CO2 pH Stabilization in Surface Water Coagulation
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Solution Overview
Problem
Surface water treatment plants face challenges in stabilizing the pH of pre-filtered water without increasing coagulant dosages, leading to inefficient coagulation and increased turbidity, which affects treatment costs and water quality.
Innovation Solution
Incorporating carbon dioxide into the raw surface water to adjust and stabilize the pH, combined with mechanical agitation or shear static mixing, reduces turbidity and allows for reduced coagulant dosages, thereby enhancing coagulation efficiency without lime softening.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If slaked lime is added to raise alkalinity and increase pH, then pH and alkalinity are improved, but turbidity increases to unacceptable values
Solution Approach 1:
Carbon dioxide is introduced as an intermediary substance to adjust pH and alkalinity indirectly. The CO2 reacts with water to form carbonic acid, which lowers pH and consumes alkalinity, providing a alternative mechanism to achieve pH control without the harmful turbidity increase caused by slaked lime addition
2Reliability
If coagulant dosage is increased to lower pH for enhanced coagulation, then coagulation efficiency is improved, but treatment cost increases
Solution Approach 1:
The invention changes the pH parameter through carbon dioxide addition rather than through coagulant dosage adjustment. This alternative parameter control method allows coagulation to proceed at optimal pH levels without requiring excessive coagulant doses, thereby maintaining coagulation efficiency while reducing chemical consumption and treatment costs
3Temperature
If coagulant dosage is increased to reach optimum pH for coagulation, then pH control is improved, but alkalinity is lowered
Solution Approach 1:
Carbon dioxide serves as an intermediary that adjusts pH through a different chemical pathway than coagulant addition. The CO2-based pH adjustment mechanism allows for better alkalinity management during the coagulation process, maintaining sufficient buffering capacity while achieving optimal pH conditions
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 method effectively stabilizes the pH of surface water, reduces coagulant usage by up to 65%, improves turbidity removal, and lowers treatment costs while maintaining optimal alkalinity and corrosion control in the water distribution system.
Implementation Method 1
dosing carbon dioxide into a volume of the raw surface water
Implementation Method 2
carbon dioxide...adjust and stabilize the pH
Implementation Method 3
applying mechanical agitation by positioning at least one impeller within a flow path of the raw surface water...and rotating the at least one impeller
Implementation Method 4
decreasing the turbidity of the raw surface water by further dissolving at least the coagulant
Implementation Method 5
applying a shear static mixer to the raw surface water
Implementation Method 6
feeding one or more coagulants into the volume of the raw surface water
Implementation Method 7
coagulation/flocculation...enhanced coagulation
Data Source
AI summary
In general, the present disclosure is directed to a method of pretreating raw surface water, including dosing carbon dioxide into a volume of the raw surface water, feeding one or more coagulants into the volume of the raw surface water; and decreasing the turbidity of the raw surface water by further dissolving at least the coagulant from said feeding.