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Struvite formation for enhanced dewaterability of digested wastewater sludge
Environmental Technology
|March 21, 2014
Summary
Controlled struvite formation improves digested sludge dewaterability, reducing transport volumes. Optimal results were achieved at pH 7.0 with stirring, enhancing orthophosphate removal.
Area of Science:
- Environmental Engineering
- Water Treatment Technologies
- Waste Management
Background:
- Controlled struvite formation in digested sludge offers improved dewaterability.
- This leads to reduced volumes of sludge requiring transportation.
- Understanding control parameters is key to optimizing this process.
Purpose of the Study:
- To investigate the effects of magnesium concentration and pH on digested sludge dewaterability.
- To correlate these parameters with the efficiency of struvite formation.
- To identify optimal conditions for enhanced sludge dewatering.
Main Methods:
- Laboratory experiments using a 20 L batch reactor with digested activated sludge.
- Carbon dioxide stripping and magnesium chloride addition to induce struvite formation.
- Gravity filtration tests to determine sludge dewaterability, varying pH and magnesium to phosphate ratios.
Main Results:
- Struvite formation significantly improved sludge dewaterability.
- Magnesium to phosphate ratios above 1.0 mol/mol showed no additional benefit.
- Increased pH negatively impacted dewaterability; optimal results were at pH 7.0.
- Stirring was more effective than aeration for dewaterability.
- Approximately 80% orthophosphate removal was achieved under optimal conditions.
Conclusions:
- Controlled struvite formation is an effective method for improving digested sludge dewaterability.
- Optimal dewatering occurs at lower pH (around 7.0) and with mechanical stirring.
- While struvite formation aids dewatering, polymer addition may still be necessary.
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