Spatial and Temporal Characterization of Olive Mill Wastewater in Cyprus
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SPATIAL AND TEMPORAL CHARACTERIZATION OF OLIVE MILL WASTEWATER IN CYPRUS C. C. ANASTASIOU*1, P. GRAFIAS2, T. P. LAMBROU3, A. KALLI1 *Corresponding Author – e-mail: [email protected] 1Department of Civil Engineering, Frederick University, 7 Y. Frederikou Street, 1036 Nicosia, Cyprus 2Frederick Research Centre, Frederick University, 7 Y. Frederikou Street, 1036 Nicosia, Cyprus 3KIOS Research Center for Intelligent Systems and Networks, University of Cyprus, Nicosia, Cyprus SUMMARY: Cyprus belongs to the group of Mediterranean countries which have difficulties in dealing with Olive Mill Wastewater (OMWW) management and treatment. To better facilitate subsequent management and treatment measures to be enforced in Cyprus, a survey that seeks to spatially and temporally characterize OMWW on the island was undertaken. Our survey identified that 26 olive mills were in operation during the years 2010-2012, producing an estimated 60,000 tons of OMWW per year. A spatial map of the industry was produced during the first half of our survey. In the second half, eight olive mills were selected for sampling and analysis of wastewater based on factors that could influence the composition of OMWW produced on each site. OMWW samples were being tested for chemical and biochemical oxygen demand (COD, BOD), nitrogen and phosphorous content, pH, total phenolic content, color, total suspended solids (TSS) and total solids (TS). Phytotoxocity analysis of wastewaters has not been completed yet. Trends on the nature and variability of OMWW have been identified, while time and space variables form the central axes for the statistical analysis. The results of this characterization study are presented in this paper. 1 INTRODUCTION Olive mill wastewater (OMWW), generated by the olive oil extraction process, is the main waste product of this industry. OMWW is characterized by dark coloration, high organic content, and phytotoxic constituents. The improper disposal of OMWW to the environment, or to domestic wastewater treatment plants, is prohibitive due to its potential threat to surface and groundwater integrity, or due to its toxicity to microorganisms used in treatment plants. OMWW poses a major environmental challenge in countries of the Mediterranean basin, especially considering that Mediterranean countries are responsible for 95% of the world’s olive production. In Cyprus, the most common practice for the management of OMWW, currently, includes the use of evaporation ponds and the subsequent discharge of solids in landfills and/or on soil. While evaporation ponds offer a good way to reduce the liquid portion of the waste, they do very little in reducing the toxicity of the waste, while they simultaneously impart an odor problem to the areas where such waste is stored. Furthermore, evaporation results in the loss of large quantities of water, which is an important and limited resource in Cyprus. In the attempt to identify methods and technologies that better lend themselves for the treatment of OMWW, it is of utmost importance to properly and safely characterize this type of wastewater, as much through space as well as through time (during a harvesting season). The specific objective of this study was the spatial and temporal characterization of OMWW in Cyprus. The absence, to date, of such data, for Cyprus, presented a weakness in the waste management process for the olive-oil industry of the country. It is expected that the data, on the nature and (spatial/temporal) variability of OMWW in Cyprus, will become an indispensable tool in the hands of scientists, engineers, and environmental managers who seek to implement effective and efficient wastewater treatment technologies, or waste management plans. 2 SURVEY OF THE OLIVE MILL INDUSTRY IN CYPRUS The starting point of this effort was the identification of registered olive mills in the island. According to data obtained from governmental sources, approximately 35 olive mills are registered in Cyprus producing an estimate of 7500 tons oil per year. Water use in oil production is about four times the amount of oil produced, suggesting that Cyprus produces 26,000 tons/year of olive mill wastewater. However, our own country-wide survey showed that only 26 olive mills remained in operation during the years 2010 – 2012 producing an estimated 60,000 tons of OMWW per year. This reduction in the number of mills occurred due to the closing of some or the merging of certain others. Out of the 26 mills, currently in operation, in Cyprus, 25 mills were identified to be using the three-phase process of oil extraction which is a continuous system which working by means of the centrifugation of the beaten olive paste, producing three products: oil, pomace and residual water. Only one mill on the island uses the two-phase method, which is a rather older method of olive oil extraction. Our survey also identified two olive species that are predominant in the production of oil on the island. Specifically the Koroneiki and Cypriot (Kipriaki) varieties constitute 48% and 38%, respectively, of the olives used for oil production in Cyprus, accompanied by such other varieties as the Manzalino, Morayolo, and Picual. The results of the first stage of the survey were mapped using a GIS mapping tool, and subsequently inputted into a more generic tool (i.e. Google Earth), for easy sharing of information with other users (Figure 1). In Figure 1, all olive mills currently in operation in Cyprus are indicated, while the eight mills that were selected for the second stage of the survey are indicated with a larger size balloon. Aside from the location of each mill on the island, meteorological, geological, and operational information for each location have been included in the database produced. Table 1 provides an example of the type of information included in the GIS-based database, focusing on eight mills selected for the second-stage of the survey. Figure 1. Map of Cyprus illustrating the location of the 26 olive mills. (The 8 mills selected for the second stage of the survey are indicated with a larger size balloon). 3 METHODOLOGY 3.1 Identification of Sampling Locations After identifying the officially-registered olive mills throughout the island, a questionnaire was developed which was used in a series of personal interviews with owners of the olive mills. Data from only 25 (out of 26) olive mills was collected due to the refusal of one of the mill-owners to participate in the survey. The methodology followed for the selection of olive mills took into consideration the factors which may affect the composition of OMWW qualitatively and quantitatively. According to Niaounakis and Halvadakis (2004), these factors include: cultivation soil, harvesting time, degree of ripening, olive variety, climatic conditions, use of pesticides and fertilizers, duration of aging and employed olive oil extraction process. For purposes of this study 8 olive mills were identified and sampled, and their wastewaters were analyzed in the Environmental Engineering Laboratory of Frederick University. The selection of the 8 sampling locations was based on factors that are considered as more important in contributing certain character to the olive oil and the mill wastewater. These factors were the climatic conditions (local meteorology), the cultivation soil (i.e. geology of the area), the olive variety and the extraction process. The eight selected olive mills from which samples were taken, analysed and used for spatial and temporal characterization of OMWW in Cyprus are presented in Table 1. Climatic conditions such as temperature, precipitation, humidity were gathered from the nearest meteorological station (Meteorological Survey, 2011) of each olive mill while a digital geological map of Cyprus (Geological Survey Department, 2011) was used to identify the predominant geologic formation of the area surrounding each olive mill. Table 1 - Sample data included for each olive mill in operation in Cyprus. (Sample data shown for a selection of eight mills that were sampled for the second stage of the survey). Wastewater Average Olive Mill Olive Extraction produced Rainfall Geology Location variety (m3/year) (mm) Avgorou, 1 3-Phase 1450 339 Circum Troodos Koroneiki Famagusta Evrychou, 2 3-Phase 4333 853 Combination Kipriaki Nicosia Orounta, Koroneiki & 3 3-Phase 2233 297 Circum Troodos Nicosia Kipriaki Timi, 4 3-Phase 2417 380 Combination Kipriaki Paphos Ora, 5 2-Phase 1267 519 Troodos Terrain Koroneiki Larnaca Lythrodontas, 6 3-Phase 2917 451 Troodos Terrain Kipriaki Nicosia Choirokoitia, 7 3-Phase 3083 375 Circum Troodos Koroneiki Larnaca Ypsonas, 8 3-Phase 1500 453 Circum Troodos Koroneiki Limassol 3.2 OMWW Sampling Procedure Triplicate samples of OMWW were collected four times from each identified site during the olive processing season. The olives harvesting season, for Cyprus, normally spans the months of October to March. Samples for the survey were collected in the middle of November, December, January, and February. The samples were taken from the central storage tank of wastewater for each mill (i.e. common collection point of wastewater before being dispatched to the evaporation ponds) thus resulting in capturing the character of the mixed liquid waste stream of each olive mill. A strict protocol was followed, avoiding sampling from the bottoms of storage tanks which could alter the representativeness of analysis results due to settled solids or contaminant build- up. Samples were taken from the mid-point of storage tanks, away from its walls, and during times when tanks were full. Samples were collected with specially devised grabs, stored in screw-cap polyethylene bottles, tightly closed, and immediately transported, in a chilled cold box, to the Environmental Engineering Laboratory of Frederick University, in Nicosia. Upon arrival to the laboratory samples were frozen to -20°C, and stored as such until chemical analysis. 3.3 Laboratory Analysis of Physicochemical Parameters OMWW samples were analyzed for nitrogen and phosphorus content, chemical oxygen demand (COD), biochemical oxygen demand (BOD), pH, total phenolic content, color, total suspended solids (TSS), and total solids (TS).