Comprehensive comparison of chemically enhanced primary treatment and high-rate activated sludge in novel wastewater treatment plant configurations

Anton Taboada-Santos; Enrique Rivadulla; Lidia Paredes; Marta Carballa; Jesús Romalde; Juan M Lema

doi:10.1016/j.watres.2019.115258

Comprehensive comparison of chemically enhanced primary treatment and high-rate activated sludge in novel wastewater treatment plant configurations

Water Res. 2020 Feb 1:169:115258. doi: 10.1016/j.watres.2019.115258. Epub 2019 Nov 1.

Authors

Anton Taboada-Santos¹, Enrique Rivadulla², Lidia Paredes³, Marta Carballa⁴, Jesús Romalde⁵, Juan M Lema⁶

Affiliations

¹ Department of Chemical Engineering, School of Engineering, Universidade de Santiago de Compostela, E-15782, Santiago de Compostela, Spain. Electronic address: anton.taboada@usc.es.
² Departamento de Microbiología y Parasitología, CIBUS-Facultad de Biología, Universidad de Santiago de Compostela, E-15782, Santiago de Compostela, Spain. Electronic address: enrique.rivadulla@usc.es.
³ Department of Chemical Engineering, School of Engineering, Universidade de Santiago de Compostela, E-15782, Santiago de Compostela, Spain. Electronic address: lidia.paredes@usc.es.
⁴ Department of Chemical Engineering, School of Engineering, Universidade de Santiago de Compostela, E-15782, Santiago de Compostela, Spain. Electronic address: marta.carballa@usc.es.
⁵ Departamento de Microbiología y Parasitología, CIBUS-Facultad de Biología, Universidad de Santiago de Compostela, E-15782, Santiago de Compostela, Spain. Electronic address: jesus.romalde@usc.es.
⁶ Department of Chemical Engineering, School of Engineering, Universidade de Santiago de Compostela, E-15782, Santiago de Compostela, Spain. Electronic address: juan.lema@usc.es.

PMID: 31710915
DOI: 10.1016/j.watres.2019.115258

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/m³ of wastewater) but had significantly higher operational costs than the HRAS-based configuration (6.0 vs 3.8 c€/m³ of wastewater). For OMPs with k_biol > 10 L/g_VSS·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.

Keywords: Chemically enhanced primary treatment; Energy demand; High-rate activated sludge; Operational costs; Organic micropollutants; Virus removal.

MeSH terms

Biological Oxygen Demand Analysis
Bioreactors
Carbon
Sewage*
Waste Disposal, Fluid
Wastewater*

Substances

Sewage
Waste Water
Carbon