Water Quality and Global Health
Around 70% of the Earth’s surface is covered by water, and the quality of this water is of paramount importance. Unclean water can lead to a myriad of health problems and can severely damage various bodily functions. The consequences of consuming contaminated water are grave and should not be underestimated.
The Ongoing Challenge of Water Pollution
In today’s world, the improvement of municipal water supplies often lags behind the pace of water source pollution. Human efforts to manage and treat water struggle to keep up with the speed of water contamination. Furthermore, our understanding of waterborne viruses often falls short of the rapid mutations these pathogens can undergo. Additionally, the degradation of organic substances in water cannot match the rate at which new organic compounds are synthesized. All these factors exacerbate the challenge of maintaining water quality, particularly in the face of modern economic development that often disrupts the planet’s ecosystems.
The Complex Process of Water Pollution
Water pollution originates from various sources, demonstrating its diverse nature. Pollution sources can include industrial wastewater discharges, agricultural runoff carrying pesticides and fertilizers, urban and rural sewage outlets, improper medical waste disposal, accumulation of waste materials, and deposition of pollutants from the atmosphere into water bodies. These sources introduce a wide range of harmful substances into water, resulting in the deterioration of water quality.
Factors Influencing Water Quality in Municipal Supplies
Primary Influence: Raw Water Quality: The primary determinant of water quality is the raw water source. Even though raw water may meet hygiene standards, it often contains suspended particles, residual chlorine, dissolved chlorine, free carbon dioxide, carbonate ions, nitrate ions, and iron and manganese oxidation products formed by chlorine oxidation of iron and manganese in the water. Accumulation of these substances on the inner walls of pipelines can increase turbidity, color, iron content, and manganese content in the network water. Furthermore, the increasing discharge of industrial wastewater has led to the direct contamination of surface water sources, impacting water quality. While groundwater sources tend to be less affected, excessive use of chemical fertilizers and pesticides in recent years has introduced contaminants into groundwater, affecting its quality.
Influence of Pipeline Materials: The choice of pipeline materials can affect water quality differently. Metal pipelines are susceptible to corrosion, primarily forming iron-based scale due to water corrosion. With prolonged usage, the scale layer becomes thicker, increasing pipeline resistance. Microorganisms and organic matter can adhere to the inner pipeline walls, promoting the growth of anaerobic bacteria and resulting in bacterial contamination exceeding standards. In cases where the inner walls of cement pipes are not smooth, similar issues may occur.
Impact of Pipeline Ancillary Facilities and Design: Proper operation of a water distribution network necessitates the installation of control valves, blowdown valves, and fire hydrants, among other ancillary facilities. These facilities, located underground or exposed to the elements, are often vulnerable to erosion by rainwater or other pollutants. When network pressure is lost, nearby wastewater can be drawn into the network, causing secondary pollution.
Pipeline Flow Rate and Unstable Network Pressure: Low water flow rates in pipelines or oversized pipes with limited users can lead to prolonged water retention times in the pipes. This can promote the oxidation and sedimentation of iron and manganese, exacerbating water quality issues. During peak water usage, especially in high-rise buildings, low pressure can lead to water backflow, potentially contaminating the network. Solar water heaters, due to their direct exposure to the atmosphere, can be prone to bacterial growth. When water from such heaters enters the network, it can impact water quality.
How to Detect Water Quality:
Visual Inspection: Fill a glass container with water and observe it against light for the presence of suspended particles. Let it sit for three hours and check for any sediment at the bottom, which indicates excessive suspended impurities.
Odor Assessment: Collect water from the tap in a glass container while keeping a distance from the faucet. Smell the water for any scent of chlorine or bleach. Detection of such odors suggests an excess of residual chlorine in tap water.
Taste Test: Drink a glass of hot tap water and evaluate whether it has a taste resembling chlorine or bleach. If such flavors are detected, it signifies an excess of chlorine, requiring terminal treatment with a water purifier.
Observation of Color Changes: Brew tea with tap water and observe whether the tea darkens overnight. If the tea darkens, it indicates excessive iron and manganese content in the tap water, necessitating the use of water purifiers with iron and manganese removal filters for terminal treatment.
Taste Assessment: Taste a glass of plain tap water and evaluate whether it has a bitter or astringent taste. Such tastes may indicate high water hardness.
Inspection of Household Water Heating Equipment: Examine the inner walls of household water heaters and kettles for the formation of yellow scale. If scale is present, it indicates high water hardness (excess calcium and magnesium salts). Early adoption of water softeners is recommended to prevent scale buildup, which can lead to poor heat exchange in water heaters and even burst pipes. Long-term consumption of hard water can contribute to various health problems, including kidney stones.
Aspects of Water Quality Testing:
| Detection Aspects | Parameters/Indicators |
|---|---|
| Physical Properties | |
| – Temperature | Degrees Celsius (℃) |
| – pH Value | Dimensionless |
| – Turbidity | Milligrams per Liter (mg/L) or Nephelometric Turbidity Units (NTU) |
| – Conductivity | Microsiemens per Centimeter (μS/cm) |
| Chemical Components | |
| – Dissolved Oxygen (DO) | Milligrams per Liter (mg/L) |
| – Ammonia Nitrogen (NH3-N) | Milligrams per Liter (mg/L) |
| – Total Nitrogen (TN) | Milligrams per Liter (mg/L) |
| – Total Phosphorus (TP) | Milligrams per Liter (mg/L) |
| – Iron (Fe) | Milligrams per Liter (mg/L) |
| – Manganese (Mn) | Milligrams per Liter (mg/L) |
| – Dissolved Organic Carbon (DOC) | Milligrams per Liter (mg/L) |
| – Heavy Metals (e.g., Lead, Cadmium, Mercury, etc.) | Milligrams per Liter (mg/L) |
| Microbial Contamination | |
| – Escherichia coli (E. coli) | Colony-Forming Units per 100 milliliters (CFU/100mL) |
| – Resistant Bacteria | Colony-Forming Units per 100 milliliters (CFU/100mL) |
| – Pathogenic Microorganisms (e.g., Salmonella, Vibrio cholerae, etc.) | Detected as Positive or Negative |
| Other Pollutants | |
| – Organic Pollutants (e.g., Pesticides, Volatile Organic Compounds) | Milligrams per Liter (mg/L) |
| – Radioactive Elements (e.g., Uranium, Strontium, Tritium, etc.) | Millibecquerels per Liter (mBq/L) |
| – Suspended Particulate Matter | Milligrams per Liter (mg/L) |
Only by working together can we ensure clean and healthy drinking water sources and maintain human health and the sustainable development of the earth’s ecology. Water is the source of life. Cherishing water resources and protecting water quality are crucial to our future.