According to the United Nations Department of Economic and Social Affairs, it is estimated that by 2050 there will be 2.5 billion people added to urban areas. This will account for 68% of the world’s population, with the majority of growth occurring in China, India, and Nigeria. In order to accommodate this increasing population, there will be a demand for more buildings and infrastructure, roads and highways as well as cars to transport the masses. The effects of urbanization place serious stress on the bodies of water used to sustain the citizens of these large cities. According to the United States Environmental Protection Agency, pollution in urban settings primarily comes from the following sources (EPA):
• Oil, grease and toxic chemicals from motor vehicles
• Pesticides and nutrients from lawns and gardens
• Viruses, bacteria and nutrients from pet waste and failing septic systems
• Road salts
• Heavy metals from roof shingles, motor vehicles and other sources
• Thermal pollution from impervious surfaces such as streets and rooftops
In order to assist government officials and city planners in deterring the negative effects that urbanization has on water as well as to provide valuable information to the people in these areas regarding water quality and safety, we have designed a system of sensors which can monitor key parameters that will indicate water quality, and relay information quickly and effectively to the end user using the Internet of Things (IoT).
Hybrid low-power wide-area mesh IoT network
In this work, we propose a lightweight, hybrid mesh network combining the advantages of WPAN’s ultra-low power consumption (ANT) and LoRaWAN’s wide area coverage by integrating LoRa (physical layer of LoRaWAN) and ANT. Our IoT solution features are as follows:
• Large coverage: up to 10 km in urban environment
• Power efficient: 3 to 5 years of operation with 2 AA batteries
• Low cost: each wireless module would cost around $10, at high manufacture volume
To implement the proposed hybrid network and enable the data collection with different sensors for different applications, we have designed and manufactured our own hardware modules. Each wireless module will be packaged in waterproof containers that can be faced with many sensors depends on the different applications.
A prototype of our network consisting of more than 15 sensors has been deployed around the Purdue University campus (West Lafayette, USA) for more than 6 months, covering a wide area of almost 3 km2. Real-time data and visualization can be accessed from the following link:
There are several parameters used in practice to determine water quality, however, not one parameter alone can be taken as the best indicator. In order to really understand whether changes in this ecosystem are indicative of pollution, it is necessary to understand which combination of parameters paint the full picture and what changes to look for.
• Conductivity: Used as a measurement of water quality along with temperature. An abnormal increase in conductivity can be attributed to dangerous levels of ions from pesticides, fertilizers, or chemicals. A sudden decrease in conductivity can be attributed to the presence of oils in the water.
• pH: scale of acidity of a solution. High levels of chemicals in the water typically result in a decrease in pH.
• Turbidity/Total Dissolved Solids (TDS): A measurement of the total amount of particles in a solution, which can indicate the presence of heavy metal particles and sediments in the water.
• Nitrate/Phosphate: Two main pollutants from fertilizer runoffs.
Currently, there is no technology able to measure all of these parameters simultaneously in the water. By integrating commercially available TDS, temperature, and Turbidity sensors, as well as our own custom-made nitrate, phosphate, pH, and conductivity sensors, we will be able to monitor changes in water quality anywhere in real time.
The smart sensors are manufactured at Purdue’s Birck Nanotechnology Center. Our custom Roll-to-Roll processing machine makes fabrication of these sensors as affordable as possible, bringing the cost down to ~30¢ each. Their flexible design makes them a versatile tool, deployable in both land and water. So far, nitrate and phosphate sensors have been developed. Future work is focused on pesticide and heavy metals detection in water.
Impact around the world!
This novel design could truly impact the way people assess water quality and design urban planning. Using low-power wireless tech such as Lora and ANT, enable easy integration of new and cheap sensors to measure environmental factors. By providing a collection of real time data, people would develop a better understanding of how their water systems are affected. The affordability of the sensors would allow for easy replacement and maintenance of the devices and would make it accessible to communities all over the world. LoRa is a versatile tool, which enables easy integration of new sensors, as the technology in this area is sure to improve.