Effect of deposit age on adsorption and desorption behaviors of ammonia nitrogen on municipal solid waste

Abstract

Ammonia nitrogen pollution control is an urgent issue of landfill. This research aims to select an optimal refuse for ammonia nitrogen removal in landfill from the point of view of adsorption and desorption behavior. MSW (municipal solid waste) samples which deposit ages were in the range of 5 to 15 years (named as R(15), R(11), R(7), and R(5)) were collected from real landfill site. The ammonia nitrogen adsorption behaviors of MSW including equilibrium time, adsorption isotherms, and desorption behaviors including equilibrium time were determined. Furthermore, the effects of pH, OM, Cu(II), Zn(II), and Pb(II) on adsorption and desorption behavior of ammonia nitrogen were conducted by orthogonal experiment. The equilibrium time of ammonia nitrogen adsorption by each tested MSW was very short, i.e., 20 min, whereas desorption process needed 24 h and the ammonia nitrogen released from refuses was much lesser than that adsorbed, i.e., accounted for 3.20 % (R(15)), 14.32 % (R(11)), 20.59 % (R(7)), and 20.50 % (R(5)) of each adsorption quantity, respectively. The maximum adsorption capacity estimated from Langmuir isotherm appeared in R(15)-KCl, i.e., 25,000 mg kg(-1). The best condition for ammonia nitrogen removal from leachate was pH >7.5, OM 23.58 %, Cu(II) <5 mg L(-1), Zn(II) <10 mg L(-1), and Pb(II) <1 mg L(-1). Ammonia nitrogen in landfill leachate could be quickly and largely absorbed by MSW but slowly and infrequently released. The refuse deposited for 15 years could be a suitable material for ammonia nitrogen removal.