Evaluation of coagulation–flocculation and nanofiltration processes in landfill leachate treatment

Abstract

Landfill leachate consists mostly of a high content of refractory organic matter, ammonia and toxic compounds. All these compounds, regardless of their nature, have a potential pollution effect on local ground and surface waters. In this context, the purpose of the present study was to evaluate a treatment process (coagulation–flocculation with lime coupled with nanofiltration) applied to landfill leachate from Seropédica, Rio de Janeiro (Brazil). Jar tests were conducted to determine the optimum dosage of lime (ranged from 0 to 10 g L⁻¹) and, at optimum lime dose, ammonia nitrogen was removed during coagulation–flocculation process due to high pH. The process was settled for 6 h with slow stirring (50 rpm) to promote air entrainment and NH₃-N stripping before using the final treatment step of nanofiltration at 8 bar. After ammonia stripping, NH₃-N was reduced from 1,236 mg L⁻¹ to 353 mg L⁻¹ (71% removal efficiency). At the end of the combined treatment, TOC (total organic carbon), HS (humic substances) and COD (chemical oxygen demand) removals were 89%, 80% and 94%, respectively. The results showed that the combined process was effective in the removal of recalcitrant compounds and NH₃-N.

Keywords:

• ammonia stripping
• coagulation–flocculation
• landfill leachate
• lime
• nanofiltration

Acknowledgments

The authors would like to thank COMLURB (Companhia Municipal de Limpeza Urbana - Rio de Janeiro) (Municipal Urban Cleaning Company–Rio de Janeiro City) for sending samples of leachates.

Additional information

Funding

The authors gratefully acknowledge the Conselho Nacional de Desenvolvimento Científico e Tecnologico – CNPq - Scholarship and FAPERJ - Fundaçäo Carlos Chagas Filho de Amparo à Pesquisa do Estado do Rio de Janeiro - # 202.923/2018.