Hybrid Activated Sludge and Ballasted Flocculation for Soluble BOD Removal
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Solution Overview
Problem
Ballasted flocculation systems are ineffective in removing soluble BOD, despite achieving high particulate BOD removal, leaving a need for a method to efficiently address this component of total BOD in water or wastewater treatment.
Innovation Solution
Combining an activated sludge system with a ballasted flocculation process, where activated sludge is mixed with wastewater upstream of the ballasted flocculation system to remove soluble BOD, while the ballasted flocculation process handles suspended solids and particulate contaminants.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If ballasted flocculation is used to clarify water or wastewater, then settling speed and overflow rate are improved, but soluble BOD removal is insufficient
Solution Approach 1:
The patent combines activated sludge process and ballasted flocculation process into a hybrid system. The activated sludge component provides biological degradation of soluble BOD, while the ballasted flocculation component provides rapid settling and removal of particulate matter. The mixed liquor from the activated sludge reactor is fed to the ballasted flocculation clarifier, which removes both biological floc and inert ballast particles, achieving simultaneous soluble BOD and suspended solids removal.
2Area of stationary object
If ballasted flocculation is used, then system footprint is reduced, but particulate and colloidal solids removal is limited
Solution Approach 1:
The hybrid system merges the compact design advantage of ballasted flocculation with the enhanced solids removal capability of activated sludge. The activated sludge process generates biological floc that effectively captures both particulate and colloidal solids through adsorption and enmeshment, while the ballasted flocculation component provides rapid settling. This combination maintains the small footprint benefit while significantly improving solids removal performance.
3Loss of time
If ballasted flocculation is used, then start-up and optimization times are shortened, but soluble BOD removal efficiency remains low
Solution Approach 1:
The activated sludge component is operated in advance to biologically degrade soluble BOD in the wastewater before the ballasted flocculation step. This preliminary biological treatment converts soluble organic matter into biological floc, which is then readily removable in the subsequent ballasted flocculation clarifier. This sequence allows the system to achieve high soluble BOD removal while maintaining the rapid start-up characteristics of ballasted flocculation.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This combination achieves significant removal of both soluble BOD and suspended solids, enhancing the overall treatment efficiency and capacity of water or wastewater treatment systems.
Implementation Method 1
soluble BOD in the second water or wastewater stream is removed by the activity of the activated sludge
Implementation Method 2
The faster settling of the ballasted floc allows for very high overflow rates in the clarifier or settling tank
Implementation Method 3
ballasted flocculation to clarify water or wastewater. A ballasted flocculation process allows for faster settling of the flocculated material that is formed in the process
Data Source
AI summary
A method and system for treating water or wastewater to remove both soluble BOD and suspended solids. The method entails directing first and second water or wastewater streams to a treatment system including an activated sludge system and a ballasted flocculation system. The first water or wastewater stream is directed to the activated sludge system which includes at least one reactor and a clarifier. The second water or wastewater stream is directed to a ballasted flocculation system. Mixed liquor or activated sludge is directed from the activated sludge system to a mixing chamber that is located upstream from the ballasted flocculation system. The water or wastewater of the second stream is mixed with the mixed liquor or activated sludge in the mixing chamber. The mixed liquor from the mixing chamber is directed to and through the ballasted flocculation system. In the end, the soluble BOD in the second water or wastewater stream is reduced and suspended solids in the water or wastewater are also reduced.