Water Management Systems: Overview, Design, and Functionality
Water Use and Treatment in the Paper Factory
A paper factory consumes a large quantity of water. The production process—cooking, refining, and forming the paper sheets—requires the pulp to be diluted, concentrated, and diluted again multiple times. In our case, this leads to a daily water usage of up to 2,000 liters for a production of 20 kg of paper per day.
Because we use this paper as the absorbent core of menstrual pads, maintaining high hygiene standards is essential. Good hygiene practices by operators alone are not sufficient if the water used in production is contaminated with bacteria or other pathogens. Therefore, we needed to build a reliable water treatment system that would ensure the cleanliness of the water used, while also meeting our constraints: low-cost, low-tech, and easy to replicate.
Instead of designing a system from scratch, we adapted an existing model developed by Aqueous Solutions. Their open-source system uses layers of stone, gravel, sand, and biochar to treat water, and they provide free documentation for two different installation sizes.
Our Adapted Water Treatment System
Below is a breakdown of the components in our installation:
1. Groundwater Storage Tank (1000L)
- Groundwater is pumped into this tank and flows by gravity into the next stage.
- The pump is controlled by a float switch that turns it on automatically when water levels fall below a certain point.
2. Gravel Filter (750L)
- Water enters from the bottom of the tank and flows through three layers: large stones, coarse gravel, and pea gravel.
- These layers help remove solid particles from the water, as they settle in the bottom of the tank.
- Every 2–3 months, a 2-inch pipe at the bottom is opened to flush out accumulated sediment.
- A floating valve at the inlet prevents overflow.
3. Slow Sand Filter (750L)
- Water flows into this tank from the top and passes downward through fine sand.
- Physical filtration removes fine particles, while a biofilm that forms in the top 1–2 cm of sand biologically treats pathogens and organic matter.
- Over time, the biofilm can reduce flow. To maintain efficiency, the surface of the sand is stirred every 3 months, and the tank is flushed from the top to remove suspended particles.
4. Biochar Filter (750L)
- Water flows from the top through a bed of biochar.
- The micropores in the biochar absorb dissolved chemical contaminants, while a thin biofilm further degrades some pollutants.
- This combination of adsorption and biodegradation effectively purifies the water.
5. Freshwater Storage Tanks (500L and 2000L)
- After treatment, clean water is first stored in a 500L tank at ground level.
- It is then pumped into a 2000L elevated tank (about 3 meters high).
- From there, water is distributed by gravity to the production process and toilets.
You can find further technical details and diagrams of the different tanks in the attached documents.
Several tests have been made to verify the efficiency of our system. The well water was not safe to drink, as E. coli was present, as well as a high quantity of heavy metal such as iron. Our system made the water safe to drink, according to the Nepali standard for safe drinking water, as well as the European Union standard.
This system is fairly easy to reproduce and does not require high tech equipment. Depending on how the system is built, only one pump (the one from the well) is needed, then gravitation is enough. In addition, if there are no tanks available to purchase, it is possible to build the tanks with bricks and cement. Regarding the gravels, their sizes are not fixed, if the size range is slightly higher or lower, it will still work. For example, in our case, as we couldn’t find gravels which were already distributed by size, we did it ourselves with mesh of different sizes.
The biochar can also easily be made directly on site. We made it ourselves with a Kon Tiki kiln, inspired from the work of the Ithaka institute: https://www.ithaka-institut.org/en/kon-tiki .
Key Insights Related to the Water Treatment System
We identified two critical aspects of our water treatment setup that significantly affect performance and reliability:
- System Maintenance is Essential
Regular maintenance is crucial to ensure both water quality and consistent flow rates. Key maintenance tasks include:
- Removing accumulated sediment from the gravel filter.
- Cleaning the biofilm layer on the surface of the sand filter.
- Replacing the biochar periodically, as its effectiveness diminishes over time.
- Cleaning and disinfecting storage tanks periodically to prevent contamination.
Neglecting these tasks can compromise the entire treatment process and reduce the availability of clean water for the factory.
- Pump and Automation Setup
Our factory is located on flat land, which required the installation of two pumps to ensure proper water flow throughout the system. Automating the process with float switches has proven especially helpful. It ensures a consistent water supply by automatically triggering the pumps based on water levels, minimizing the need for manual monitoring. A schematic of our float switch system is available in the documents section.
Wastewater Management: Current Challenges
We also built a wastewater treatment system, which is not yet functioning as intended and is currently under review for improvements.
- Current Setup:
- Wastewater collection is done through floor channels that direct water from the factory into a treatment sequence.
- The water first flows into a gravel filter tank, followed by a second tank with sand and gravel.
- The final stage sends the treated water into a soak pit, allowing it to return to the soil.
We do not reuse this water in the factory. Instead, we opted to release it back into the ground, cleaned. Indeed, being located closed to a river, we have enough water supply, and we were concerned about bacterial buildup in a closed-loop system.
- The issue
The soak pit currently does not absorb water quickly enough, leading to frequent overflows. We are actively seeking a more effective solution and will update this building block once a new system is in place.
