Wastewater treatment plant

24 important questions on Wastewater treatment plant

What occurs in the primary treatment of the WWTP?

Suspended solids, sands, oils, and fats are removed

What occurs in the secondary treatment of the WWTP?

Anoxic-aerobic biological treatment and membrane filtration is done

What happens in the aerobic zone?

Oxygen is supplied, promoting the nitrification process which tranforms ammonia into nitrate
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What happens in the anoxic section?

Partial denitrification that reduces nitrate to nitrogen gas

What is the biochemical oxygen demand (BOD)?

A parameter that represents the amount of dissolved oxygen that is consumed by bacteria that grow on organic material at a specific temperature and over a time period

How can carbon, nitrogen, phosphorous, and metals be removed from the wastewater?

Air is bubbled through the water so the microorganisms can remove these nutrients

What is the first sludge line, how is the microbial activity and what are the environmental conditions?

First sludge line has had no biological treatment yet, the microbial activity is low and the environmental conditions are mostly anaerobic or low oxygen.

What is the second sludge line, how is the microbial activity and what are the environmental conditions?

Second sludge line is formed by microbial growth. The microbial activity is very high and the environmental conditions are aerobic

What is the digester sludge, how is the microbial activity and what are the environmental conditions?

Digester sludge is a combination of primary + secondary sludge and, the microbial activity is moderate and the environmental conditions are strictly anaerobic.

What does munciple wastewater consist of?

Mainlywater and relatively small concentrations of suspended and dissolved organic and inorganic solids

How does primary settlement work?

The design of the tank allows particles to settle because of gravity

How does secondary settlement work?

Microorganisms break down dissolved and fine suspended organic matter.

How do the anoxic and aerated tanks contribute to nitrogen removal?

Oxygen is supplied for nitrification, the oxidation of ammonia which can then be removed in the anoxic tank

Why does the anaerobic tank not contribute to nitrogen removal?

It has no oxygen, so anaerobic digestion or biological phosphorus removal occurs, not nitrogen removal

Why is wastewater recirculated from the aerobic to the anoxic tank?

So the anoxic tank can use nitrate as an electron acceptor to turn into nitrogen gas

What does the screening and sedimentation steps remove from the wastewater?

In the screens sand, slit, grit, metal, etc and in the sedimentation floating solids

What happens in the aerobic reactors?

Mainly organic material composed of carbon will be removed

What processes happen in the aerobic reactors?

Oxidation of organic C to CO2, absorption, hydrolysis and cell synthesis

What is the Hydraulic Residence Time (HRT)?

The average time a given compound remains in a bioreactor

What is the Solids Residence Time (SRT)?

The average time microorganisms remain in the bioreactor

What are important parameters for aeration reactor design?

Temperature, pH and toxic compound production

What can be a problem in aerobic reactors?

Bulking and foaming and a low settling rate

What is an example of an anaerobic tank?

Upflow Anaerobic Sludge Blanket

What are the SRT and HRT like in the anaerobic tank example?

The SRT is longer and the HRT is shorter

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