Comprehensive comparison of chemically enhanced primary treatment and high-rate activated sludge in novel wastewater treatment plant configurations. (1st February 2020)

• Record Type: Journal Article
• Authors: Taboada-Santos, Anton; Rivadulla, Enrique; Paredes, Lidia; Carballa, Marta; Romalde, Jesús; Lema, Juan M.
• Is Part Of: Water research. Volume 169(2020)
• Publication Date: 2020-02-01
• Subjects: Chemically enhanced primary treatment -- Energy demand -- High-rate activated sludge -- Operational costs -- Organic micropollutants -- Virus removal; Water -- Pollution -- Research -- Periodicals; 363.7394
• DOI: 10.1016/j.watres.2019.115258
• Languages: English
• ISSNs: 0043-1354

Abstract

Abstract: Novel wastewater treatment plants (WWTPs) are designed to be more energy efficient than conventional plants. One approach to becoming more energy efficient is the pre-concentration of organic carbon through chemically enhanced primary treatment (CEPT) or high-rate activated sludge (HRAS). This study compares these approaches in terms of energy demand, operational costs, organic micropollutants (OMP), and virus removal efficiency. A CEPT pilot-scale plant was operated at a hydraulic retention time (HRT) of 30 min, and a lab-scale HRAS reactor was operated at an HRT of 2 h and a solid retention time (SRT) of 1 d in continuous mode. A minimum dose of 150 mg/L ferric chloride (FeCl3 ) was required to achieve a threshold chemical oxygen demand (COD)-to-ammonium ratio below 2 g COD to 1 g of NH4 + –N (fulfilling the requirement for a partial nitritation-anammox reactor), reaching high phosphate (PO4 3− )-removal efficiency (>99%). A slightly lower COD recovery was attained in the HRAS reactor, due to the partial oxidation of the influent COD (15%). The lower PO4 3− removal efficiency achieved in the HRAS configuration (13%) was enhanced to a comparable value of that achieved in CEPT by the addition of 30 mg/L FeCl3 at the clarifier. The CEPT configuration was less energy-intensive (0.07 vs 0.13 kWh/m 3 of wastewater) but had significantly higher operational costs than the HRAS-based configuration (6.0 vs 3.8 c€/m 3 of wastewater). For OMPs with kbiol > 10 L/gVSS ·d, considerably higher removal efficiencies were achieved in HRAS (80–90%) than in CEPT (4–55%). For the remaining OMPs, the biotransformation efficiencies were generally higher in HRAS than in CEPT but were below 55% in both configurations. Finally, CEPT was less efficient than HRAS for virus removal. HRAS followed by FeCl3 post-treatment appeared to be a more effective alternative than CEPT for COD pre-concentration in novel WWTPs. Graphical abstract: Image 1 Highlights: CEPT and HRAS were holistically compared for maximum COD recovery in novel WWTPs. CEPT is less energy demanding than HRAS, but it leads to higher operational costs. HRAS achieves higher/comparable OMPs removal efficiency from wastewater than CEPT. CEPT was found less efficient than HRAS for viral removal from wastewater. HRAS results a preferable alternative than CEPT for COD recovery in novel WWTPs.