It has been pretty quiet lately on the blog front, so I thought I would post an update on the project. We want to use the markers we have tested and the new ones we have developed in E.coli as well as the microbial community in sewage to try and track human pollution through a catchment. To help us do this we need to know how long we expect E.coli and microbial communities to survive in river and sea water. Lots is known about the decay of E.coli in different environments, but very little is known about how other bacteria in sewage behave when they get into the natural environment.

For the experiment I treated myself to a Raspberry Pi (I always wanted an excuse to have a play with one) and with a cheap temperature probe, I built a little waterproof temperature sensor and data logger for the bargain price of £35.

Raspberry Pi 3 set up with a waterproof temperature sensor

Temperature sensors with data loggers usually cost around £100, the instructions to make your own are here. I also needed to monitor the light intensity, usually when degradation experiments are undertaken they are done in a lab with a constant amount of light. But this experiment was outside and so need to monitor how much light out samples were exposed to. To do this I used a pyranometer connected to a data logger and computer

The average water temperature in Northumberland during summer is a balmy 14oC, to keep the samples a constant temperature I used a water bath with a water heater to heat the water at night, and a water cooler to cool it during the day.

Just to make things a little sporting, none of the equipment is waterproof and Newcastle is not the city for bits of equipment that don’t like water. No expense was spared on waterproofing – a plastic box, a plastic sheet and a few bricks to hold it in place. People think that science is playing with glamorous bits of equipment but the reality can be different (and more fun!). Just to make sure everything was working, I tested the equipment for 1 week in the lab and for 1 week on the roof, exposed to the elements and everything seemed OK.

A computer and data-logger packed into an incredibly technical waterproof plastic box.

To set up the experiment I had to collect raw sewage from a local wastewater treatment plant, river water from the Seaton Burn catchment, sea water from the beach at Seaton Sluice and some cow poop from a local farm. After a 6am start and 2 hours of driving to collect everything I needed the stage was set. An hour of prep and the experiment was set up and running by 9am on the roof. After a day of lab work I headed back onto the roof to stir the bottles and check everything was running smoothly. Everything was not running smoothly. The thermostat on the heater had failed and heated the samples to about 400C. If the North Sea got anywhere near 400C swimming would be much more popular. After a serious amount of swearing I packed up the experiment and went home with my tail between my legs to wait for the next spell of good weather.

Luckily just 5 days of summer later it stopped raining and looked like we might see the sun once again. This time, with a new water heater installed, the experiment began without a hiccup.

I may have been a little obsessive, checking the second run a lot, even at dusk!


As I write this I am 5 days into the experiment. Samples are taken and analysed in the lab at 9 o’clock each morning on selected days. Processing samples all day is tiring, but tomorrow is not a sampling day so only 2 visits to the roof to stir the samples and in 10 days the experiment will be done and dusted, as long as nothing breaks…

The aim of this experiment is to feed into the assessment of pollution sources at Seaton Sluice to eventually make a plan of action of how we can ensure the water quality of the Seaton Burn continues to improve.