Bacterial water quality in recirculating and conventional showers from a stagnated building

Abstract

The modern shower was invented in the middle of the 19th century and is by far the most popular personal cleaning method in the west. One of the shortcomings of the conventional shower is that a majority of the water consumed is not dirty but goes out the drain all the same. Orbital systems AB has developed a recirculating shower as a modern and environmentally friendly alternative to the conventional shower. By recirculating the clean water in the shower, the user can save up to 90% of energy consumed and 80% of water used. Multiple studies have begun to explore conventional showers and their bacterial water quality. However, no such studies currently exist for recirculating shower systems. During the spring of 2020, three conventional and two recirculating showers located in an office building in Malmö municipal, were monitored for bacterial water quality. The goal was to study how the two different shower systems behaved in comparison to each other from a microbiological perspective. The bacterial water quality was defined as both the total bacterial flora in the water, measured with flow cytometry (FCM) and heterotrophic plate counts (HPC). As well as any presence of indicator bacteria measured with the Colilert 18 and Legiolert. During the spring of 2020 an unprecedented occurrence took place known as the Covid-19 pandemic. As a result of the pandemic around 80% of the personal occupying the office building started working from home, instead of coming into their offices. Water that was ordinarily being regularly used now stood stagnated in the pipes and in the shower heads. This presented a unique opportunity to monitor how water stagnation effects bacterial water quality in different shower systems. The study concluded that the bacterial water quality did change during the stagnation period. The total bacterial concentration increased in all of the shower system, as well as in the incoming water to the building from the distribution network. However, no increased health risk due to the presence of pathogens were detected in the water samples. Orbitals recirculating shower systems proved to be more resilient to bacterial growth due to stagnation, as opposed to their conventional counterpart. This indicates that recirculating showers could also prove to be more resilient to opportunistic pathogens as well.

Popular Abstract

The modern-day shower was invented in the middle of the 19th century and has since become a staple in the modern home. The average person in the west consumes around 75 liters of hot water while showering every day. If you ever observed the water that you shower in, it’s clear that not all the water that goes out the drain is dirty. In fact, a lot of people, this author included enjoys long showers, if only for the sake of the comfortable sensation of hot water streaming over yourself. For the last 150 years or so little changes have been made on the conventional shower, until now. In order to minimize waste of hot water, the company Orbital Systems AB came up with a revolutionary new concept for a shower. The world first recirculating shower.
The concept was based on technology utilized by NASA astronauts when showering in space. Water is a limited resource on a spaceship, to solve this problem the engineers at NASA developed a new concept on how to reuse shower water. The shower initially works as a conventional shower in that water is pumped into a shower head and then washes over the person operating the shower. But after it’s used rather than flushing it out, the water flows into a special drain. Here sensors analyze the quality of the water 20 times per second, in order to observe if the water is clean enough to be recycled. The water that is determined to be sufficiently clean, is then again pumped up into the shower head. But before it enters the shower head it flows through two disinfection barriers. The first barrier is a physical one in form of a micron filter and the second is a UV disinfection device, that radiates the water and kills the majority of the microbes present in the water. Finally, after the user is done showering, the recirculating shower system also flushes its system with hot water with automated programs called heat cycles. The heat cycles are performed mainly to clean out the pipes from any microbes that are present in the shower system. This concept is still quite new, and critics of the recirculating shower system are worried that recirculating shower systems is potential not as clean as conventional showers. Bacterial growth in showers is nothing new and it’s not too surprising if one thinks about it.
Conceptually a conventional shower works like this, after you shower you turn of the water flow. But the warm water is still present in the pipes and in the shower head it just sits still. Then when you turn on the shower again the first water that come out the shower has essential been sitting still for an extended period of time. It goes without saying that most people wouldn’t bath in warm water that has been sitting still for a couple of days, but with showers we don’t think about it. An experimental setup were two recirculating and three conventional showers were studied from February to May of 2020, was conducted in an office building in Malmö municipal. The goal of the study was to observe if recirculating showers are as clean as conventional showers from a bacterial perspective. However, in March of 2020 something unexpected occurred, the Covid-19 pandemic. The showers studied are located in an office building that once was full of employees, now stood nearly empty as 80% of the personnel had started working from home. This provided a unique opportunity to study what grows in frequently used shower systems when they are unused.
This study concluded that there was a definite increase in bacterial concentration. When comparing water from showers that are frequently used to when they stand still for extended periods of time. The conventional shower was also to a larger extent affected by the stagnation period then the recirculating showers. A possible reason for this is the disinfection steps installed in the recirculating showers, and primary because of the heat cycles that are regularly conducted in the shower system. The bacterial concentration did go up in total numbers, but what exactly did grow in this time period remains somewhat of a mystery without further investigation. What was concluded is that no harmful bacteria such as Legionella pneumophila and Escherichia Coli was detected in the shower systems. Meaning this report doesn’t indicate that the general public needs to be concerned about their next shower session. When they return to a building that has been shut down due to the Covid-19 pandemic.

• author: Strand, Filip
• supervisor: Catherine Paul
• organization: Applied Microbiology
• course: KMBM05 20201
• year: 2020
• type: H2 - Master's Degree (Two Years)
• subject: Biology and Life Sciences; Technology and Engineering
• keywords: Applied microbiology, Teknisk mikrobiologi
• language: English
• id: 9019154
• date added to LUP: 2020-06-18 13:06:19
• date last changed: 2020-06-18 13:06:19