Application of hydration reaction on the removal of recalcitrant contaminants in leachate after biological treatment

• Hydration reaction was applied for the advanced wastewater treatment.
• Recalcitrant contaminants and NH3 was removed efficiency by hydration reaction.
• The reaction mechanism of hydration reaction in leachate treatment was predicted.

Leachate contains amounts of non-biodegradable matters with COD range of 400–1500 mg/L after the biological treatment, and should be removed further to attain the Chinese discharge standards. Hydration reaction has the potential to combine and solidify some recalcitrant substances, and thus could be applied as the advanced leachate treatment process. It was found that COD and NH3N decreased from 485 to <250 mg/L and 91 to 10 mg/L, with the removal rate over 50% and 90% in the first 6 d, respectively, and COD and NH3N removal capacity were around 23.7 and 9.2 mg/g under the test conditions. The percentage of the substances with low Mn range of <1000 decreased from 32.9% to 3.2% in leachate after hydration reaction. Tricalcium aluminate, tricalcium silicate and dicalcium silicate were the most activity compounds successively for the pollutant removal in leachate, and hydration reaction could be the option for the advanced wastewater treatment process thereafter.