Ensuring access to safe and clean drinking water is a fundamental aspect of public health. However, water quality can deteriorate significantly between treatment and consumption due to factors such as storage conditions and distribution systems. In regions like the United Arab Emirates (UAE), where many homes and facilities rely on roof or ground tanks for storing municipal water, maintaining these tanks is crucial to prevent contamination. This article delves into a case study that highlights the effectiveness of combining professional water tank cleaning with advanced point-of-use purification technology to achieve exceptionally high water quality.

Introduction

Water storage tanks are common in many parts of the world, especially in areas where municipal water supply systems are not fully developed or reliable. These tanks can accumulate sediment and biofilms over time, leading to bacterial growth and other contaminants. Even if the municipal supply is of high quality, the water can become compromised by the time it reaches the tap. This scenario is not unique to individual homes; it poses a broader challenge for businesses and government-managed buildings as well.

The case study focuses on a 5-bedroom villa in Dubai, where the homeowner faced significant water quality issues. The tap water had a metallic taste and visible suspended matter, prompting concerns about safety and palatability. To address these issues, two interventions were implemented: Saniservice’s comprehensive water tank cleaning and disinfection service, followed by the installation of the Aquaporin A2O Pure under-sink water purification system.

Problem Statement

The villa’s water storage tank had not been serviced in several years, creating ideal conditions for contamination. The harsh climate, characterized by high heat, and irregular maintenance allowed stagnant water and warmth to turn the tank into a breeding ground for microbes like Legionella and E. coli, as well as algae and molds. Sediment buildup from the incoming supply further deteriorated the water quality. These factors led to complaints of metallic-tasting water and visible particles in the tap water, indicating both chemical and physical contamination.

Initial water testing confirmed the extent of the problem. The tank’s water had a high heterotrophic bacterial count of 389 CFU/mL and a fungal count of 144 CFU/mL, exceeding what is normally expected in treated drinking water. For context, well-maintained distribution systems typically have heterotrophic plate counts below 100 CFU/mL and should not exceed 500 CFU/mL in 95% of samples. The significant microbial load suggested a loss of disinfectant residual and proliferation of biofilm. A visual inspection revealed the tank was filled with dirt and silt, explaining the turbidity and sediment in the tap water. This sediment also contributed to the metallic taste due to leaching of metals like iron from rust.

Initial Water Quality Testing Results

Before any intervention, comprehensive water testing was conducted to quantify the baseline water quality. Key parameters measured included:

• • Heterotrophic Bacteria Count: 389 CFU/mL, indicating significant microbial growth.
  • Fungal Count (molds/yeasts): 144 CFU/mL, consistent with mold observed in plumbing fixtures.
  • Turbidity: Approximately 4.5 NTU, well above the World Health Organization (WHO) guideline of <1 NTU for safe potable water.
  • Iron (Fe) Concentration: About 0.4 mg/L, above the aesthetic threshold where iron imparts a metallic taste.
  • Total Dissolved Solids (TDS): Around 360 mg/L, which is moderate and within acceptable ranges for treated water.

These findings confirmed compromised water quality: biologically active, visually turbid, and organoleptically unpleasant.

Intervention

The intervention was executed in two consecutive phases:

1. 1. Water Tank Cleaning and Disinfection

Saniservice performed an extensive cleaning and disinfection of the water tank and plumbing network. The process involved:

1. 1. Isolation and Drainage: The main water supply was shut off, and the storage tank was fully drained.
   2. Mechanical Cleaning: Technicians manually scrubbed and vacuumed out sludge, dirt, and silt using a plant- and mineral-based cleaning agent.
   3. Chemical Disinfection: A Dubai Municipality-approved bio-sanitizer was applied to inactivate remaining microorganisms. The tank was refilled and chlorinated to achieve a free chlorine residual of 20-50 mg/L for shock treatment.
   4. Fixture and Pipeline Treatment: Taps and showerheads were individually cleaned and disinfected to prevent recontamination.
   5. Flush-Out: The chlorinated water was flushed out completely, and the tank and pipes were refilled with fresh municipal water.

This comprehensive cleaning regimen physically removed sediments and biofilms and chemically inactivated microbes throughout the system.

1. 2. Aquaporin A2O Pure Installation

Following the tank service, an Aquaporin A2O Pure under-sink water purification system was installed at the kitchen tap. This advanced reverse osmosis (RO) system incorporates biomimetic technology using specialized RO membranes with Aquaporin Inside, which mimic the selectivity of living cells. The system includes a three-stage filtration:

• • Sediment/Carbon Pre-filter: Traps sediments, chlorine, and organics.
  • Aquaporin RO Membrane Cartridge: Removes dissolved solids and contaminants.
  • Carbon Post-filter: Polishes taste and removes residual odor.

The system operates on normal line pressure and can produce about 2 liters per minute of purified water on demand. It achieves high removal rates (>99%) for dissolved solids and impurities, including heavy metals, nitrates, sulfate, chlorine, disinfection by-products, and emerging contaminants like PFAS and microplastics.

Post-Treatment Water Quality Results

After both interventions, water samples were collected for analysis. The post-treatment testing included microbiological and physicochemical parameters, focusing on the same indicators measured initially.

Microbial Results

• • Heterotrophic Bacteria Count: Dropped from 389 CFU/mL initially to just 4 CFU/mL after cleaning (a reduction of ~99%) and to 0 CFU in the RO purified water (essentially a 100% removal of viable bacteria).
  • Fungal Count: Completely eliminated; none were detected in either the post-cleaning or RO water.

These results confirm the effectiveness of the shock chlorination and sanitization procedure in disinfecting the tank and plumbing. The absence of any indicator of fecal contamination, combined with the near-sterility achieved, means the water met international microbiological standards for drinking water safety.

Physical/Chemical Results

• • Turbidity: Reduced from ~4.5 NTU to 0.5 NTU after tank cleaning and further down to <0.1 NTU after RO (essentially crystal clear).
  • Iron Concentration: Dropped from about 0.4 mg/L to 0.05 mg/L after cleaning and was undetectable after RO.
  • Total Dissolved Solids (TDS): Remained around 355 mg/L after cleaning but dropped to ~10 mg/L after RO, indicating extremely pure water.

The water’s chemical profile showed significant improvement in aesthetic parameters, with the elimination of the metallic taste and odor.