Issue 2

The aim of the present paper is to give a systematic and critical presentation of important existing
analytical solutions for transient stream-aquifer interaction, which can be used to give answers to
simple interaction problems or to verify mathematical models. Stream-aquifer interaction is the most
common subject of papers discussing surface water-ground water interaction and a review of
analytical solutions to the problem is lacking from the literature. The analytical solutions presented in
the paper are firstly distinguished based on whether only the ground water flow equations or both the
ground water and stream flow equations are solved for their derivation and secondly based on the
type of aquifer (confined or unconfined) interacting with the stream and on the type of equations
solved. The literature review showed that there is only a small number of publications, where the
authors consider both the ground water and the stream flow equations for the development of the
analytical solutions. The majority of the available analytical solutions of stream-aquifer interaction
are derived by solving only the ground water flow equations, taking into account the stream water
level as a boundary condition.
For each analytical solution presented in the paper, its accuracy, its ease of application to simple
interaction problems and its suitability for the verification of mathematical models are discussed in
detail. Specifically for the case of predicting the water table level in unconfined aquifers interacting
with streams, an analytical solution of the non-linear Boussinesq equation is compared to two
analytical solutions of different linearized forms of the Boussinesq equation, in order to quantify the
error in estimating the water table level when using a linear solution. Among the very few analytical
solutions found in the literature, where the authors consider both the stream flow and ground water
flow equations for their development, the most comprehensive one is chosen to give an application
example, which can be used as a benchmark case for the verification of integrated stream-aquifer
mathematical models.

One of the most favorable and cost-saving methods to counteract water quality deterioration in a
harbor basin is the use of flushing culverts, which reduce flushing times and avoid areas of low flow
and eddies formation. In the present paper, results of experiments carried out in a 2-D facility in
order to investigate wave and dissolved oxygen transmission in harbor basins through flushing
culverts are presented and analyzed. Incident wave and transmitted wave heights were determined
using wave gauges for various combinations of wave characteristics and geometric characteristics
of the flushing culverts. An empirical equation using regression analysis was derived, which
correlates the wave transmission coefficient with the characteristics of the waves and the
geometrical characteristics of the flushing culvert. Further the oxygen transmission coefficient
through flushing culverts, was expressed as a function of the characteristics of waves and the
dimensions of the flushing culvert. The comparison of calculated and experimental data is very
encouraging. Though, the verification of the proposed equation with even more extended
experimental data and real scale measurements is needed in order to be used in the design
process.

An Upflow Anaerobic Sludge Bed (UASB) reactor was used to evaluate mesophilic anaerobic
treatment of a pre-acidified fruit wastewater. The system was operated at increasing volumetric
loading rates by sequentially increasing wastewater flowrate. The operational temperature was
maintained initially at 37 oC and consequently decreased to 30 and 25 oC. For the volumetric loading
rates examined i.e. 5-35 KgCOD m-3d-1), the UASB attained COD removal levels higher than 70%.
The first-order kinetics were found to be suitable for representation of the substrate removal. The
kinetic constant decreased from 23 to 21 and 19 d-1 at 37, 30 and 25 oC respectively. Prediction of
effluent COD and methane production rate during continuous reactor operation was possible using
the first-order kinetic model.

Rice husk carbon (RHC) has the ability to adsorb the dyestuff from aqueous solution. It may be
useful low cost adsorbent for the treatment of effluents, discharged from textile industries. The
effectiveness of RHC have been tested for the removal of colour from the wastewater samples
containing three dyes namely crystal violet, direct orange and magenta. Effect of various parameters
such as agitation time, pH, temperature, adsorbent dose and concentration have been investigated
in the present study. The adsorption of dyes have been best described by pseudo first order
mechanism and Freundlich adsorption isotherms. The rate constant of adsorption (Kad) have been
determined, which are found to be 6.8 x 10–3, 8 x 10–3 and 10 x 10–3 min–1 for crystal violet, direct orange
and magenta respectively. Similarly the Freundlich constants related to the adsorption capacity (Kf) are
found to be 0.74, 0.44 and 0.68 g l–1 and intensity of adsorption (n) are found to be 0.41, 0.73 and
0.33 mg g–1 for above dyes respectively.