Qualitative monitoring of tertiary treated wastewater reuse extensive distribution system: total coliforms number and residual chlorine concentration.

During a 5-month summer period, samples of tertiary treated wastewater flowing in an extensive distribution system composed of storage tanks and pipes were collected at 2-week intervals, from 21 different sampling points, including the exit from the wastewater treatment plant (WWTP). The WWTP producing this effluent treated one of the most popular European tourist resorts on the north coast of the island of Crete, at the southernmost point of Greece. The average summer equivalent population treated by the plant exceeded 50,000, falling to under 5,000 in the winter. The samples were analyzed for total coliforms number (TC in cfu / 100 mL) and residual chlorine concentration (RCHL in mg/L). In almost 60% of the samples the TC number was so large that it could be safe to suggest that the WWTP and distribution system failed to reach the EPA standards for wastewater reuse for tree irrigation (faecal coliforms < or = 200 cfu/100 mL and RCHL < 1 mg/L) due mainly to inflow and septage handling, above designed limits. The licensing operational and reuse standards were set in TC < or = 500 cfu/100 mL, where 76% of the analyzed samples recorded larger values. It was also estimated that in 14% of the samples the wastewater quality failed to reach even the less strict WHO standards of FC < or = 1.000 cfu/100 mL. When chlorination was properly adjusted the effluent quality was improved (last three sets of samplings for each collection point), helped by the WWTP inflow decrease. As a result the values recorded in all tanks and collectors were also improved. However, even then, the required licensing standards were randomly and barely achieved. This suggests that specific wastewater quality standard at the exit of a WWTP do not guarantee that the wastewater will still retain these characteristics at its final application point.

Integrated wastewater management reporting at tourist areas for recycling purposes, including the case study of Hersonissos, Greece.

Wastewater treatment facilities in tourist areas, in comparison to other municipal facilities, require specific configurations and additional management actions in order to achieve a reliable and cost-effective treatment. For example, the same facility operates during winter with minimum flows and in summer with peak flows. Moreover, careful effluent management is required to minimize environmental impact and health effects on tourists. In this study, effluent management data, including quantitative and qualitative effluent characteristics, reuse, and economic aspects of the Hersonissos Wastewater Treatment Plant (WTP) in Greece, are discussed. It has been designed to treat both municipal wastewater from the Hersonissos Municipality and septage from the wider area. Analysis of effluent quantitative data showed two flow peaks in the summer period and only one in winter. The WTP was found to provide a reliable level of treatment in terms of biochemical oxygen demand (95.9%), total suspended solids (97.2%), and total nitrogen (87.7%) removal, but increased numbers of fecal coliforms were measured at some peak flow periods, suggesting the need for additional management strategies. Effluent is reused mainly for agricultural irrigation; secondary uses include fire protection and landscape irrigation. Economic analysis showed that for each cubic meter treated, the total annual economic cost for treatment, filtration, and reuse infrastructure was 1.07 euro, 0.05 euro, and 0.08 euro, respectively.