Optimization of ozonation process for organic matter and ecotoxicity removal from landfill leachate by applying rotatable central composite design (RCCD)

Abstract

Ozonation process was used for leachate treatment from a landfill located in Rio de Janeiro, Brazil. The influence of pH and ozone concentration on COD (Chemical Oxygen Demand), TOC (Total Organic Carbon), Absorbance at 254 nm (ABS254nm), and True color was evaluated through RCCD (Rotatable Central Composite Design) experimental design, resulting in mathematical models that were statistically analyzed in Statistica and Design Expert software. The removals obtained was up to 26.1%, 29.9%, 56.9%, and 97.9% for COD ([COD]₀=3,323 mg/L), TOC ([TOC]₀=1,275 mg/L), ABS254nm (ABS₀=32.2), and True color ([True color]₀=3,467 mgPt-Co/L), respectively. Statistical and variance analysis of the experimental data revealed that one quadratic model obtained in Statistica was valid, ABS254nm reduction. However, by applying the Design Expert software, modified models were generated to predict the behavior of all dependent variables. Thus, the optimum point for the best response after ozonation of the landfill leachate was at the highest pH and the lowest ozone dose (9 and 2.2 mgO₃/m³, respectively). Toxicity toward Allivibrio fischeri bacteria was abated at the same time that it decreased the impact of the effluent to Danio rerio fish (from 125 UT to 62 UT) on the treated leachate.

GRAPHICAL ABSTRACT

Keywords:

• Landfill leachate
• wastewater treatment
• experimental design
• ozonation
• ecotoxicity

Disclosure statement

The authors declare that they have no competing interests.

Funding

The authors would like thank the Fundação de Amparo à Pesquisa do Estado do Rio de Janeiro - FAPERJ - for the financial support of the study, project number: E26/010.002064/2015 and E26/010.001868/2015.

Data availability statement

The data that support the findings of this study are available from the corresponding author, F.V.F., upon reasonable request.

Appendix A

Figure A1. Modified pseudo-first order kinetics of COD, ABS_254nm, True color, and TOC removal.

Figure A2. 2D graphs of COD, ABS_254nm, True color, and TOC removal as a function of pH and ozone concentration.

Figure A3. Graph interactions of COD, ABS_254nm, True color, and TOC removal as a function of pH and ozone concentration.

Additional information

Notes on contributors

Heloisa B. Bastos

Heloisa B. Bastos, MSc, Chemical Engineer; Master’s Degree in Chemical and Biochemical Processes Field; expertise in experimental design, ozonation, and leachate treatment.

Larissa L. S. Silva

Post-doc Larissa L. S. Silva, DSc, Industrial Chemist; Master’s and Doctor’s Degree in Chemical and Biochemical Processes Field; expertise in water and effluents treatment and reuse, oxidative technologies, removal of micropollutants and organic contaminants in water/wastewater, polymeric membranes development, synthesis of nanoparticles.

Érika C. A. N. Chrisman

Professor Érika C. A. N. Chrisman, DSc, Industrial Chemist; Master’s and Doctor’s Degree in Chemistry Field; expertise in oil and petrochemicals, organic processes optimization, separation processes, and experimental design.

Fabiana V. Fonseca

Professor Fabiana V. Fonseca, DSc, Chemical Engineer; Master’s and Doctor’s Degree in Chemical and Biochemical Processes Field; expertise in advanced oxidative processes, treatment and reuse of water and industrial effluents, removal of micropollutants in water, physicochemical processes, and application of nanoparticles in water treatment.

Juacyara C. Campos

Professor Juacyara C. Campos, DSc, Chemical Engineer and Chemist; Doctor’s Degree in Chemical Engineer; expertise in pollution control, waste landfill leachate, solid waste, effluent treatment, wetlands, refinery effluent, toxicity assessment, water treatment and effluent reuse.