Wastewater Treatment: Processes and Technologies
Wastewater Treatment and Environmental Engineering
Environmental Engineering is the branch of engineering that focuses on protecting the environment from the harmful effects of human activity. It is mainly oriented towards managing and reducing the impact of issues such as waste.
Environmental Biotechnology applies modern biological processes to protect and restore environmental quality.
Coliform are indicator organisms found in the intestinal tract, indicating the presence of fecal contamination.
Wastewater Treatment aims to reduce organic and inorganic materials to levels that do not allow microbial growth.
BOD refers to the reduction of biological oxygen demand.
Primary Treatment
Primary treatment involves physical separations of large solids like sand and grease, sedimentation, and filtration, resulting in cleaner water.
Secondary Treatment
Secondary treatment includes:
- Anaerobic treatment for waters with high BOD demands.
- Aerobic treatment, which is more efficient and lower in cost. It involves the oxidation of biodegradable organic matter by bacteria to accelerate a natural process, preventing contaminants and oxygen depletion in the water.
Aerated lagoons are water reservoirs where water is oxygenated by submerged surface aerators or diffusers to generate bacterial oxidation. Solids are separated by decanting.
Activated sludge is stirred by pumps to keep it in constant contact with oxygen inside reinforced concrete pools. The organic matter of wastewater is degraded so that floc can then be decanted.
Tertiary Treatment
Tertiary treatment is more expensive and involves physicochemical processes like filtration and chlorination, similar to those used for potable water. It reduces inorganic nutrients, eliminates remaining organic matter from secondary treatment, disinfects, removes undesirable color and odor, and eliminates detergents, phosphates, and nitrates.
Water Purification
A treatment plant uses a sequence of processes to completely remove physical, chemical, and biological contaminants to increase water quality to acceptable levels.
Potabilization: Physical and Chemical Processes
Pre-treatment: Removes floating matter using thick bars, protects the pumping system, and extends the lifespan of equipment.
Coagulation-flocculation: Removes impurities and suspended material of small size.
Flocculation: Agitation allows water to induce coagulation, causing suspended particles to agglomerate into heavier flocs that can be decanted by gravity.
Sedimentation: A physical process that allows flocs to settle over time.
Filtration: Uses slow sand filters.
Disinfection: Reduces the potential harm of pathogens and microorganisms. Previous processes remove 90%, but additional disinfection is required to meet standards. Disinfectants must be toxic to microorganisms at the required concentrations, below the maximum limit for humans, have a high rate of kill, and be persistent to prevent regrowth.
Submarine Outfalls
Submarine outfalls deposit wastewater into the ocean to prevent harm to human health or significant pollution to aquatic ecosystems.
Wastewater collected through a network of collectors is carried to the main system, where it is driven by quantified units for the removal of solids. It then circulates through size reduction units before reaching the elevation equipment, where pumps drive the water to the submarine duct. The water is then transported and accelerated through a diffusion system with nozzles on the seabed.
The outfall process consists of three phases:
- Phase 1: Physical treatment
- Phase 2: Transport and evacuation
- Phase 3: Submarine treatment