River VL 7 Flashcards
Wastewater Treatment Process
Wastewater treatment plants (WWTP) are essential for processing urban and industrial wastewater to protect environmental and human health. The treatment involves several stages: mechanical, biological, and advanced treatments to ensure that water discharged into the environment is clean and safe.
Primary Treatment: Mechanical Wastewater Treatment
1. Collection and Initial Screening: Wastewater is collected through a sewer network and initially passes through a grate to remove large debris such as paper, bottles, and branches.
2. Grit Channel: The flow of wastewater slows down in a wider channel, allowing sand and coarse materials to settle at the bottom.
3. Primary Clarification: Water is held for about two hours in large tanks where finer suspended particles settle. The resulting sludge is removed and sent to digestion towers.
Secondary Treatment: Biological Wastewater Treatment
1. Activated Sludge Tank: Oxygen is supplied to the wastewater to support bacteria that digest organic material. This process converts organic compounds into carbon dioxide, water, and other inorganic substances, forming activated sludge.
2. Secondary Settlement Tank: Activated sludge is separated from the treated water. Some of the sludge is recycled back
into the activated sludge tank, while excess sludge is processed further.
Tertiary Treatment: Nutrient Removal
1. Phosphate Elimination:
* Chemical Precipitation: Chemicals like lime (Kalk), iron chloride, or aluminum sulfate are added to bind
phosphates, which then settle out.
* Biological Phosphate Removal: Certain bacteria can store excess phosphate when stressed by alternating aerobic and anaerobic conditions, reducing the need for chemical additives.
2. Nitrogen Elimination:
* Nitrification: Ammonium in the wastewater is oxidized to nitrate [(NH4+) to nitrate (NO3-)] by bacteria inaerobic conditions.
* Denitrification: Nitrate is reduced to nitrogen gas in an anaerobic environment [red. of nitrate (NO3-) to
nitrogen gas (N2)] and released into the atmosphere.
* Or instead Anammox Process: This process allows for the direct conversion of ammonium to nitrogen gas under anaerobic conditions, saving energy and reducing costs. (Bacterium: Brocadia anammoxidans)
Advanced Treatment: Quaternary Treatment
* Absorption and Filtration: Non-biodegradable substances are removed using charcoal filters or other filtration methods.
* Additional Biological Treatment: Advanced treatment ponds may be used to further reduce suspended
solids, organic loads, and pathogens.
Sludge Treatment and Disposal
* Thickening: The water content of sludge is reduced from 98% to 96%, halving its volume.
* Digestion: Sludge is anaerobically digested in towers, producing biogas (mainly methane and CO2) which can be used to power the WWTP.
* Dehydration: The digested sludge is further dewatered using mechanical or natural methods. If free from heavy metals, it can be used as fertilizer or otherwise incinerated.
Shortly desribe the watewater treatment
Wastewater treatment is a multi-step process involving mechanical, biological, and advanced treatments to ensure that effluent meets environmental standards. Primary treatment removes large and coarse materials, secondary treatment focuses on biological degradation of organic matter, and tertiary treatment removes nutrients to prevent secondary pollution. Advanced treatments and sludge processing ensure that the final discharge and byproducts are safe for the environment.
What is the energy and carbon source of these processes:
photo-autotrophic, chemolitho-autotrophic, chemoorgano-heterotrophic?
- photo-autotrophic -> light & CO2
- chemolitho-autotrophic -> inorganic compounds & CO2
- chemoorgano-heterotrophic -> organic compounds & organic compounds
What is the use of constructed wetlands (reed beds)?
Constructed wetlands, or reed beds, are used in wastewater treatment plants for
* natural filtration,
* nutrient removal,
* pathogen reduction, and
* aesthetic improvement.
* They offer cost-effective and sustainable solutions by utilizing plant and microbial processes to clean wastewater.
* On the other hand, they require much space and maintenance.
