Evaluation of sensor techniques for detection of contaminants in greywater from showers

Abstract

This thesis has been made in collaboration with the company Orbital Systems. The aim has been to optimize their product the Orbital shower, which is a circulating shower system.

The work evaluates different sensor techniques suitable for detection of contaminants in greywater. After a comprehensive literature study, three techniques; ultrasound, IR and impedance were further investigated and practically tested. Impedance values and IR absorbance were obtained from contaminants in still water, while the speed and frequency content of ultrasound was calculated using time of flight and FFT in both still and circulating water.

Test solutions used to evaluate the sensor techniques consisted of personal care products (shampoo, body wash and conditioner), human body contaminants and calcium. Varying concentrations of sodium chloride and cattle blood was used to simulate body fluids. Calcium was used to modify the hardness of water.

All three techniques were able to detect some contaminants and failed to detect others. The widest range of contaminants were detected when using a combination of IR and impedance. This combination did not only detect all test solutions but it could also to some extent quantify the contaminants. It is recommended that this combination should be investigated further. Technical parameters, advantages and limitations of each technique are discussed.

Lastly, an extensive recommendation was presented to Orbital Systems regarding how future research on sensor techniques should be conducted.

Popular Abstract

Optimization of sensors in recirculating shower system using IR, impedance and ultrasound.

Most innovative technology today contain at least one sensor of some sort. Sensors can measure movement, temperature or position to name a few. Limited research has been found on sensors regarding instantaneous water quality detection. This work is somewhat unique in this field.

Ever since the first water system was constructed in ancient Rome over 2000 years ago, water has been used in the same way. Water is taken from a big reservoir, used for one single purpose and then directly disposed. In ancient Rome, aqueducts led water from large lakes. Nowadays, pipes lead water from water treatment plants. Access to water is taken for granted in many parts of the world, but this is about to change. The outdated system where water is disposed immediately after use together with increasing population and climate change results in water scarcity in many parts of the world. One of the most affected countries, South Africa, has been forced to hold numerous nationwide campaigns acknowledging water use and trying to make the population waste less water.

Orbital Systems is an up and coming water saving company based in Malmö. Their aim is to change the way society uses water and help create a sustainable planet. Almost 30\% of the total water consumed by a person each day is used as shower water. This is the first problem that Orbital Systems has tackled with their creation the recirculating Orbital shower. The shower analyses the water before it reaches the shower drain and if deemed safe to reuse, gets drizzled back down on the user.

The brain of the product is a systems that 20 times every second measures the water and decides whether or not to reuse the water. This work has researched and evaluated different sensor techniques in order to improve the sensitivity of detection and thus further optimize the use of water during a shower session. Practical tests, using different possible shower contaminants, were carried out for the three most promising techniques. These three were ultrasound, IR and impedance. Ultrasound is commonly associated with imaging fetuses, IR is frequently used in heat cameras or motion sensors and impedance sensors are commonly found in several industry applications.

Each technique had their advantages and limitations and it was easy to conclude that none of the three could detect all tested contaminates. A combination of techniques is required for optimal detection and a sensor system using IR and impedance seems like the most promising combination.

• author: Bengtsson, Andreas and Andersson, Kalle
• supervisor: Martin Bengtsson; Michael Ridell
• organization: Department of Biomedical Engineering
• course: BMEM01 20201
• year: 2020
• type: H2 - Master's Degree (Two Years)
• subject: Technology and Engineering
• keywords: Greywater, Ultrasound, IR, Impedance, Detection, Shower
• language: English
• additional info: 2020-02
• id: 9012723
• date added to LUP: 2020-06-12 08:52:53
• date last changed: 2020-06-12 08:52:53