Suspended Matter: Understanding Water Pollution's Hidden Danger

Suspended matter water pollution refers to small solid particles that remain in suspension in water, causing it to become cloudy or muddy. These particles can include soil, agricultural runoff, and organic or inorganic matter, which settle and form a thick silt at the bottom, harming marine life. As an indicator of water quality, the presence of suspended solids can impact the strength of sewage and wastewater. The removal of these solids is crucial for water treatment and can be achieved through sedimentation and filtration processes.

Suspended Matter Water Pollution

Particulate matter

Suspended matter in water refers to small solid particles that remain in water without dissolving due to their large molecular size. This particulate matter is also known as suspended solids and can be naturally occurring or caused by human activity.

Natural Sources of Particulate Matter

Some suspended matter occurs naturally in water bodies, including fine plant debris, plankton, and minerals. These particles contribute to the turbidity, or cloudiness, of the water, which can impact the health of aquatic ecosystems. For example, high levels of suspended sediment can block sunlight from reaching bottom-dwelling plants, leading to their eventual death. This loss of vegetation can have cascading effects on the ecosystem, as these plants provide habitats for aquatic organisms, produce oxygen, and help trap sediment.

Human-Induced Particulate Matter

Human activities also introduce particulate matter into water systems. Agricultural runoff, urban areas, and construction sites are common sources of soil erosion, which can result in muddy or cloudy water. This type of water pollution is known as nonpoint source pollution, as it originates from diffuse sources rather than a single, identifiable point.

Additionally, human-induced particulate matter can include organic and inorganic matter, as well as toxic chemicals. Biodegradable substances, for example, can increase the number of anaerobic microorganisms in the water, creating a harmful environment for aquatic life.

Impact of Particulate Matter on Water Quality

Suspended solids are an important indicator of water quality. The smaller the particle size, the higher the potential pollutant load it can carry. These pollutants and pathogens can have detrimental effects on aquatic life, affecting their development and survival. Therefore, removing suspended solids through sedimentation and filtration processes is crucial for maintaining healthy water systems and ensuring water is safe for human consumption.

Sewage treatment

Suspended matter in water refers to small solid particles that remain in water as a colloid or due to the motion of the water. These particles can cause water pollution and are harmful to marine life. Sewage treatment is a crucial process in addressing water pollution caused by suspended solids. Here is an overview of the sewage treatment process:

Primary Treatment

The primary treatment of wastewater is a critical step in removing suspended solids. This stage focuses on eliminating materials that float or settle due to gravity, such as floating debris and suspended solids. Primary sedimentation tanks play a vital role in this process, removing a significant portion of total suspended solids (TSS) and other contaminants. The efficiency of these tanks depends on various factors, including detention period, wastewater characteristics, and particle size. Well-executed primary treatment can remove up to 60% or more of suspended solids, improving water quality and reducing contamination risks.

Secondary Treatment

The secondary treatment of wastewater is pivotal in addressing the biological remediation of soluble organic matter that escapes primary treatment. This stage refines water quality by eliminating additional contaminants such as biochemical oxygen demand (BOD), chemical oxygen demand, and ammonia nitrogen. Advanced technologies, such as coagulation-flocculation processes and various types of filters, are employed in this stage to target colloidal particles and very fine suspended solids.

Tertiary Treatment

After primary and secondary treatments, tertiary or advanced treatment may be necessary to ensure the water is safe for discharge or reuse. This stage involves disinfection to neutralize any remaining pathogens associated with suspended solids. Cloth filtration systems, for example, can effectively remove suspended solids, ensuring the water is safe for drinking.

Sustainable Methods

Some sustainable methods for sewage treatment include the oxidation pond method, which uses sunlight, algae, and aerobic bacteria to treat small sewage flows. While slower, this method aligns with sustainability goals by minimizing energy consumption. Moving bed biofilm reactors are another sustainable approach, utilizing flexible media carriers to develop layers of biofilms that efficiently degrade organic contaminants.

Impact on marine life

Marine life is incredibly vulnerable to the effects of water pollution. The ocean is an essential part of the global environment, influencing climate and weather and providing millions of different forms of life with a home. Water pollution can cause direct harm to marine life, as well as damage their environments, which in turn has indirect consequences.

One of the most pressing issues is the introduction of contaminants that marine life is not evolved to deal with. For example, heavy metals, oil spills, and pesticides can directly harm aquatic organisms. Fish can ingest these toxic substances, leading to deformities like gill damage, fin and tail rot, reproductive problems, and even death. Pesticides can also be absorbed into marine food webs, causing mutations and diseases that are harmful to humans and the entire food web. Toxic metals can cause changes to tissue matter, biochemistry, behaviour, and suppression of growth in marine life.

Another issue is the impact of pollution on the growth of fungus, bacteria, and algae. These can overtake and impede the growth of naturally occurring plants that marine life depends on to survive. Algal blooms, or red tides, have been linked to increasing ocean temperatures. Some species of cyanobacteria can produce excessive amounts of biomass that prevent light from getting below the ocean surface. As these organisms die and decompose, oxygen levels decrease, creating 'dead zones' where fish and other life can suffocate.

Marine debris, such as plastic pollution, is another significant threat to marine life. Plastic pollution can be harmful to marine life in several ways. Animals can become tangled and injured in plastic debris, and some may even mistake plastic for food and eat it. Small organisms, such as plankton, can ingest microplastics, and when they are eaten by larger animals, the toxic chemicals become part of their tissues. In this way, microplastics can migrate up the food chain, eventually reaching humans.

Water pollution can also have broader ecological consequences. Submerged aquatic vegetation (SAV) is an important component of aquatic ecosystems, providing habitats, producing oxygen, and trapping sediment. However, when soil, or suspended sediment, blocks out sunlight, these plants can die, leading to hypoxic conditions that are uninhabitable for aquatic organisms. Climate change further exacerbates these issues, with rising water temperatures, acidification, and low oxygen levels creating extreme marine events and disrupting marine ecosystems.

Removal methods

Suspended solids refer to small solid particles that remain in suspension in water as a colloid or due to the motion of the water. These solids can range from algae and plankton to bacteria, sand, and other debris. The removal of suspended solids is essential for producing clean and safe drinking water.

Sedimentation

Sedimentation is the process of allowing particulates to settle out of the water. This is done by letting the water stand in a large tank or basin, allowing the particles to settle at the bottom. The rate of settling is influenced by the size and shape of the particulates, their density, and the viscosity of the water. To speed up the process, a coagulant can be added to bind the solids together, causing them to clump and settle faster.

Filtration

After sedimentation, the water can be filtered using a fine mesh or physical filter to remove the remaining suspended particles. This is typically done using a series of filters, including rapid sand filters, pressure filters, and cartridge filters. Each type of filter is designed to remove particulates of different sizes. For example, rapid sand filters use sand particles as a filter medium to capture small particulates.

Screening

Screening is a pre-treatment step that involves using screens or filters to remove large particulates from the water before the sedimentation process. This step is particularly useful for industrial wastes containing larger suspended solids of variable sizes, such as those from canneries, pulp and paper mills, or poultry processing plants.

Disinfection

Even after removing most suspended solids, disinfection is necessary to ensure that any remaining pathogens are rendered ineffective. This can be achieved through methods like solar water disinfection, especially in cases where simple cloth filters are used for filtration.

It is important to note that certain pollutants, such as arsenic contamination in groundwater, are soluble and cannot be removed through the above-mentioned methods.

Natural vs human-caused

Suspended matter in water refers to small solid particles that remain in suspension in water as a colloid or due to the motion of the water. These particles are often referred to as suspended solids or particulate matter. Suspended solids can be organic materials such as algae, or inorganic materials like silt and sediment.

Natural Causes

Suspended solids in water bodies can occur naturally due to factors such as organic materials (including algae), inorganic materials (such as silt and sediment), and natural processes like erosion and resuspension from seasonal water flow. The local geology, including normal flow rates, soil type, land structure, and vegetation, influences the natural turbidity levels of a water body. Turbidity refers to the measurement of water clarity determined by the amount of light scattered by suspended solids and dissolved coloured material.

Human Causes

While suspended solids in water are often due to natural causes, excess concentrations are frequently attributed to human activities, whether directly or indirectly. Human-caused pollution can contribute to both organic and inorganic suspended solids in water bodies. For example, inorganic suspended solids can result from industrial activities, such as the chemical plant near Rheinfelden, which released hexachlorobenzene (HCB) into the Rhine River. Lead (Pb) in the Rhine also originated from human activities, specifically exhaust fumes from cars.

Human alterations to the surrounding land, such as agriculture, construction, or other soil-disturbing activities, can accelerate erosion and runoff, increasing turbidity and the presence of suspended solids. Additionally, pollution from large garbage to microplastics, flecks of metal, asphalt, and chemical dyes can contribute to the presence of suspended solids in water.

It is important to distinguish between natural turbidity caused by suspended matter and true pollution, which occurs when pollutants adsorb to suspended particles. These pollutants can enter water bodies through various pathways, including runoff, leaching, erosion, and dredging, ultimately impacting the quality of the water and the health of aquatic ecosystems.

Frequently asked questions