Treating both wastewater and excess sludge with an innovative process

Area of Science:

• Environmental Engineering
• Water Treatment Technologies
• Bioreactor Systems

Background:

• Conventional wastewater treatment often generates excess sludge, posing disposal challenges.
• Integrated systems are needed to improve pollutant removal and sludge management.
• Membrane bioreactors (MBR) are effective but can produce significant sludge volumes.

Purpose of the Study:

• To develop and evaluate an innovative wastewater treatment process integrating biological treatment with ozonation for excess sludge.
• To enhance the removal of key pollutants including chemical oxygen demand (COD), ammonia nitrogen (NH3-N), total nitrogen (TN), and total phosphorus (TP).
• To achieve a zero sludge withdrawal state through sludge ozonation and internal recycling.

Main Methods:

• Utilized an aerobic membrane bioreactor (MBR) for organics and nitrogen removal.
• Incorporated an anaerobic reactor for enhanced phosphorus release from sludge.
• Treated excess sludge from the MBR using an ozonation unit before returning it to the MBR.
• Conducted batch tests to determine specific nitrification and denitrification rates.

Main Results:

• Achieved high removal efficiencies: 93.17% for COD, 97.57% for NH3-N, 82.77% for TN, and 79.5% for TP.
• Observed specific nitrification and denitrification rates of 1.03 and 0.56 mg NH3-N/(gMLSS x h), respectively, with denitrification as the rate-limiting step.
• Successfully implemented a zero excess sludge withdrawal strategy over a two-month experimental period.
• Determined the additional ozonation operating cost to be minimal (USD 0.0054/m³ wastewater).

Conclusions:

• The integrated biological and ozonation process is highly effective for wastewater treatment and sludge management.
• Zero excess sludge withdrawal is achievable, significantly reducing disposal burdens.
• The process offers an economically viable solution for advanced wastewater treatment.