Georgios D. Gikas

Water Quality Trends in a Coastal Lagoon Impacted by Non-point Source Pollution after Implementation of Protective Measures

Water quality data from two different monitoring periods are used to evaluate the trophic state and effectiveness of various protective measures on the restoration of a eutrophic, coastal Mediterranean lagoon. Main protective measures included elimination of municipal/industrial raw wastewater discharges in the rivers outflowing to the lagoon, sediment/erosion control practices in the lagoon’s drainage basin (i.e., construction of sediment/debris dams and grade control structures, reforestation and ban on livestock grazing), and reduction of fertilizer application quantities as a result of changes in crops. Water quality data include, among others, chlorophyll a, dissolved oxygen and nutrient concentrations, various physicochemical parameters, and transparency, measured during two monitoring periods, i.e., before (1983–84) and after (1998–99) implementation of protective measures. Rainfall depth for the two time periods was also available. Empirical equations were developed, from statistical analyses of the data, relating the water quality parameters during the two monitoring periods. These models help identify water quality trends. Based on the analyses, it seems that measures were effective in reducing sediments transported into the lagoon. However, the lagoon remains eutrophic to hypereutrophic, mostly due to phosphorus released in the water column from bottom sediments. Therefore, future restoration efforts should be directed towards the management of bottom sediments.

On-site treatment of domestic wastewater using a small-scale horizontal subsurface flow constructed wetland

A small-scale horizontal subsurface flow constructed wetland, located in North Greece, was designed and constructed to treat wastewater from a single-family residence. A three-year monitoring program was undertaken to evaluate the performance of this system. The monitoring campaigns were organized every 7 days. Water quality samples were collected at the inlet, at intermediate points (i.e. at the end of each treatment stage) and at the outlet of the system. Temperature, electrical conductivity, pH and DO were measured in-situ with the use of appropriate instruments at the same points of water sample collection. Water samples were analyzed for BOD, COD, TKN, ammonia, nitrate, nitrite, total phosphorus (TP), ortho-phosphate (OP), total suspended solids (TSS) and total coliforms (TC). Mean removal efficiencies for the monitoring period were: 86.5% for BOD, 84.6% for COD, 83.7% for TKN, 82.2% for ammonia, 63.1% for OP, 63.3% for TP, 79.3% for TSS and 99.9% for TC. Furthermore, based on statistical testing, TKN, ammonia and TP removal efficiencies showed dependence on temperature. The paper presents facility description, study details and monitoring results. The study shows that the use of constructed wetlands in wastewater treatment is a good option for single-family residences in rural areas.

Evaluation of evapotranspiration in small on-site HSF constructed wetlands

Experimental results on evapotranspiration (ET), relevant to small on-site facilities are presented, derived from one-year controlled experiments in five pilot-scale horizontal subsurface flow (HSF) constructed wetlands (CW) used as lysimeters. The CW units operated in Northern Greece. They were rectangular tanks made of steel, with dimensions 3m long, 0.75m wide and 1m deep. Three different porous media were used, i.e., medium gravel, fine gravel and cobbles. Two plants were used, namely common reed (R, Phragmites australis) and cattails (C, Typha latifolia). One unit was unplanted. ET was estimated based on the water budget method. Conclusions were drawn on its relation to season and vegetation density. Furthermore, Pearson correlation coefficient analysis identified the main factors affecting wetland plant ET. Seven well-known ET empirical methods were applied to estimate ET using the measured meteorological and wetland data. ET estimated by the empirical methods were multiplied with appropriate correction coefficients to match measured ET, providing this way appropriate plant coefficient (Kc) values, and equations for predicting HSF CW evapotranspiration. The suitability of these methods for the particular constructed wetland type is discussed through comparison with the measured data. The Blaney-Criddle method was found as best. Furthermore, stepwise multiple linear regression analysis was used with the measured ET and meteorological data to produce simple empirical equations to predict ET rates according to meteorological factors, plant and substrate material.

Water quality trends in Polyphytos reservoir, Aliakmon River, Greece

A water quality monitoring program was undertaken from June 2004 to May 2005, on a monthly basis, in Polyphytos Reservoir of Aliakmon River. Depth, water temperature, dissolved oxygen, conductivity, pH and transparency (Secchi disk) were measured in situ, while collected water samples were analyzed in the laboratory for the determination of BOD, COD, total phosphorus (TP), ortho-phosphate (OP), chlorophyll-a (Chl-a), ammonium, nitrite and nitrate, total Κjeldahl nitrogen (TKN) and heavy metals (Fe, Mn, Cu, Cr, Pb, Ni and Cd). Measured concentrations were compared to those from two previous studies conducted in July 1987 to June 1988 and January 1991 to February 1993. The following conclusions are drawn: the effect of the watershed on the lake environment, mostly through Aliakmon River, is significant, and it accelerates the eutrophication of the lake. The anoxic zones, which were defined in the lake, reinforce this conclusion. Nitrate, nitrite and ammonia were measured at lower concentrations compared to previous studies, while total phosphorus and chlorophyll-a were found at increased concentrations. The current trophic state of Polyphytos reservoir is eutrophic, based on the OECD method and Carlson’s Trophic State Indices (TSI). The concentration of BOD and COD ranged at low levels. Furthermore, the mean concentrations of metals Fe, Mn, Cu, Cr, Pb, and Cd were below the potable water standards set by WHO and EU. During most part of the study period the ratio N/P for Polyphytos reservoir was higher than 7.2:1, and therefore, phosphorus is the limiting nutrient for algal growth.

Performance and modeling of a vertical flow constructed wetland–maturation pond system

A 32-month monitoring program is presented in a vertical flow constructed wetland facility, located in North Greece. The monitoring campaigns were organized every 15 days. Water quality samples were collected at the inlet, at four intermediate points (i.e., at the end of each treatment stage) and at the outlet of the system. Temperature, electrical conductivity, pH and dissolved oxygen (DO) were measured in-situ with the use of appropriate instruments at the same points of water sample collection. Water samples were analyzed for biochemical oxygen demand (BOD), chemical oxygen demand (COD), total Kjeldahl nitrogen (TKN), ammonia, nitrate, nitrite, total phosphorus (TP), ortho-phosphate (OP), total suspended solids (TSS) and total coliforms (TC). Mean removal efficiencies for the monitoring period were: 90.8% for BOD, 89.0% for COD, 83.9% for TKN, 83.8% for ammonia, 38.8% for TP, 17.4% for OP, 90.4% for TSS and 99.9% for TC, indicating, for most pollutant, excellent performance of this constructed wetland (CW) system under Mediterranean climate conditions. Results showed that organic matter, TSS, TKN, ammonia, TP, OP and TC removal is not significantly affected by temperature. The collected removal data were used to produce appropriate parameter values for first-order k-C* models and develop simple models based on stepwise multiple linear regression (SMLR) analysis, in an effort to predict CW performance. These models were verified using data from another facility located in the same region. The results showed that the predictions correlate well with measured values, leading to the conclusion that the first-order models and the developed SMLR models are useful tools in the design of vertical flow (VF) CWs.

Suitability of Water Quality Indices for Application in Lakes in the Mediterranean

Water quality indices (WQIs) are efficient and powerful tools for evaluating, organising and communicating information on the overall quality of surface water bodies. The use of these indices may be very helpful in evaluating the water quality of aquatic systems in relation to the EU Water Framework Directive (WFD). In this study, two well-known water quality indices have been selected for evaluation: the CCME (Canadian Council of Ministers of the Environment) and NSF (National Sanitation Foundation). These WQIs were applied in the Polyphytos reservoir-Aliakmon river in Greece where monthly water quality data were available for the period June 2004 to May 2005. The available dataset included values of the following parameters: water depth, water temperature, dissolved oxygen, electrical conductivity, pH, transparency (Secchi disk depth), BOD5, COD, total phosphorus (TP), chlorophyll-a (Chl-a), ammonium (NH4+), nitrite (NO2−) and nitrate (NO3−), and total Κjeldahl nitrogen (TKN). The application of the two WQIs was made using specialised, freely available software-tools. A comparison of their performance and a qualitative judgement on their suitability on expressing the quality of a surface water body is presented. The classification results were compared with those obtained by the WFD-ECOFRAME approach of the EU. Based on the applicability and drawbacks of the examined indices, useful conclusions were derived and discussed. Among others, it is concluded that the NSF-WQI is a more robust index and produces a classification nearer that of the WFD-ECOFRAME approach when compared to the CCME-WQI.

Hydrodynamic and nutrient modeling in a Mediterranean coastal lagoon

The USEPA WASP5 modeling system was applied to simulate and evaluate the relationships between external and internal nutrient loadings and water quality of Vistonis lagoon, North Greece for a 2-year time period. The hydrodynamic model DYNHYD5 was calibrated to estimate daily lagoon water level. The water quality models TOXI5 and EUTRO5 were calibrated and verified using meteorological data from a station near the lagoon, and field data (salinity, dissolved oxygen, nutrients and chlorophyll-a concentrations) from seven stations located in the lagoon, for the time period April 1998 to May 1999. Predicted by the model salinity, dissolved oxygen, total phosphorus, total inorganic nitrogen and chlorophyll-a were plotted against observed values and showed good agreement. Model performance was evaluated using scattergrams of predicted versus observed values and the Kolmogorov-Smirnov two-sample goodness-of-fit test at p < 0.05. Sediment sources of nitrogen and phosphorus were important to achieve a successful model calibration. The validated model was also used to test the effectiveness of alternative management scenarios in relation to improvement of the trophic state of the lagoon.

Water quantity and quality assessment of lower Nestos river, Greece

Monitoring quantity and quality data of a 3-yr (2006–2009) survey in the lower reach of Nestos river are presented. For the purposes of this study, monitoring was taking place at six sites along the river course. Discharge measurements were made at four stations. Physicochemical parameters (i.e., electrical conductivity, pH, dissolved oxygen and water temperature) were measured in situ while water quality samples were collected on a bi-weekly basis at all six stations along the river. Water samples for chemical analyses were collected for the determination of total phosphorus, orthophosphate, nitrite and nitrate nitrogen, ammonia, biochemical oxygen demand (BOD), chemical oxygen demand (COD), chlorophyll-a, TSS, alkalinity, sulfuric and chloride anions, major cations (Na+, K+, Mg+, Ca+) and metals. Two autographic telemetric stations also provided continuous stage and water quality data at two of the sites. ANOVA and t-test statistical analysis were used for the interpretation of the collected data. Nutrient concentrations were found within acceptable limits, while bicarbonates were the dominant ions. No significant seasonal and spatial variations were observed, suggesting little impact from human activities on the part of river basin under investigation.

Spatial and temporal changes of water quality, and SWAT modeling of Vosvozis river basin, North Greece

The results of an investigation of the quantitative and qualitative characteristics of Vosvozis river in Northern Greece is presented. For the purposes of this study, three gaging stations were installed along Vosvozis river, where water quantity and quality measurements were conducted for the period August 2005 to November 2006. Water discharge, temperature, pH, dissolved oxygen (DO) and electrical conductivity (EC) were measured in situ using appropriate equipment. The collected water samples were analyzed in the laboratory for the determination of nitrate, nitrite and ammonium nitrogen, total Kjeldalh nitrogen (TKN), orthophosphate (OP), total phosphorus (TP), COD, and BOD. Agricultural diffuse sources provided the major source of nitrate nitrogen loads during the wet period. During the dry period (from June to October), the major nutrient (N, P) and COD, BOD sources were point sources. The trophic status of Vosvozis river during the monitoring period was determined as eutrophic, based on Dodds classification scheme. Moreover, the SWAT model was used to simulate hydrographs and nutrient loads. SWAT was validated with the measured data. Predicted hydrographs and pollutographs were plotted against observed values and showed good agreement. The validated model was used to test eight alternative scenarios concerning different cropping management approaches. The results of these scenarios indicate that nonpoint source pollution is the prevailing type of pollution in the study area. The SWAT model was found to satisfactorily simulate processes in ephemeral river basins and is an effective tool in water resources management.

Water Quality of Drainage Canals and Assessment of Nutrient Loads Using QUAL2Kw

The water quantity and quality in two of the four main drainage canals located in the plain of Chryssoupolis in Kavala, North Greece, are studied. The area is intensively used for agriculture. Irrigation water is supplied by Nestos River, using a network of irrigation canals. Drainage water and irrigation return flows are collected in the four main drainage canals, which outflow into the Thracian Sea, North Aegean. A monitoring program in the four canals was designed to monitor flow and main constituents of drainage water. Main pollutants included nitrate, phosphorus and suspended solids. Based on the collected data, the trophic state of the canals and its seasonal variation were assessed, and the limiting nutrient was identified. QUAL2Kw was also used to model flow and water quality in two of the four canals. The calibration and verification of QUAL2Kw was undertaken using the collected field data, in an effort to identify the pollution sources and propose future management actions for the improvement of drainage canal water quality. The results showed that QUAL2Kw is a useful tool to simulate water quality in rivers and canals, and to quantify the impacts of non-point source pollution from agricultural areas.