A wastewater treatment plant based on activated sludge with biological phosphate and nitrogen removal via pre-denitrification. The influent flow (dwf) is 30,000 m3/day and the influent BOD concentration is
300 mg BOD/l. The suspended solid concentration in the influent is 150 mg/l of which 40% is removed in the primary clarifier. The sludge recycle flow ratio (fr) is 0.5, the sludge yield (Y) is 0.6 kgX/kgBODremoved and the SVI is 130 mL/g.
The treatment plant consists of different process units, namely:
Final clarifier
Screen
Aerobic tank
Primary sedimentation
Anoxic tank
Grit chamber
Anaerobic tank
Sludge dewatering
After dewatering the sludge will be directly transported to the sludge incineration plant.
What is correct for the aerobic granules of a Nereda system.
1)Nitrification takes place inside the granule
2)Denitrification takes place inside the granule
3)Due to reduction of oxygen in the outer layer, anoxic conditions will exist inside the granule
4)Due to diffusion limitation the substrate can only reach the outer layer of the granule
5)Aerobic granules make settling tanks superfluous
6)Screening is not needed due to the characteristics of the aerobic granular sludge
The waste sludge of the Nereda installation is added to the conventional wastewater treatment plant, which will lead to a decreased SVI of the activated sludge plant. What is the main advantage of a lower SVI?
1)The maximum sludge concentration in the return flow will increase, reducing biomass storage in the final clarifier during rwf, decreasing the chance for biomass wash out.
2)The biomass concentration in the aeration tank can increase, which could lead to higher conversion capacity.
3)The size of the final clarifier can be reduced due to the increased settling velocity of the aerobic granules in the sludge.
4)The oxygenation capacity will increase due to a higher alpha factor of the sludge water mixture.
please help
i personally got this one wrong.. if you need other answer i may help :)
2C1 2C2 2D1 2D3 please someone tell the answer i really need it!!
thank you :)
2D1:
4
1:10
higher than 0.03 m/s
What is correct for the aerobic granules of a Nereda system:
Denitrification takes place inside the granule
Due to reduction of oxygen in the outer layer, anoxic conditions will exist inside the granule
Aerobic granules make settling tanks superfluous
What is the main advantage of a lower SVI?
The maximum sludge concentration in the return flow will increase, reducing biomass storage in the final clarifier during rwf, decreasing the chance for biomass wash out.
The biomass concentration in the aeration tank can increase, which could lead to higher conversion capacity.
To answer these questions, we need to understand the processes involved in wastewater treatment and the characteristics of the different process units.
1) What is correct for the aerobic granules of a Nereda system?
The Nereda system is a type of wastewater treatment system that relies on aerobic granular sludge. Aerobic granules are dense aggregates of microorganisms that perform various biological processes. Based on the given information, we can determine the correct statements:
- 1) Nitrification takes place inside the granule: Correct. Nitrification is the process of converting ammonia to nitrate, and it occurs in the presence of oxygen. In the aerobic granules, oxygen is available, allowing for nitrification to occur within the granule.
- 2) Denitrification takes place inside the granule: Incorrect. Denitrification is the process of converting nitrate to nitrogen gas, and it occurs under anoxic (low oxygen) conditions. However, the given system does not mention anoxic conditions within the granules.
- 3) Due to reduction of oxygen in the outer layer, anoxic conditions will exist inside the granule: Incorrect. The given information does not specify the reduction of oxygen in the outer layer of the granule, nor does it mention anoxic conditions within the granules.
- 4) Due to diffusion limitation, the substrate can only reach the outer layer of the granule: Incorrect. Diffusion limitation refers to the limitation in the transport of substrates (such as organic matter) towards the interior of the granule. However, the given system does not mention diffusion limitation within the granules.
- 5) Aerobic granules make settling tanks superfluous: Incorrect. While aerobic granules can enhance settling properties, making the sedimentation process more efficient, settling tanks (e.g., final clarifiers) are still required in a complete wastewater treatment plant.
- 6) Screening is not needed due to the characteristics of the aerobic granular sludge: Incorrect. Screening is an essential process in wastewater treatment plants. It involves the removal of large solids, such as debris, from the influent wastewater before it enters the treatment process. The characteristics of aerobic granular sludge do not eliminate the need for screening.
Based on the given options, only option 1 is correct: Nitrification takes place inside the granule.
2) What is the main advantage of a lower SVI (Sludge Volume Index)?
The SVI is a measure of sludge settling characteristics, indicating how well the sludge settles in the final clarifier. A lower SVI value indicates better settling properties. The main advantage of a lower SVI is:
- 1) The maximum sludge concentration in the return flow will increase, reducing biomass storage in the final clarifier during rwf, decreasing the chance for biomass washout: Correct. When the SVI is lower, it means that the sludge settles more efficiently, reducing the risk of excess biomass being carried over with the treated effluent in the final clarifier. This helps to maintain a higher concentration of biomass in the treatment system and minimizes the loss of microorganisms through washout.
- 2) The biomass concentration in the aeration tank can increase, which could lead to higher conversion capacity: Incorrect. While a lower SVI may allow for higher biomass concentration in the aeration tank, it does not directly impact the conversion capacity of the microorganisms.
- 3) The size of the final clarifier can be reduced due to the increased settling velocity of the aerobic granules in the sludge: Incorrect. A lower SVI indicates better settling, but it does not necessarily mean that the size of the final clarifier can be reduced. The design of the clarifier depends on various factors, including the design criteria, loading rates, and effluent quality requirements.
- 4) The oxygenation capacity will increase due to a higher alpha factor of the sludge-water mixture: Incorrect. The oxygenation capacity in a wastewater treatment plant is mainly determined by the aeration system and the design of the aeration tank. The SVI, while related to settling characteristics, does not directly affect the oxygenation capacity.
Based on the given options, only option 1 is correct: The maximum sludge concentration in the return flow will increase, reducing biomass storage in the final clarifier during rwf, decreasing the chance for biomass washout.