Every day, hospitals across Iran consume enough water to fill an Olympic-sized swimming pool, generating a complex chemical and biological cocktail that flows unseen beneath our feet.
When we think of hospitals, we imagine sterile environments, life-saving medicines, and dedicated healthcare professionals. Rarely do we consider what happens after the water drains from surgical suites, laboratories, and patient rooms. This invisible byproduct of healthcare—hospital wastewater—carries within it clues about our medical practices, their environmental footprint, and potential threats to public health.
At Babol University of Medical Sciences in northern Iran, scientists have turned their attention to this often-overlooked aspect of healthcare. Their investigations reveal a complex story of how human health and environmental health are inextricably linked. The wastewater flowing from hospitals tells a tale of modern medicine's triumphs and challenges—of life-saving treatments leaving behind traces that may threaten ecosystems and communities downstream.
Hospital wastewater is qualitatively different from what flows from our homes. While municipal wastewater contains typical domestic pollutants, hospital effluent represents a complex mixture with potentially hazardous components. Imagine everything that goes down the drains in a healthcare facility: disinfectants from cleaning, pharmaceutical residues excreted by patients, chemical reagents from laboratories, and heavy metals from various medical applications.
One of the most concerning aspects is the presence of pharmaceutically active compounds (PhACs) including antibiotics, painkillers, and chemotherapy drugs that patients excrete.
Annual organic loading rate from BUMS hospital wastewater 3
To understand the real-world characteristics of hospital wastewater, researchers conducted a comprehensive study of hospitals affiliated with Babol University of Medical Sciences (BUMS) in Iran. This investigation provides a revealing snapshot of what flows from healthcare facilities in the region.
Between June and August 2013, researchers collected ninety-six composite wastewater samples from four teaching hospitals in Babol. This summer sampling was deliberate—to avoid dilution effects from rainfall that might skew the data 3 .
96 composite wastewater samples collected from 4 hospitals
Physical-chemical parameters, organic matter indicators, nutrient content, microbial content, and heavy metals
Atomic absorption spectrometry for heavy metal analysis and standard microbial techniques
June - August 2013
96 composite samples
4 teaching hospitals
The data painted a concerning picture of wastewater characteristics exceeding regulatory standards. The volume alone was significant—with total wastewater production reaching 169,263 m³ annually, carrying an organic loading rate of 62,966 kg per year 3 .
| Parameter | Average Value | Minimum | Maximum |
|---|---|---|---|
| pH | 7.6 ± 0.4 | 6.9 | 8.3 |
| BOD₅ (mg/L) | 372 ± 173 | 161 | 648 |
| COD (mg/L) | 687 ± 231 | 379 | 1,187 |
| TSS (mg/L) | 289 ± 132 | 108 | 538 |
| TKN (mg/L) | 15 ± 5.5 | 8.1 | 26.5 |
| Total Phosphorus (mg/L) | 2.2 | 0.8 | 5.0 |
The organic pollution parameters are particularly telling. The COD values (687 ± 231 mg/L) significantly exceeded what's typical for municipal wastewater, indicating a high load of oxidizable organic compounds. The BOD₅ values (372 ± 173 mg/L) similarly pointed to substantial biodegradable organic content 3 .
Perhaps most alarming were the microbial findings. The total coliform counts reached 5.4 × 10⁸ MPN/100 mL, with total heterotrophic bacteria at 2.6 × 10¹⁰ CFU/mL—numbers that indicate massive microbial contamination including potentially pathogenic organisms 3 .
The heavy metal analysis revealed a concerning presence of various metals, with iron and zinc appearing in the highest concentrations. These metals likely originate from various medical, laboratory, and maintenance activities within the hospitals 3 .
| Heavy Metal | Average Concentration |
|---|---|
| Iron (Fe) | 2.1 mg/L |
| Zinc (Zn) | 429 μg/L |
| Copper (Cu) | 49 μg/L |
| Chromium (Cr) | 34 μg/L |
| Nickel (Ni) | 30 μg/L |
| Lead (Pb) | 26.5 μg/L |
| Mercury (Hg) | 7.5 μg/L |
| Cobalt (Co) | 3.7 μg/L |
| Cadmium (Cd) | 2 μg/L |
Understanding wastewater composition requires specialized equipment and methodologies. Researchers investigating hospital effluent employ a diverse toolkit of analytical approaches:
This sophisticated technique enables precise measurement of heavy metal concentrations at very low levels 3 .
Used for quantifying total coliform bacteria using Most Probable Number (MPN) statistics 3 .
Employed for determining total heterotrophic bacteria counts, measured as Colony Forming Units per milliliter (CFU/mL) 3 .
Established protocols for analyzing conventional parameters like BOD₅, COD, TSS, TKN, and TP 3 .
Modern molecular technique to identify diverse microbial communities and pathogens in wastewater 6 .
The findings from Babol take on greater significance when viewed in their environmental context. The study concluded that "most of the qualitative indices evaluated in wastewater effluent of hospitals of BUMS were higher than effluent discharge standards of Iran Environment Protection Agency" 3 .
This untreated or inadequately treated wastewater eventually reaches the Babol Rood River and ultimately flows into the Caspian Sea, creating potential ecological consequences far beyond the hospital walls 3 .
Hospital wastewater contains various pathogenic microorganisms that conventional treatment doesn't always eliminate. Research has shown that even treated wastewater can contain pathogens like Arcobacter species (causing human and animal diarrhea) and Acinetobacter species (notorious for hospital-acquired infections) 6 .
When these pathogens enter aquatic ecosystems, they can survive and spread. Studies of wastewater discharge into marine environments have found that while pathogen biomass decreases with distance from the discharge point, some remain detectable up to 1,000 meters from shore 6 .
Perhaps the most insidious threat lies in the contribution of hospital wastewater to the spread of antibiotic resistance. Hospitals are hotspots for antibiotic-resistant bacteria (ARB) and antibiotic-resistant genes (ARG). These can survive conventional wastewater treatment and enter the environment, where they may transfer resistance genes to other bacteria 2 5 .
This creates a dangerous cycle: antibiotics used in healthcare lead to resistant bacteria in patients, which enter wastewater, potentially spread resistance in the environment, and may eventually recolonize humans through contaminated water or food.
Addressing the challenge of hospital wastewater requires both technological solutions and systemic changes in how we manage water resources in healthcare facilities.
Conventional wastewater treatment methods, while effective for typical municipal wastewater, often struggle with the complex mixture of pollutants in hospital effluent. Research points to several promising approaches:
These systems combine biological treatment with membrane filtration, achieving more than 80% removal of conventional parameters like BOD and COD 5 .
Techniques like ozone treatment and UV irradiation can break down persistent pharmaceutical compounds that resist biological degradation 5 .
Specially designed anaerobic reactors show promise for degrading certain antibiotic classes by harnessing specific microbial communities 2 .
A 2025 study highlights that water crises in hospitals extend beyond wastewater treatment to include supply challenges. Aging infrastructure, natural hazards, and planning deficiencies can disrupt water access, compromising both medical services and wastewater management 4 .
The investigation into Babol's hospital wastewater reveals a critical intersection between healthcare delivery and environmental protection. Hospitals, dedicated to healing, must also minimize their environmental footprint to avoid contributing to disease through polluted water.
The characteristics of wastewater from BUMS hospitals—high organic load, significant microbial contamination, and detectable heavy metal content—highlight the need for specialized treatment approaches tailored to hospital effluent. As research continues, solutions are emerging that can break down complex pharmaceuticals, inactivate resistant pathogens, and remove hazardous chemicals.
The challenge of hospital wastewater represents an opportunity to reimagine healthcare as not only therapeutic for individuals but also protective of the ecosystems that sustain us all. By applying scientific insight, technological innovation, and responsible management, we can create a future where healthcare's healing mission extends beyond hospital walls to the water that connects us all.