Water Treatment Processes

Environmental Engineering

What are the steps to treat surface water?

Screening and Grit Removal

Primary Sedimentation

Rapid Mixing and Coagulation

Flocculation

Secondary Sedimentation

Filtration

Sludge Processing

Disinfection

Screening and Grit Removal

The initial steps in water treatment that involve the removal of large debris and grit from surface water to prevent damage to equipment and enhance further treatment processes.

Primary Sedimentation

The process where suspended solids settle to the bottom of a treatment basin, allowing clearer water to be collected from the top for further treatment.

Rapid Mixing and Coagulation

A process where chemicals (coagulants) are added to water to promote the aggregation of particles into larger clumps (flocs), followed by rapid mixing to ensure thorough dispersion.

Flocculation

The gentle mixing process following coagulation, where flocs are allowed to grow larger and settle more effectively before sedimentation.

Secondary Sedimentation

The process that follows biological treatment, where remaining suspended solids settle out of the water after secondary treatment, ensuring clearer effluent for further purification or discharge.

Filtration

The process of passing water through porous materials to remove remaining particles, flocs, and microorganisms, producing clearer and cleaner water for safe use or discharge.

Sludge Processing

The treatment of accumulated sludge from wastewater processes to reduce its volume and make it suitable for disposal or further processing.

Disinfection

The final step in water treatment that uses chemical agents or physical methods, such as chlorine or ultraviolet light, to eliminate pathogens and ensure water safety for consumption and discharge.

What are the steps for groundwater treatment?

Aeration

Flocculation & Precipitation

Sedimentation

Recarbonation

Filtration, disinfection, solid processing

Aeration

is the process of introducing air into water to enhance oxygen transfer and help break down organic matter.

Flocculation & Precipitation in Groundwater Treatment

Gentle mixing of water with coagulants to make flocs

Precipitates: process where hardness causing ions are converted to precipitates that can be removed

Sedimentation in Groundwater Treatment

Removes flocs and precipitates to settle at bottom of a treatment vessel, allowing clearer water to be collected from the top.

Recarbonation

is the process of adding carbon dioxide to water after the removal of hardness and alkalinity, which helps to stabilize the pH and prevent corrosion.

Filtration, disinfection, solid processing

in groundwater treatment involves removing remaining impurities from water, ensuring it is safe for consumption.

What are colloids?

Very small particles stable in suspension and do not easily settle

They contribute to turbidity and cloudiness

Needs coag and flocc to be removed because of their negative surface charges

Inorganic Particles vs. Organic Particles

Inorganic: hydrophobic

Organic: hydrophilic

Both have negative electric charges

What are disinfection by products?

Unintended chemicals formed during the disinfection process, often resulting from the reaction of disinfectants with natural organic matter in water. They can have health implications and are regulated in drinking water standards.

What is Neutralization Theory?

Coagulants neutralize the particle charge (negative charge) in order to reverse repulsion

Alum most common

What is sweep floc theory?

A mechanism by which larger flocs capture smaller particles in the water, enhancing sedimentation and removal efficiency during the treatment process.

Particle Efficiency Factor

Number of collisions between particles that result in aggregation