A new wastewater treatment plant rids a Danish hospital’s wastewater of medicinal residues that ordinary sewage treatment cannot handle.
HOSPITAL wastewater contains a lethal mix of everything from medicines to pathogens – stuff which cannot be removed in conventional wastewater treatment plants. When such effluent flows into rivers and oceans, it might cause adverse effects on the fauna.
Estrogens, for example, can cause hermaphroditic fish, while some painkillers are poisonous to trout, and certain pharmaceuticals can affect fish and bird behaviour. In the United States, scientists have documented cases of intersex in fish – such as males displaying female characteristics, including carrying eggs – in streams downstream of wastewater treatment plants.
Despite the possible hazards, pharmaceutical-laden effluent remains unregulated in most countries and is allowed to flow into public sewers.
Nevertheless, some European countries, including Denmark, are beginning to scrutinise the threat it poses.
At its second biggest medical facility, Herlev Hospital near Copenhagen, a new treatment plant has been built to handle this type of waste. The 1,000-bed hospital discharges some 490 cu m of wastewater everyday, which contains residues of some of the 1,000 drugs which it uses. With expansion plans for an additional 60,000 sq m of space by 2017, its effluent is projected to hike from the current 150,000 cu m a year to 190,000 cu m.
“Most of the 1,000 drugs are harmless but some are hazardous,” says project engineer Jess Krarup.
The new treatment plant is designed by Grundfos BioBooster, a subsidiary of Grundfos, a global supplier of water and wastewater systems. Lab-scale tests started in 2012 and paved the way for the set-up of the membrane bioreactor (MBR) plant in Herlev Hospital in May 2014.
At the heart of the treatment process is a series of rotating ceramic membranes which filter particles and bacteria from the wastewater. This is followed by ozone and activated carbon treatments to eliminate pharmaceutical residues.
A final UV treatment gets rid of residual ozone and any remaining pathogens, and renders the treated water clean enough to drink or be discharged into streams.
Sludge from the treatment process is sent for incineration as it contains pharmaceutical by-products.
So far, the technology shows very high pharmaceutical removal rates, with 90% of residues (100 of the most hazardous compounds were analysed) being reduced to below detection limits, according to Dr Jose Antonio Gil Linares, application specialist at Grundfos.
As for the pharmaceuticals which cannot be removed, Krarup explains: “It’s a question of economics. It is too expensive to clean everything but we try to go below the limits. This plant shows that it is possible to get rid of pharmaceuticals and it can be done in other hospitals too.”
The plant cost 42mil kroner (RM23.1mil). “Construction of a new building and design alterations had increased the cost. Otherwise, it would be possible to bring it down to 25mil kroner (RM13.75mil),” says Krarup.
He says the hospital is currently spending more to handle its wastewater – 36 kroner (RM19.80) per cu m compared with 25 kroner (RM13.75) previously – as it is still discharging the treated wastewater to municipal sewers (it pays a fee to do that). Cost is expected to drop when the hospital obtains a permit to reuse the water for cooling and technical purposes or to discharge to a water body, which saves it drainage fees.
Danish municipalities have collectively set maximum acceptable concentrations for 36 pharmaceuticals in hospital wastewater that is discharged into public sewers. There is also a tool for ranking hospitals as major, medium or minor sources of wastewater so that regulatory focus is on significant sources. However, there is still no regulated or standardised method to handle hospital wastewater.
Linares says plants which can treat such wastes are unique even in Europe. Aside from the one in Herlev, there are only two in Germany and one in The Netherlands. He says there are currently no limits on allowed discharges and hospitals are not obliged to specially treat their wastewater. “But now that the technology is available, we expect the Danish Government to impose legislations requiring hospitals to do so.”
He says it is possible to retrofit existing wastewater treatment plants to incorporate the MBR system to remove pharmaceutical residues. However, a conventional plant handles some 75,000 cu m of effluent a day, so the cost will be high if it uses the MBR process.
Designed in modular style, the MBR plant is flexible and compact, and can easily be set up. On-site treatment is ideal as the wastewater is received directly from the hospital and is not mixed with wastewater from public sewers. This makes it possible to specifically target the substances in hospital effluent.
Linares shares that only 5% of the total pharmaceutical by-products in wastewater is generated by hospitals; the bulk of it is from households. This means that treatment plants should also adopt better processes which can remove medicines and pathogens from wastewater.
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