With the global population on the rise, the demand for food is increasing. Meeting this demand requires sustainable agricultural practices, including water management. Reusing industrial and municipal wastewater for irrigation presents a practical solution, but while this practice mitigates the environmental and economic burdens of agriculture, it also brings its own significant environmental challenges.
Wastewater is exactly that: water that has been used in the home, a business or industrial process. It’s not necessarily clean or the ideal water for agricultural irrigation, but 65 percent of irrigated lands around the world are dependent on wastewater, and 82 percent of these lands are found in regions where less than 75 percent of wastewater is treated.
Wastewater can be polluted with heavy metals or dyes from industrial applications, for example, but a growing concern is pharmaceutical pollution found in both treated and untreated wastewater. The persistence of pharmaceuticals in the environment is well-documented, and these pollutants have far-reaching implications, including the potential to impact soil health, plant nutrient uptake and the development of antimicrobial resistance across the wider food chain.
The introduction of pharmaceuticals into the environment predominantly occurs through treated wastewater because treatment facilities are ill-equipped to remove these substances. Medications not fully absorbed by the human body are excreted and end up in sewage systems, while improper disposal of medications — down the sink, flushed or even thrown in the bin — contributes further.
Researchers at Dartmouth Medical School, United States, found that the constant release of pharmaceutical waste into water bodies was impacting aquatic life: Estrogen-caused vitellogenesis in male Japanese medaka fish, caused more male fish to convert into female fish and led to an increased mortality rate. Further research found an increased prevalence of breast and testicular cancer in areas with drinking water contaminated with pharmaceutical waste.
Wastewater treatment plants are not designed to remove every environmental pollutant possible, but new treatment processes could be introduced to combat the impact of pharmaceuticals. Reducing contamination at the source is one option and programs for responsible, proper medication disposal and public education should reduce the volume of pharmaceuticals entering the waterways in the first place. Surveys conducted by UC Santa Barbara suggest a willingness among the American public to support these initiatives, but there remains the need to remove those drugs that have already made their way into the water system.
Fortunately, there are methods available.
Anaerobic wastewater treatment is deemed to be the most cost-efficient technology for treating organically polluted effluents from industrial use, according to researchers from Kalinga Institute of Industrial Technology, India. Biodegradable material is digested into biogas and “sludge,” which can then be removed.
Advanced oxidation processes use ozone to remove antibiotics, acetaminophen (paracetamol) and hormones from wastewater. These processes use photocatalysis to remove penicillin and can even be solar-powered. Electrochemical conversion removal techniques can also modify pharmaceutical particles into biodegradable compounds.
The World Atlas of Desertification estimates that only 18 percent of cultivated lands are irrigated. But these irrigated lands produce 40 percent of all food.
Another way to remove antibiotics involves composite membranes made from 2D nanomaterials and MXenes. MXenes are a family of 2D materials that can be used as sheets and stacked on top of each other into flexible and stable films. Researchers from Khalifa University designed membranes to tackle the removal of pharmaceuticals from hospital wastewaters.
“The excessive release of antibiotics has been alarmingly correlated to the problem of ‘superbugs,’” Shadi Hasan, lead author of the study, tells KUST Review.
Algal-based treatment technologies are also on the rise. Microalgae are already used to remove excess nutrients from wastewater, such as nitrogen, phosphorus and carbon, as a natural disinfection process. The algal biomass absorbs the nutrients and can then be harvested and used as a bio-fertilizer. Studies have shown algae can absorb lipophilic pharmaceuticals, which could make them a viable alternative for removing certain drugs like artificial hormones from wastewater.
Finally, nanotechnology could have great potential in adsorbing contaminants from wastewater. Silver and titanium dioxide nanoparticles have been applied for disinfection and decontamination of organic compounds, while iron nanoparticles can be used to remove heavy metals. Nano-based technologies could make industrial wastewater treatment more efficient, cost-effective and eco-friendly.
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