Volume 5 - 2003

The formation of chlorination by-products (CBPs) was investigated by bench-scale chlorination experiments
with surface waters from different sources in Lesvos island, Greece. The main factors studied were
organic matter content of water (expressed as UV-272 absorbance), time and chlorine dose. The CBPs,
determined by gas chromatographic techniques, belong to the categories of trihalomethanes (THMs),
haloacetic acids (HAAs), haloacetonitriles, chloral hydrate and chloropicrin. HAAs and THMs were the
most abundant CBPs detected in the chlorinated samples, while haloketones, haloacetonitriles and chloral
hydrate occurred at much lower concentrations. Statistical analysis of the results with multifactor
analysis of variance revealed the influence of the parameters studied on the formation of individual compounds.
Application of principal component analysis (PCA) provided a clear picture of the differentiations
between varying water sources and chlorination conditions. Multiple regression was used for development
of predictive models for CBPs formation. The proposed models are considered satisfactory for
predicting CBPs concentrations for water sources and chlorination conditions similar to those examined.

A pilot-plant study was carried out with the water supply to Athens water works filtered through a granular
activated carbon (GAC) filter- adsorber. The objective of this study was to evaluate the performance
of GAC for the removal from drinking water of the two main groups of disinfection by -products
(DBPs), trihalomethanes (THMs) and haloacetic acids (HAAs), as well as of dissolved organic matter.
The pilot treatment facility is located at the Water Treatment Plant of EYDAP in Galatsi, Athens, and
was operated as a rapid gravity filter - adsorber. It was fed with chlorinated water, coming from the
overflow of the sedimentation tanks, and operated continuously in parallel with a full-scale sand filter.
At regular time intervals water samples were taken from both filters and analysed for THMs, HAAs
and DOC. Other parameters were measured too. The operation of the GAC filter-adsorber continued
until the GAC adsorption capacity for THMs and HAAs was almost exhausted.
The results of the analyses showed that GAC was more effective in removing the dissolved organic matter
than the smaller molecules of THMs and HAAs, fact which is in agreement with the relevant literature.
GAC was also proved more effective in removing HAAs than removing THMs. The removal of
THMs and the most part of the removal of HAAs and DOC must be attributed to adsorption by GAC,
while that of a smaller part of DOC and HAAs may be attributed to biological activity in the filter
bed, where chlorine had been totally removed by the catalytic action of the activated carbon surface.

The scope of this paper is the evaluation of wastewater reuse quality criteria and treatment specifications,
appropriate to Greek conditions. The parameters that affect wastewater reuse criteria were taken
into consideration, concerning among others reuse priorities, available treatment plants and effluent
characteristics. The proposed wastewater reclamation criteria were verified by a series of lab-scale
experiments, designed to study the feasibility and effectiveness of the following treatment schemes to
produce treated wastewater suitable for reuse: a) disinfection of secondary effluent with UV radiation
and chlorination and b) tertiary treatment and disinfection of wastewater with UV radiation and chlorination.
The experimental data were analyzed using a stochastic statistical model that employs Monte
Carlo simulation. The main scope of the stochastic approach was the regeneration of a greater set of
data, based on the defined by the experimental information mathematical distribution of each parameter
involved and the determination of relative probability distributions. Following this approach the
standards proposed are realistic and feasible and in the case of restricted reuse can be readily achieved
by the existing wastewater treatment plants in Greece. Even in the case of unrestricted reuse the additional
treatment required can be achieved at a moderate cost, through upgrading of the existing plants
with tertiary treatment.

The paper discusses a methodology for integrated municipal wastewater management. In compliance
to the EU Directive 91/271, there is a legal binding to ensure that all agglomerations with populations
over 2000 are provided with wastewater collecting system and adequate treatment. The conditions for
optimum application of the Directive in Greece, especially in the light of the recent administrative reorganization,
and the management of small rural communities not covered by the Directive are
addressed, with reference to a case study application in the Achaia County. In compliance to the EU
Directive 91/271, it is estimated that collecting systems and treatment should expand to at least 70% of
the total population. However, due to the expanding touristic activity, the limited availability of land,
environmental considerations, and favorable population characteristics (high density, relatively large
communities) and morphological and socioeconomical conditions, it is proposed that coverage can
reach to 85% of the total population. As for the rest of the County population (15%), decentralized on
site wastewater treatment and disposal schemes were proved to be the most technically effective and
economically efficient alternative.