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Research & understanding the problem

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1. Turbidity Case 3D files

Understanding the problem

The problem we have to address is about the quality of water. We first investigated the steps the water was going through from the source in the mountain to the tap. Here is how we can sum it up.

Testing the water

In order to put some data on the quality of water we decided to do some measurement about two aspects :

  • The turbidity of the water
  • The dissolved particles in water

What is TDS ?

TDS = Total Dissolved Solids, is a measure of the dissolved combined content of all inorganic and organic substances present in water. Typically, the higher the TDS value, the more substances dissolved in water. Hence, higher levels of Total Dissolved Solids (TDS) can indicate that water has more contaminants that can pose health risks.

Source : Seeed studio

For our application we used a seeed grove TDS sensor

What is Turbidity ?

Turbidity is the measure of relative clarity of a liquid. It is an optical characteristic of water and is a measurement of the amount of light that is scattered by material in the water when a light is shined through the water sample. The higher the intensity of scattered light, the higher the turbidity. Material that causes water to be turbid include clay, silt, very tiny inorganic and organic matter, algae, dissolved colored organic compounds, and plankton and other microscopic organisms.

Source : United states geological survey

For this measurement we didn’t have an appropriate sensor so we decided to make one.

Making of the turbidity sensor

To measure the turbidity we make a device that emits light and using a sensor, we measure the quantity of light received. We put our water sample between the light sensor and the light emission system and the more the water is turbid, the less light will go through.

It’s a simple model but it can give us more data to analyze the water quality.

BOM

  • 1x arduino nano
  • 1x breadboard
  • some jumper wires
  • 2x M3X6 screws
  • 1x a light intensity sensor
  • 1x 5mm LED and a 220Ω resistor
  • 1x 3d printed Case

The Case

To make the case we designed a part to fit the component and the water sample (in a water plastic cup)

Make files can be downloaded here

We 3D printed it following settings :

  • Material : PLA
  • Layer height : 0,3mm
  • infill : 5%

We then put all the components in the case (no glue needed)

Here’s about the wiring :

The code

void setup() {
  Serial.begin(9600);
  pinMode(3, OUTPUT);
  digitalWrite(3, HIGH);
}
void loop() {
  // read the input on analog pin 0:
  int sensorValue = analogRead(A3);
  // print out the value you read:
  Serial.println(sensorValue);
  delay(2000);
}

Here you have your homemade turbidity sensor :

Looking from the top we can see the beam of light is reduced with a more turbid water.

And we can see it in the values as well :

You can see in the serial monitor that we have a value of 36 with the clear water and a value of 445 with the turbid water. The lower the value, the clearer the water is.

NOTE : The values here are relative and not linked to real world units. It’s still a way to measure samples to compare the turbidity difference between them. Also for less interference we can put the whole device in a cardboard box to prevent external light from reaching the sensor.

Tests

To quantify the quality of the water we took samples at all the stages of the filtration system.

Here are the protocols for turbidity and TDS analysis :

TDS :

  • We put our reference water (mineral water bottle) in a cup
  • We shake the bottle with the sample
  • We place the sensor in the water
  • We wait for a stabilized value
  • We save the value
  • We put the sensor into the control water

TURBIDITY : - We put 2oz of water in the cup - We place the cup on top of test unit - We place the cardboard on top of the test unit - We wait for a stabilized value - We save the value - We remove the cardboard and the sample from the unit

Here are the values given by the test.

Results and conclusion

What we can learn from this is that the water according to TDS standards is of very good quality from the beginning to the end of the process.

We also noticed that going through the activated charcoal filter unit decreases the turbidity but increases the dissolved material in the water.

Our highest hypothesis on the color of the water is that; as the source is coming out from the ground in a pin forest. The tannin in the roots of the trees give it its color.

As tannin is an organic compound it’s no surprise that the water coming out the activated carbon filter is clearer as this filter is very good at removing organic compounds.

From the results of this analysis we can conclude that the water is a very high quality one. The water coming out of the tap is purer than the water bottle we buy. Our conclusion is that the problem really is about the aesthetic of water as the quality here is not the problem.

Last update: July 26, 2023