unintended consequences

We are all hindered by unintended consequences, Sweden one might argue a global leader for harvesting leftover heat was hamstrung by the law which prevented other suppliers accessing the district heating grid, but that changed when a law was passed last year that allows outside suppliers to deliver heat through the district heating grid. Now the town of Kiruna in northern Sweden can use waste heat from their local industry to cheaply heat homes, a neat solution when the mercury hits -30 Deg C in winter. Details are scarce in the Guardian article [1] however using waste heat whether from industry or power generation is cost-effective when the distance (where increasing distance equates causing increasing heat loss) between the source and end-user is not great.

Less commonly known is that waste heat can be used in the tropics to drive air conditioning, necessary in large parts of Asia. Low grade heat energy is often dumped into rivers or the sea, instead it can be used to change the concentration of liquid salt, e.g. lithium bromide, creating cold water for comfort cooling.

[1] http://www.theguardian.com/sustainable-business/2015/may/01/leftover-industrial-heat-to-warm-swedens-chilly-northern-city

Hong Kong Baptist Hospital Legionella Discovered April 2015

Legionella Risk assessment Hong Kong

A 60 year male patient attending Hong Kong Baptist Hospital (HKBH) contracted a nosocomial infection, the potentially fatal Legionnaires Disease (LD). After the patient was diagnosed, EMSD sampled from both his home and the hospital. His home was negative, but the hospital water supply tested positive, four samples with Legionella pneumophila serogroup 1 (Lp1) with 0.3 to 2.3 colony-forming units per millilitre (cfu/ml) reported. {1}.

Remember the infectious dose for LD is still unknown, but could be as little as 1 cfu based on a case where Legionella was contracted 6 km away from the source.

The HKBH fresh (potable) water tank was reported negative for Lp1. Since the fresh water tank in an ‘occupied’ hospital would typically have a high turnover, a negative result would be expected because there is little risk of stagnant water. Therefore, in this case the root cause must be within the water distribution piping.

Interestedly, three environment swabs, collected from HKBH, also tested positive for Lp1, but as usual no details were reported. We can only speculate these could be swabs from surfaces in and around the shower and toilets areas.

Approximately month after first exposure, around 4 April 2015, it is reported that the EMSD visited the site today, presumably the date of the government press release 5 May 2015 {1} , recommending I quote ‘….disinfection of the relevant water system.’ amongst other measures. The number of patients who may have been exposed to the risk of contracting Legionella during that month is unknown, and attempting to disinfect the water system in a working hospital full of patients will be a challenge. In the report there is no mention of any earlier risk assessment.

This case is particularly troubling because Legionnaires Disease (LD) was contracted in the hospital environment, and it seems from the report that approx. one month lapsed between infection and disinfection.

[1] http://www.chp.gov.hk/en/view_content/39502.html