Water Pollution: Understanding The Ph Impact

Water pollution is a pressing issue that affects billions of people worldwide. One of the most devastating side effects of pollution is increased acidity in rain and groundwater, which has far-reaching implications for our environment. The pH scale, ranging from 0 to 14, measures the acidity or alkalinity of a liquid, with 7 being neutral. While natural alkaline substances in the soil can reduce the impact of pollution, the result is often a much more acidic environment than normal. This heightened acidity has detrimental effects on plants, animals, and aquatic life, and can even corrode water pipes and water-using appliances.

Acidic compounds in the soil

Soil acidity is a major problem affecting many soils around the world. It is caused by a buildup of hydrogen cations, which reduces the soil pH. This can happen when a proton donor is added to the soil, such as nitric acid, sulfuric acid, carbonic acid, or aluminium sulfate. Acidic soils can also be caused by heavy rainfall, which washes away beneficial elements like calcium and magnesium, and the natural breakdown of organic matter.

The pH scale measures the acidity or alkalinity of a liquid, with 7 being neutral, anything below 7 acidic, and anything above 7 alkaline. Soil is considered acidic when it has a pH level of less than 6.5, and very acidic when the pH is 5.5. Acidic soils can have negative effects on plant health, making nutrients less available to roots and increasing the impact of toxic elements like aluminium and manganese.

Soil acidification can be accelerated by certain human activities, such as agriculture and pollution, which contribute to acid rain. Acid rain is caused by the presence of certain gases in the atmosphere, including sulfur dioxide and nitrogen oxides, which can come from natural sources like lightning and volcanic eruptions, or from human activities such as the combustion of fossil fuels and motor vehicle exhaust. When acidic rainwater flows through the soil, it washes away basic cations like calcium, allowing aluminium and proton levels to increase.

In addition to acid rain, other human activities that can contribute to soil acidification include the use of chemical fertilizers, particularly those that are sulfur-based or ammonium-based nitrogen fertilizers.

The effects of acidic soils can be mitigated through the use of lime, organic amendments (such as straw and manure), and biochar application.

Acid rain

The effects of acid rain are far-reaching and detrimental. It can harm plants, aquatic animals, and infrastructure. In ecosystems, acid rain reduces tree bark durability, making trees more susceptible to environmental stressors like drought and pests. It also strips essential nutrients from the soil, such as calcium and magnesium, which are crucial for plant growth. Acid rain has been shown to negatively impact fish populations, with some species like the brook trout disappearing from certain lakes, streams, and creeks.

Additionally, acid rain causes corrosion of steel structures like bridges and damage to stone buildings and statues. It also poses risks to human health, causing respiratory issues and other indirect health effects through contaminated food and water sources.

The adverse consequences of acid rain have led to efforts by governments in Europe and North America to reduce sulfur dioxide and nitrogen oxide emissions through air pollution regulations. These efforts have yielded positive results, with acid rain levels dropping significantly since the 1970s.

Industrial waste

In many cases, industrial wastewater is properly cleaned by industrial wastewater recycling systems and is sometimes reused or disposed of in an environmentally friendly way. However, in some areas of the world, it is discharged untreated into nearby public waters. This discharge of residual pollution into public waters has serious consequences. Many of the hazardous substances from industry are difficult to biodegrade and therefore accumulate in water sediments. The consequence of this industrial wastewater pollution is that fish, crustaceans and other creatures become ill, and some die.

Through cracks in the ground, the polluted water from rivers and the contaminants from the water sediments get into the groundwater and thus into the drinking water. Industrial waste and water pollution can contain many different substances, and the composition of industrial wastewater depends on its origin from production. Often there is a mix of toxic substances.

The optimal pH of wastewater refers to the pH range at which the biological, chemical, and physical processes in a wastewater treatment system are most efficient. The optimal pH for wastewater can vary depending on the specific treatment process and the characteristics of the wastewater. For example, in biological wastewater treatment processes, such as activated sludge, aerobic digestion, and anaerobic digestion, the optimal pH range for most biological treatment processes is typically around neutral to slightly alkaline, between pH 6.5 and 8.5. At this pH range, microbial activity is maximized, leading to efficient organic matter removal and pollutant degradation.

In chemical precipitation and coagulation, the effectiveness of these processes is influenced by the pH of the wastewater. The optimal pH range for these processes may vary depending on the specific chemicals used, but is generally in the slightly acidic to neutral range, typically around pH 6 to 8. Adjusting the pH to the optimal range helps facilitate the formation of insoluble precipitates that can be easily separated from the water.

In nitrification and denitrification, the optimal pH for each of these processes is different. Nitrification is carried out by aerobic bacteria that convert ammonia (NH₃) to nitrite (NO₂-) and then to nitrate (NO₃-). The optimal pH range for nitrification is typically between 7.5 and 8.5. Denitrification is the process where anaerobic bacteria convert nitrate (NO₃-) to nitrogen gas (N₂) in the absence of oxygen. The optimal pH range for denitrification is generally lower than that for nitrification, typically between 6.5 and 7.5.

In hydrolysis and acidogenesis, which are initial stages of anaerobic digestion, the optimal pH range is typically around neutral to slightly acidic, between pH 6.5 and 7.5. These stages help break down complex organic compounds into simpler compounds that can be further converted to biogas.

Overall, the pH of wastewater affects the environment when discharged into receiving water bodies. Large variations in pH can be harmful to aquatic life and can disrupt the ecological balance. Therefore, it is essential to adjust the pH of treated wastewater to be within the acceptable range before discharge to minimize environmental impacts.

Sewage treatment

The pH of water is a critical measurement of water quality. It is a measure of how acidic or basic water is, and it can be affected by chemicals in the water. The pH scale ranges from 0 to 14, with 7 being neutral. A pH below 7 indicates acidity, while a pH above 7 indicates a base.

Preliminary Treatment

This step involves screening the sewage water to remove large objects such as rags, sticks, and debris. This step does not directly affect the pH but is necessary to prevent damage to equipment in subsequent treatment stages.

Primary Treatment

In this stage, the sewage undergoes sedimentation, where solid organic matter is allowed to settle at the bottom as primary sludge, while grease and oil float to the surface as scum. The primary goal of this step is to remove suspended solids and some organic matter, which can indirectly affect the pH by reducing the amount of material available for biological treatment.

Secondary Treatment

Also known as biological treatment, this stage uses microorganisms to break down organic matter in the sewage. The pH is carefully controlled in this step as it can impact the effectiveness of the treatment. For example, bacteria used to digest organic material will die if the pH is too high or too low. Additionally, chlorine-based disinfectants used in this stage are less effective under basic conditions.

Tertiary Treatment

This advanced treatment stage is designed to remove any remaining impurities and polish the treated sewage before it is discharged back into the environment. Processes such as filtration, disinfection, and pH adjustment are commonly used in this stage. The specific processes employed will depend on the intended use of the treated water and the required quality standards.

Discharge

After treatment, the effluent is discharged into receiving waterways. It is important to monitor the pH of the treated sewage at this stage to ensure it falls within acceptable ranges. Extreme pH values can harm aquatic ecosystems and waterways. Treated sewage that is too acidic can corrode pipes, leach toxic metals, and harm aquatic life. On the other hand, effluent that is too basic can increase water hardness and cause scale build-up and mineral deposition in pipes.

In conclusion, sewage treatment plays a crucial role in controlling the pH of wastewater and ensuring that it meets environmental standards before being discharged back into natural water bodies. By carefully adjusting and monitoring the pH at various stages of the treatment process, we can minimize the impact of sewage on the environment and protect the delicate balance of aquatic ecosystems.

Heavy metals

Sources of Heavy Metal Pollution

Natural Sources

Natural sources of heavy metal pollution include leaching, weathering, and volcanic eruptions. During weathering, rocks, soil, and minerals are broken down by interactions with elements such as oxygen and water, living organisms, and the atmosphere. This process can release heavy metals into water bodies. Volcanic eruptions can also release heavy metals into the environment, which can then contaminate water sources.

Anthropogenic Sources

Anthropogenic sources of heavy metal pollution are primarily driven by human activities and include industrial waste, agricultural practices, and domestic waste. Industrial activities, such as coal washery, steel production, food processing, plastic processing, and metallic work, often release untreated or partially treated effluents containing heavy metals into water bodies. Agricultural activities, including the use of pesticides, fertilizers, and herbicides, can also contribute to heavy metal contamination in water. Domestic waste, which includes organic matter, microorganisms, salts, chlorides, nutrients, detergents, oils, grease, and heavy metals, can also find its way into water bodies through improper waste disposal and wastewater discharge.

Effects of Heavy Metal Pollution on Water pH

Health Risks Associated with Heavy Metal Pollution

The presence of heavy metals in water poses significant health risks to humans. Consumption of water contaminated with heavy metals has been linked to various health issues, including liver failure, kidney damage, gastric and skin cancer, mental disorders, and harmful effects on the reproductive system. Additionally, heavy metals can cause carcinogenic effects and respiratory disorders. For instance, exposure to cadmium has been associated with reproductive, cardiovascular, pulmonary, and gastrointestinal disorders.

Removal and Remediation of Heavy Metals from Water

Several methods are available for the removal of heavy metals from water, including physicochemical and biological approaches. Physicochemical methods, such as reverse osmosis, chemical precipitation, and membrane filtration, are commonly used but tend to be costly and generate large amounts of secondary pollutants. Biological methods, such as biosorption, bioaccumulation, bioreduction, phytoremediation, and mycoremediation, are considered more cost-effective and eco-friendly. These techniques utilise living organisms and materials from the natural world, such as fungi, algae, bacteria, plant biomass, and agricultural residue, to remove heavy metals from water.

Frequently asked questions