NONEQUILIBRIUM TRANSPORT AND SORPTION OF ORGANIC-CHEMICALS DURING AQUIFER REMEDIATION

Aquifer remediation operations are often behind schedule. Usually, a r ather sharp concentration decrease shortly after the start of an opera tion is followed by a situation in which hardly any concentration decr ease is observed. Furthermore, the concentration increases after stopp ing the groundwater recovery. These phenomena are caused by so-called tailing. An important cause of tailing is the phenomenon that equilibr ium is not reached for some of the transport and sorption processes in volved. To predict these effects of tailing, IWACO has developed a pro gram SORWACO, which describes the behaviour of solutes along a path li ne. Processes for which equilibrium is reached quickly as well as proc esses for which equilibrium is reached only slowly are taken into acco unt. The program has been verified against breakthrough curves observe d in column experiments reported in the literature. The program parame ters were calibrated using the data of several experiments. The result ing set of parameter values accurately described the transport for dif ferent flow velocities. The fact that quite good results can be obtain ed without a lot of data from a specific site makes the program a valu able tool for the design of remediation operations. The program is esp ecially useful when extensive input data are not available so that det ailed three-dimensional or stochastic models cannot be applied. The us e of the program is illustrated by means of a case study. The progress was monitored and the data show good correspondence with the predicti ons of the program.