1. Introduction
Polyhouse cultivation requires controlled environmental conditions to ensure optimal crop growth. Cooling pads are widely used in evaporative cooling systems to regulate temperature and humidity. However, the continuous circulation of water across the pads, combined with sunlight exposure, creates favorable conditions for algae growth.
Why algae is a problem:
1. Clogs pad pores, reducing airflow.
2. Decreases cooling efficiency.
3. Requires frequent cleaning and replacement, raising maintenance expenses.
Therefore, effective algae control is essential for sustainable polyhouse operations.
2. Problem Statement
Cooling pads in polyhouses frequently face algae growth, especially during summer when warm temperatures and high humidity accelerate microbial growth.
- Existing methods (like manual cleaning) are labor-intensive, temporary, and costly.
2. A need exists to identify cost-effective chemical methods for long-term algae management.
3. Objectives
- To study the factors contributing to algae growth on cooling pads.
2. To evaluate lime treatment as a pH-based method for algae control.
3. To evaluate bleaching powder treatment as a chlorine-based method for algae control.
4. To design an experimental setup simulating actual cooling pad conditions.
5. To compare results and recommend the most effective treatment for farmers.
4. Experimental Setup
Materials Required
- Tulu water pumps (for continuous circulation)
- 2 plastic buckets (capacity: 15 liters each)
- cooling pads
- Bleaching powder (Ca(OCl)₂) – chlorine content – 30 %
Experimental Setup for Buckets
- Two plastic buckets (15 L each) were prepared:
- Bucket A (Treated): Water treated with Bleaching powder
- Bucket B (Control): Untreated water.
- Cooling pad samples were placed above each bucket.
- Tulu pumps circulated water continuously from the buckets to the top of the pads, simulating real polyhouse cooling systems.
- Both setups were kept in natural light to encourage algae growth.
Bleaching Powder Treatment
Calculation:
Bleaching powder containing ~30% chlorine
We want 100 ppm and 1 gm/lit Conc. of chlorine
Therefore , 0.1 %
Required available chlorine = 15 lit × 1 gm/lit =15 gm
Bleaching powder required = 15 / 0.30 = 50 gm
Bleaching powder was dissolved and added to Bucket A (Treated), while Bucket B remain untreated.
Pad Size : Height (H) = 40 Cm = 0.40 m
Width (L ) = 32 Cm = 0.32 m
Area (A) = Height x Width
A = 0.40 x 0.32 = 0.128 m 2
Pad Area = 0.128 m2
Methods to Measure Algae Growth
1. Visual Observation & Scoring (Simple, Low-Cost)
Inspect the cooling pad surface daily.
Assign scores based on algae coverage:
Algae Growth Observation :
Please refer to the above link to view further observations :
| Date | Day | Treated Water(Bleaching Powder) | Untreated Water |
| 13/09/2025 | Day 1 | No algae visible | No algae visible |
| 14/09/2025 | Day 2 | No algae visible | No algae visible |
| 15/09/2025 | Day 3 | No algae visible | Slight green tint at Right side edge of pad |
| 16/09/2025 | Day 4 | No algae visible | Tint spreading, still < 5 % . |
| 17/09/2025 | Day 5 | No algae visible | Tint spreading, still < 10 % . |
| 19/09/2025 | Day 6 | No algae visible | Slight algae in middle section |
| 20/09/2025 | Day 7 | No algae visible | Slight green tint at left side edge of pad |
| 21/09/2025 | Day 8 | No algae visible | Dark green tint at right side of pad |
| 22/09/2025 | Day 9 | No algae visible | Dark green tint at left side of pad |
| 23/09/2025 | Day 10 | No algae visible | Small algae patch visible at middle section, slight green tint (<5% area) |
| 24/09/2025 | Day 11 | No algae visible | algae patch visible at middle section, slight green tint (< 10 % area) |
| 25/09/2025 | Day 12 | – | – |
| 26/09/2025 | Day 13 | No algae visible | Algae presence increasing gradually, not easily visible on surface . |
| 27/09/2025 | Day 14 | No algae visible | Algae presence increasing gradually, not easily visible on surface . |
| 28/09/2025 | Day 15 | No algae visible | Algae still not clearly visible on surface, starting to spread gradually |
| 29/09/2025 | Day 16 | No algae visible | Algae growth increasing slightly, still not easily seen |
| 30/09/2025 | Day 17 | No algae visible | Algae spreading further, minor patches visible on pad edges. |
| 01/10/2025 | Day 18 | No algae visible | Algae present in more areas, but surface largely looks clean. |
| 02/10/2025 | Day 19 | – | Observation not recorded / no significant change noted. |
| 03/10/2025 | Day 20 | No algae visible | Algae now clearly visible on pad surface, covering noticeable sections |
| 04/10/2025 | Day 21 | No algae visible | Algae coverage increased, surface largely covered with green patches |
| 05/10/2025 | Day 22 | No algae visible | Algae coverage increased slightly ,overall condition remained similar |
This method is subjective but easy and practical for farmers.
2. Measuring Airflow with Anemometer
Why?
Algae clog the pores of cooling pads.
When pores are blocked, airflow through the pad decreases.
An anemometer (which measures wind speed/air velocity) can directly quantify this effect.
How to Use It
Place the anemometer behind the cooling pad (air outlet side).
Measure air velocity (m/s) at the start (Day 0 – Onwards) when pads are clean.
Compare airflow reduction in treated water or untreated water
Record air velocity values (m/s) in a table :
Please refer to the below link to view further observations
| Day | Date | Control (Untreated Water) Velocity (m/s) | % Reduction | Treated (Bleaching Powder) Velocity (m/s) | % Reduction |
| 0 | 13/09/2025 | 1.57 | 0% | 1.57 | 0% |
| 1 | 14/09/2025 | 1.57 | 0 % | 1.57 | 0 % |
| 2 | 15/09/2025 | 1.55 | 1.27 % | 1.57 | 0 % |
| 3 | 16/09/2025 | 1.55 | 1.27 % | 1.57 | 0 % |
| 4 | 17/09/2025 | 1.55 | 1.27 % | 1.55 | 1.27 % |
| 5 | 19/09/2025 | 1.52 | 3.18% | 1.53 | 2.55 % |
| 6 | 20/09/2025 | 1.5 | 4.46 % | 1.53 | 2.55 % |
| 7 | 21/09/2025 | 1.48 | 5.73 % | 1.53 | 2.55 % |
| 8 | 22/09/2025 | 1.47 | 6.37% | 1.52 | 3.18 % |
| 9 | 23/09/2025 | 1.45 | 7.64 % | 1.52 | 3.18 % |
| 10 | 24/09/2025 | 1.38 | 12.10 % | 1.51 | 3.8 % |
20 September 2025 :
On 20th September, there was a discussion with Dixit Sir about the algae experiment. Sir checked the observations of the past 7 days and told me to continue taking observations.
1 Oct 2025
Dixit sir told me to measure the airflow of the old polyhouse cooling pad with the help of an anemometer. I measured it in 5 sections as follows :
| Section of cooling pad of old polyhouse | Readings (ft/min) | Mean (ft/min) | Mean (m/s) |
|---|---|---|---|
| Section 1 | 106, 138, 157 | 133.7 | 0.68 |
| Section 2 | 204, 170, 147 | 173.7 | 0.88 |
| Section 3 | 87, 80, 108 | 91.7 | 0.47 |
| Section 4 | 123, 140, 90 | 117.7 | 0.60 |
| Section 5 | 0, 0, 87 | 29.0 | 0.15 |
| Overall | — | 109.1 ft/min | 0.55 m/s |
Cooling pad observation :
| Section of cooling pad of old Polyhouse | Airflow (m/s) | Observed Algae Growth | Observation/Interpretation |
|---|---|---|---|
| Section 1 | 0.68 | Moderate | Airflow is decent, algae growth is moderate. |
| Section 2 | 0.88 | Low | High airflow reduces algae accumulation. |
| Section 3 | 0.47 | Moderate | Lower airflow than Sections 1 & 2, moderate algae growth. |
| Section 4 | 0.60 | Moderate | Airflow is sufficient, algae growth not severe. |
| Section 5 | 0.15 | High | Very low airflow → stagnant area → algae growth highest. |
| Overall | 0.55 m/s | – | Average airflow moderate; algae growth varies by section. |
10 Oct 2025
On 10th October, Dixit sir checked the cooling pad of the algae experiment. In visual observation, the algae growth is clearly visible, but there is not much change in the air flow on a daily basis, so sir told me to take weekly observations.
26 OCT 2025
On 26th October, a discussion was held with Dixit Sir and Abhijeet Sir ,the algae experiment was discussed in detail. In this experiment, the final calculations, conclusions, or results could not yet be obtained because the algae growth on the cooling pad was not as expected. Although the algae have fully covered the surface of the cooling pad, the holes are still not completely blocked. Therefore, to enhance and accelerate the algae growth, various measures—such as the application of fertilizers or other nutrients—were discussed with the sir during the meeting .
31 Oct 2025
Objective: To boost algae growth for comparison with the bleaching powder treatment.
- Urea: 1 gram per liter → 20 grams for 20 L
- SSP: 1 gram per liter → 20 grams for 20 L
