Efficient removal of Cr(Ⅲ)-carboxyl complex from neutral and high-salinity wastewater by nitrogen doped biomass-based composites

Heavy metals usually exist stably as the species of organic complexes in high-salinity wastewater.Therefore,their effective removal is challenging,especially when the initial p H is neutral.Herein,a novel nitrogen doped biomass-based composite(N-CMCS)was synthesized to remove the complexed heavy metal of Cr(Ⅲ)-carboxyl.The maximum adsorption capacity of Cr(Ⅲ)-Citrate(Cr-Cit)by N-CMCS under neutral p H(7.0)and high-salinity(200 mmol/L NaCl)condition was up to 2.50 mmol/g.And the removal performance remained stable after 6 times of regeneration.Combined with species and characterizations analysis,electrostatic attraction and hydrogen bonding were the main mechanisms for N-CMCS to remove Cr(Ⅲ)-carboxyl complexes.Dynamic adsorption indicated N-CMCS column could treat about 1300BV simulated wastewater and 350 BV actual wastewater with the concentration of effluent lower than1.0 mg/L.Furthermore,N-CMCS could remove a variety of complexed heavy metal ions under neutral p H,indicating the great potential in practical application.

Nitrification performance evaluation of activated sludge under high potassium ion stress during high-ammonia nitrogen organic wastewater treatment

The recycling reverse osmosis(RO)membrane concentrate of some high-ammonia nitrogen(NH_(4)^(+)-N)organic wastewater to the biological unit could cause potassium ion(K^(+))accumulation,thereby affecting the removal of NH_(4)^(+)-N by activated sludge.Thus,the effects of high K^(+) stress on activated sludge nitrification performance was studied.The results showed that the high K^(+) stress promoted the floc sludge to produce more extracellular polymers(EPS),which accelerated the sludge sedimentation and enriched the biomass in sequential batch reactors(SBRs).The ammonia oxidation process and nitrite(NO_(2)^(-)-N)oxidation process were further analyzed in the nitrification process.High K^(+) stress enriched ammonia oxidizing bacteria(AOB),which ensured the efficient ammonia oxidation process in SBRs,and ensured the removal rate of NH_(4)^(+)-N was maintained above 93%.However,high K^(+) stress(15g/L KCl)inhibited the activity of NO_(2)^(-)-N oxidizing bacteria(NOB)and reduced the abundance of NOB,thus leading to the accumulation of NO_(2)^(-)-N,and finally worsened the nitrification performance of activated sludge.In short,the performance of activated sludge will not be inhibited when the K^(+) in the wastewater does not exceed 5.23 g/L.The results could provide a reference for the optimization of the biological performance in treating high-NH_(4)^(+)-N organic wastewater with activated sludge coupled RO membrane treatment process.