西安建筑科技大学：《水资源利用与保护》参考资料_Wastewater as a resource_Advanced Treatment

Advanced Treatment in Activated Sludge Process

Advanced Treatment in Activated Sludge Process

Activated sludge process Aeration tank Secondary clarifier Influent Effluent Air supply Return sludge Excessive sludge

Activated sludge process Excessive sludge Effluent Secondary clarifier Influent Return sludge Aeration tank Air supply

Traditionally, activated sludge process is used to remove organic carbon(COD) from wastewaters(municipal and Industries In the process, microorganism in the sludge obtain their energy for cell synthesis (growth)through breaking down organic compounds into inorganic compounds( carbon dioxide) with oxygen as an electron acceptor Since 1970s, eutrophication in inland waters results in the world-wide concern about nutrient(N, P)removal from wastewaters. Traditional activated sludge processes are expanded to be applied in successfully removing n and p from water and wastewaters

Traditionally, activated sludge process is used to remove organic carbon (COD) from wastewaters (municipal and industries). In the process, microorganism in the sludge obtain their energy for cell synthesis (growth) through breaking down organic compounds into inorganic compounds ( carbon dioxide) with oxygen as an electron acceptor. Since 1970s, eutrophication in inland waters results in the world-wide concern about nutrient (N, P) removal from wastewaters. Traditional activated sludge processes are expanded to be applied in successfully removing N and P from water and wastewaters

Nitrogen Removal (Nitrification and Denitrification) Nitrification NH++3/20 Nitrisomenas No-+H0+2H+ NO,+1/20 Nitrobacter NO Denitrification NO3+ Org Denitrifiers +co+ho+oh Nitrification and denitrification can be achieved in activated sludge process and biofilm process. However, activated sludge process is the most widely used process in municipal and industrial wastewater treatment

Nitrogen Removal (Nitrification and Denitrification) Nitrification NH 4 + + 3/2O 2 NO 2 - + H 2O + 2H + NO 2 - + 1/2O 2 NO 3 - Denitrification NO 3 - + Org N 2 + CO 2 + H 2O + OH￾Nitrisomenas Nitrobacter Denitrifiers Nitrification and denitrification can be achieved in activated sludge process and biofilm process. However, activated sludge process is the most widely used process in municipal and industrial wastewater treatment

Single-stage Activated sludge Nitrogen Removal Process Mixed liquor return Effluent Influent Anoxic Aerobic Sludge return Excessive sludge

Single-stage Activated Sludge Nitrogen Removal Process Anoxic Aerobic Mixed liquor return Sludge return Excessive sludge Influent Effluent

Phosphorous Removal (BPR) Activated sludge processes with alternating anaerobic and aerobic conditions have been successfully used for enhanced biological phosphorous removal (EBPr) from wastewater. This anaerobic-aerobic alternation can be achieved either by spatial configuration of anaerobic and aerobic zones in series in continuous flow systems with sludge recycle or by temporal arrangement of anaerobic and aerobic periods in sequence batch reactors

Phosphorous Removal (EBPR ) Activated sludge processes with alternating anaerobic and aerobic conditions have been successfully used for enhanced biological phosphorous removal (EBPR) from wastewater. This anaerobic-aerobic alternation can be achieved either by spatial configuration of anaerobic and aerobic zones in series in continuous flow systems with sludge recycle or by temporal arrangement of anaerobic and aerobic periods in sequence batch reactors

Spatial Configuration of Anaerobic and Aerobic zones in Series in Continuous Flow Systems Anaerobic Aerobic Clarifier Inflow Outflow Sludge recycle Wasted sludge SBCOD PHA PO4-P Spatial configuration

Spatial Configuration of Anaerobic and Aerobic Zones in Series in Continuous Flow Systems Anaerobic Aerobic Clarifier Sludge recycle Inflow Wasted sludge Outflow SBCOD PHA Concentrations PO4-P Spatial configuration

Temporal Arrangement of Anaerobic and Aerobic in Sequence Batch Reactor Influent Fill Effluent Draw Anaerobic

Temporal Arrangement of Anaerobic and Aerobic in Sequence Batch Reactor Aerobic Anaerobic Settle Draw Fill Influent Effluent

Polyphosphate-accumulating bacteria(PAB) play an essential role for EBPr in the anaerobic-aerobic process To achieve high and stable phosphorous removal it is essential to maintain a high percentage of paB in the sludge of eBPR system

Polyphosphate-accumulating bacteria (PAB) play an essential role for EBPR in the anaerobic-aerobic process. To achieve high and stable phosphorous removal, it is essential to maintain a high percentage of PAB in the sludge of EBPR system

e The mechanism of proliferation of PAB can be described as follows It is ty pically observed in the anaerobic stage that the activated sludge releases P to the bulk solution with concomitant uptake of organic substrates In the subsequent aerobic stage, it takes up more P than has been released in the previous anaerobic stage. The P removed from the wastewater is accumulated in the cell as poly P. Poly phosphate is a high-energy compound and its hydrolysis can supply energy to various biochemical reactions in the cell. In the anaerobic stage, the hydrolysis of intracellular polyP enables PAB to obtain the energy they need to take up organic substrates Without electron acceptors (oxygen, No2 NO3), aerobic bacteria and denitrifying bacteria are unable to obtain the energy required for the utilization of organic substrates, and they are thus unable to compete with PAB. Therefore, the introduction of the anaerobic stage leads to the precedence of PAb and to a rise in phosphorus content of the sludge By withdrawing the phosphorus-rich sludge from the system as excess sludge, high phosphate removal efficiency can be achieved

The mechanism of proliferation of PAB can be described as follows. It is typically observed in the anaerobic stage that the activated sludge releases Pi to the bulk solution with concomitant uptake of organic substrates. In the subsequent aerobic stage, it takes up more Pi than has been released in the previous anaerobic stage. The Pi removed from the wastewater is accumulated in the cell as polyP. Polyphosphate is a high-energy compound and its hydrolysis can supply energy to various biochemical reactions in the cell. In the anaerobic stage, the hydrolysis of intracellular polyP enables PAB to obtain the energy they need to take up organic substrates. Without electron acceptors (oxygen, NO 2 -/NO 3 -), aerobic bacteria and denitrifying bacteria are unable to obtain the energy required for the utilization of organic substrates, and they are thus unable to compete with PAB. Therefore, the introduction of the anaerobic stage leads to the precedence of PAB and to a rise in phosphorus content of the sludge. By withdrawing the phosphorus-rich sludge from the system as excess sludge, high phosphate removal efficiency can be achieved