plant performs according to expectations", says Chief Environmental Planner Ulf Nielsen of DHI who authored the report. Operations Manager Vibeke Prahl of Herlev Hospital is also happy with the treatment results and the collaboration with Grundfos BioBooster. "It works well, and it is something that we can all be very proud of. The collaboration with Grundfos has been very constructive", she says.
Local Government Denmark (KL), the association and interest organisation of Danish municipalities, currently regards the BioBooster solution as the best available technology (BAT) in the field. As such, the solution may become a landmark for other municipalities working to handle problematic hospital wastewater. "Municipalities are constantly searching for the BAT in this field, but until BioBooster appeared, we did not know which level of treatment we could require from the hospitals, and at what price", says Special Consultant Morten Beha Pedersen of KL. "We currently regard what’s happening in Herlev as BAT. If they can do it in Herlev, they can do it elsewhere, too." Ulf Nielsen agrees. "The plant is currently the only full-scale plant for hospital wastewater", he says. "The majority of the municipalities with hospitals currently regard the Herlev plant as the BAT."
Morten Beha Pedersen concludes that with the BioBooster solution, municipalities and hospitals alike suddenly find themselves in a position where they have the technology to solve wastewater issues. The solution at Herlev Hospital is a win-win situation that brings financial and practical benefits to several stakeholders. Most importantly, however, it proves that a reliable, proven, and efficient technology is now available that could make a major contribution to solving wastewater problems at point sources everywhere, and thereby benefit the environment.