Exploring biological water treatment processes carried out in industries, at home.

Introduction From water-borne diseases spreading like wildfires, to unpleasant odors - the consequences of improper sewage treatment run rampant across urban and rural India, plunging the country into peril.

My project aimed at mimicking industrial sewage treatment processes using only household items. In turn, this would help understand the benefits and flaws of the current treatment systems. Such knowledge could act as a cornerstone in finding new solutions for viable sewage treatment in India, ranging from using anaerobic bacteria (bacteria that don’t require oxygen to respire) or systems that don’t require power to run.

To conduct this scientific experiment, I formulated a hypothesis, which stated “the number of bacterial colonies present in the effluent will decrease over the course of treatment, and the pH level of the water will move closer to 7”. As suggested in the hypothesis, my experiment used 2 independent variables, the pH of the water and the visual count of bacterial colonies (more on this later), to observe the progress of water treatment. I treated the water by growing aerobic bacteria (bacteria that utilize oxygen during respiration) in the effluent.

Preparing the Effluent at Home To conduct the experiment, the most fundamental element is the effluent. This was manufactured using blended kitchen waste, which was later left to rot in the sun. The following are the ingredients used to prepare the effluent:

  • Vegetable peels - 40 grams
  • Water - 750 milliliters
  • Basmati rice - 50 grams
  • Plain curd - 100 grams
  • Ensure protein powder - 10 grams The following ingredients were added in order to provide suitable nutrition for aerobic bacteria to grow in, which included trace amounts of metals along with organic matter and oxygen. The following mixture was blended until a smooth consistency was reached The mixture was then put into two separate bottles (bottle A containing 650 grams of effluent and bottle B containing 530 grams). Both bottles were covered with breathable tissue and rubberbands, and were left in the balcony for roughly 50 hours to let rot. IMG20240209170916 IMG20240209171100 IMG20240209174715

Mimicking Sewage Treatment Facilities In sewage treatment facilities, powerful churners pump air into the water, promoting growth of aerobic bacteria. Since air, and thus oxygen, is added into the effluent, aerobic bacteria can thrive, feeding on organic matter present, thereby partially cleansing the water.

To mimic this, I made 2 model churners that essentially carried out the same function as the air pumps in real facilities.

Churner A was made from a Milk Frother. The battery was removed and in its place two wires were connected to make its source of power from the socket rather than a battery, ensuring that the Frother remains churning even when nobody is monitoring it (a battery has the risk of dying out).

Churner B was made using a Motor Kit that involved building a spinning wheel, attaching it to a rod and connecting it to an AI system that could be coded using another device. Thus, after completing the short program that told the system to “set speed to 400% when turned on”, allowing the spinning wheel to act as a makeshift churner. IMG20240211124126 IMG20240211124059

Thus, the equipment pumped oxygen into the effluent over the course of 5 days, from which we could take samples over the days.

Sampling & Testing The following shows the method I used to sample and test the pH level and the bacterial colony count of the effluent sample for each of the 5 days -

  1. Sample Collection & Preservation Procedure
    • Measure 15 ml of effluent into a clean syringe after mixing the solution to gain a homogenous sample
    • Put the measured amount of sample into a vile or any other clean viable container. Close the lid on the container and ensure the sample cannot spill out by accident.
    • If the sample is not being tested as soon as it is collected from the effluent, put it in the fridge, or at around 4°C
    • Repeat this process to obtain samples from all 5 days of aeration
  2. Bacterial Colony Counting Procedure
    • Prepare agar plates and let set
    • Take the sample and pass through filtered paper and funnel to remove any solid particles
    • Take 5 ml of the filtered sample using a syringe and put it into a beaker. Take 5 ml of distilled water and add it to the sample
    • Add 5 ml of distilled water to the sample again (serial dilution) and swirl to mix
    • Sterilize inoculation loop by hovering over a flame until the wire turns orange from the heat
    • Dip the inoculation loop in the diluted sample and add a loopful of sample onto the top left quadrant of the agar plate. Using a back and forth motion, streak the sample in lines across the agar plate, sterilizing the loop (and letting cool for 5-10 seconds to ensure bacteria don’t die to high temperature) each time
    • Put a lid on the agar plate and leave it in a corner
    • Check the agar plate every 6 hours to note down if any bacterial colonies are visible. Repeat until 48 hours are over.
    • Repeat this experiment, of samples from all 5 days of aeration
  3. pH Testing Procedure
    • Use a calibrated pH meter to measure the pH of the sample for each of the 5 days of aeration

Conclusion The treatment of wastewater and sewage in India is an urgent matter that should be addressed in order to lower mortality rates to diseases, preserve aquatic ecosystems, and nurture a healthy environment around us. My proposed experiment takes into measure pH levels and visual bacterial colony counts to help track efficiency and progress of wastewater treatment by aerobic bacteria. My experiment was inconclusive due to practical limitations such as lack of equipment and certain time restrictions. However, it provided me with a great insight on the functioning of sewage treatment facilities around me, and has opened a pathway for me to explore alternative solutions to the lack of adequate sewage disposal in India.