A Combined Leachate And Industrial Type Of Effluents That Treatment Plant: The Case Of The Wastewater Treatment Plant At Marathounta Landfill In Cyprus

A COMBINED LEACHATE AND INDUSTRIAL TYPE OF EFFLUENTS that TREATMENT PLANT: THE CASE OF THE WASTEWATER TREATMENT PLANT AT MARATHOUNTA LANDFILL IN CYPRUS T. LOLOS, C. TSOMPANIDIS, G. LOLOS, G. TAVOULARIS AND C. RAPTIS * ENVIROPLAN S.A., 40, Ag. Konstantinou St., “Aethrio” Business Center 15124, Athens, Greece

SUMMARY: The Marathounda landfill in Pafos is the first site constructed in Cyprus in 2004 conforms to the Landfill Directive 99/31. Initially, a dedicated biological treatment plant was envisaged on site for treatment of the generated leachate. During the construction phase, an upgrade of the plant was discussed among the competent authorities, in order to cope with effluents from other sources, mainly industrial. Indeed, Cyprus relies heavily on agriculture and tourism and small wastewater quantities from many sources of the two main economic activities are generated. This upgrade deemed eventually necessary in order to receive additionally a range of industrial type effluents, such as: wineries, slaughter houses, dairies, car laundries, grease and fat, as well as raw sewage and dewatered sludges from municipal WWTP. 1. INTRODUCTION In Cyprus, not all rural areas are connected to a sewerage system and still rely on a combination of cesspools emptied by trucks. Also, industrial facilities have a rather small size, where a dedicated treatment plant is not economically viable. The present paper describes a successful example of a combined leachate and industrial WWTP, aiming to terminate the dumping of polluted by-products into the soil. The treatment at the Marathounda WWTP consists of the following discrete stages: ƒ Reception and inspection ƒ Pre-treatment of liquid effluents and sludges ƒ Biological treatment ƒ Tertiary treatment ƒ Sludge dewatering The modified design had to take into account the heavily fluctuating seasonal hydraulic and organic load and the adequate pretreatment before the biological stage. In accordance with the literature providing evidende that a Sequential Batch Reactor (SBR) is the most suitable technology for industrial wastewaters, an SBR type of extended aeration biological system has been chosen. In this, microorganisms with a strong resistance to ammonia

Proceedings Sardinia 2009, Twelfth International Waste Management and Landfill Symposium S. Margherita di Pula, Cagliari, Italy; 5 - 9 October 2009 © 2009 by CISA, Environmental Sanitary Engineering Centre, Italy

and other inhibiting compounds are cultivated. A Dissolved Air Flotation unit has been selected as the preferable pre-treatment stage. The selection of the electromechanical equipment is based on the fitness for purpose, safety, reliability, maintainability and availability of spares and services. All pipelines were stainless steel.

2. DESCRIPTION OF THE WASTEWATER TREATMENT PLANT 2.1 Reception and inspection of tankers The tankers that enter the plant are registered at the entrance of the landfill site. They are weighed and recorded in the database. The initial record of the tankers is done at the entrance/guard house/weighing station of the WWTP from the personnel that service the refuse tracks. At the entrance, suitable information is given for the emptying point of the tanker accordingly to the type of the effluent and the standardised typescript form completed by the driver of the tanker at the collection of the effluents. The form include basic elements for the effluents like volume estimation, elements of origin of the liquid effluents (e.g. industry, hotel, restaurant or houses etc) and other information necessary for the further treatment of the liquid effluents. The confirmation of the recognition via the automatic system and the demonstration of the completed form constitute the first stage of inspection of the tanker. After the weighing station the tanker is directed with suitable identification to the reception installations of the liquid effluents brought to the station where the second analytical inspection is carried out after the receipt of the standardized typescript form and before the emptying in the predetermined point. It is intentional that a more essential second inspection is done close to the emptying space of the liquid effluents so that the delay at the guard house-weighing station is avoided since it services the refuse tracks as well. During the start-up of the operation of the plant as well as following this stage occasionally a sampling and chemical analysis of the liquid effluents brought is carried out for the confirmation of the suitability for their treatment. The sampling is done preliminary with a rapid examination of the basic parameters of the effluents brought which are the pH, redox potential, conductivity and perhaps biotoxicity (rapid toxicity test e.g. Microtox type). With the rapid inspection at the initial stage of the plant operation a sample of two litres approximately is taken for further analytical inspection. During the first stage of the plant operation and until the complete development of capable biomass, the inspections is done in every tanker so that toxicity phenomena in the microorganisms is avoided and in parallel the completion of the data base is done for the industries serviced at the area which it include the basic determination of the load of the liquid effluent from each one. The results from the preliminary inspection are completed in the standardized form and if the basic reception specifications are met, a permit is given by the manager of the plant for the emptying of the effluents. In the case of one unsuitable effluent, the keg is directed in the special emptying point for the temporal storage of the effluent (non-conforming liquids tank). After this, regulated feeding of this effluent is carried out in the plant to minimise the negative effects in the process of the plant. The inspection for the correct position of emptying the tankers, the information to the drivers and the sampling is done by the assistant manager of the plant. The rapid inspection is done by the manager of the plant while the analytical inspections will be done in collaboration with the suitable personnel for the operation of the landfill site.

2.2 Pre-treatment of liquid effluents and sludges The pre-treatment of the liquid effluents and especially the sludges that will end up for treatment in the biological plant of the Marathounta WWTP is regarded as necessary for the following reasons: ƒ removal of large solids; ƒ restrain of inert solids; ƒ removal of oils and grease; ƒ restrain and sedimentation of the organic solids; ƒ thickening of low-solid concentrated sludges. After the reception, record and inspection of the effluents from the personnel of the station, the effluents is carried in the 1st balancing tank. The liquid effluents which come from grease collectors, car and laundry wash go through automatic grate unit for sand and grit removal before they end up in balancing tank A. The sludges from the biological treatment of the effluents and the liquid effluents of the slaughter houses, wineries and dairies as well as the effluents from the buildings of the landfill site also end up in balancing tank A directly with the by-pass of the pretreatment stage. For the case where the sludges of biological treatments have already been thickened, it is possible for feeding them directly to the sludge holding tank. Balancing tank A gives the opportunity of homogenizing the effluent characteristics and specifically the sludges with a continuous mixing as well as flowrate control towards Dissolved Air Flotation treatment that follows. Ahead of the Flotation unit a blender allows sufficient contact time of the effluents from balancing tank A with the coagulant and flocculant. The chemicals is introduced with automatic dosing systems and optimize the efficiency of the flotation process. The floation unit intend to separate the suspended solids and fats, oils, greases (FOG) from the effluents. With this method, the pollution load of the effluents is reduced greatly. The operation of the unit is based on the capability of dispersion of air bubbles at the bottom of the tank where they come in contact with the effluents and they attach on the suspended solids leading them to the surface of the tank. The treated liquids, having low content of solids, are directed with gravity to balancing tank B. This tank gives the opportunity to balance the characteristics of the effluents with continuous mixing as well as t as well as flowrate control towards to the biological treatment units that follow. The total volume of the balancing tanks before the biological treatment will be sufficient for smooth introduction the biological treatment. 2.3 Aerobic biological treatment The aerobic systems of intermittent feed (Sequencing Batch Reactor - SBR) were the forerunner systems of the activated sludge at the initial steps of the treatment of the liquid effluents. The SBR systems are applied extensively to the strong industrial effluents including the drains from the landfill sites as well as to the installations of effluents treatment replacing the conventional methods with aeration tanks and settlement tanks with excellent results. The improvements of the recent ten years in the automation systems (Programmable Logical Controller – PLC) and the measurements in combination with the international experience from intermittent feed systems of large sizes gave a new push in the application of the reactors of SBR type. The most significant advantage of the SBR type reactors is the flexibility and the capability adaptation of the system in every treatment demand in the vigorously changing loads and the development of an especially adapted biomass capable to treat especially difficult liquid effluents including the landfill site drains. The SBR reactors have the capability to work as anoxic for denitrification and phosphorous

removal, as oxygenated for the oxidation of the organic load and finally as clarifying tanks for the restrain of the biological sludge. Additionally the SBR type reactors due to the development of adapted biomass have the capability of operational adjustment of especially large range and are necessary for the effluent treatment which contain high concentration of nitrogen and come from anaerobic conditions (landfill site drains, cesspool sewage, anaerobic treatment etc). The aerobic biological treatment is designed to ensure the removal of biodegradable organic pollutants that are in the effluent achieving thus the quality levels asked in the treated effluents. The treatment procedure is based on the SBR reactor technology which is a variation of the activated sludge process. Due to the fact that the SBR reactor will operate with sequence of the treatment phases, it will achieve during one operational cycle the best output in the removal of the pollutants, giving at the same time the capability of fluctuation based on time of the various phases of the operation maximising the output of the separate stages. For operational flexibility reasons of the aerobic biological treatment unit, it is developed in two parallel equivalent treatment lines. The untreated effluent is directed in the adapted biomass which stays in the reactor continuously since in this reactor the process of biomass subsidence is done also. The ratio of the organic pollutant to the biomass is the key factor for the reactor to achieve the quality asked for the treated effluent. Since only one small percentage of excess sludge is discharged during every cycle, the quality of the biomass is unchanged. The process of the aerobic treatment will follow the below stages: ƒ Fill / Treatment ƒ Main treatment ƒ Sedimentation / Separation ƒ Removal of treated effluents / Excess sludge The mixing of the reactor’s contents is achieved with the use of submerged mixer. This way anaerobic and anoxic conditions is achieved something that obstructs the development of filamentous microorganisms; essential conditions for the removal of the nitrogen (dentitrification). The operation also is possible under simultaneous aeration of the wastewater for the treatment of especially high organic load. The selection of the stages provides the possibility of substantial help of anoxic conditions. Furthermore, intermittent operation of the aeration blowers during the low flow or low organic load is possible. With the fill of the reactor, the complete treatment of effluent start. The treatment under aeration is continuous or intermittent with the aim to maximise the output of the nitrification/denitrification cycles. In the stage of sedimentation / separation the mixing/aeeration steps be interrupted in order to restore calm conditions in the tank and to achieve the separation of solids from the treated drains. After the completion of the biomass separation stage from the treated effluents, which has duration of 30 minutes, a part of the reactor’s volume is transferred via a floating decanter (with a submersible pump) into the chlorination tank which also act as an equalisation ahead of the tertiary treatament. The excess sludge is removed during each cycle and is transferred in the sludge holding tank. The removal of the excess biological sludge is done after the discharge of the treated water or simultaneously. After the completion of the treated water discharge phase and the removal of the excess sludge, the reactor is ready to accept the next batch of effluent. 2.4 Tertiary treatment 2.4.1 Filters of sand/ Carbon Chlorinated water is pumped the pressurised multilayer sand filters. After the sand filters, an activated carbon filter is installed for the restrain of large-molecular organic compounds which are not biodegradable. The filters effluent end up by gravity in the filter effluent collection tank

or the irrigation tank. 2.4.2 Chlorination tank / Equalization Tank The SBR treated effluent is discharged in this tank where disinfectant is added for the reduction of pathogen microorganisms. The filter feed pumps will draw from this tank. Calcium Hypochlorite solution (3-5%) is used for disinfection. 2.4.3 Irrigation / Recycling tank From the filtering stage the treated effluents end up in the filter effluent collection tank or the irrigation tank. It should be mentioned that after the above treatment the treated effluents can be disposed for irrigation if they are within the regulations for unrestricted irrigation. Due to the expected high conductivity of the wastewater, the disposal of the treated effluents for long time into a limited space is very possible to create salinity problems of the ground. For the tackling of this case an installation of reverse osmosis unit will be provided with the aim to treat further the already biologically treated effluents and truly maintain unrestricted irrigation regulatorylimits. 2.4.4 Reverse osmosis unit The biologically treated effluents still possess high conductivity values, since leachates have high salinity. In this respect, a reverse osmosis was installed for salinitiny removal. From the exit of the filter of activated carbon and before the irrigation tank, the treated water is fed to a reverse osmosis unit of a capacity of 220 cubic meters per day. The product of the reverse osmosis which expected to be approximately 165 cubic meters per day end up nto the irrigation tank and its overflow is directed in the nearest superficial receiver while the produced brine which is approximately 55 cubic meters per day is recycled to the landfill site via the recycling network. The frequency of operation of the osmosis is determined based on frequent conductivity measurements in the disinfection unit. The special energy consumption for the osmosis of the treated liquid effluents with the relatively low salt content is low in the level of 1,2 kwh per m³. For the protection of the membranes from the salt disposition and possible development of microorganisms on their surfaces suitable quantities of anti-scale and dechlorination chemicals is dosed and before the RO unit an Ultra violet disinfection unit is provided. 2.5 Sludge treatment – Supporting installations The sludge treatment line is composed of a sludge holding tank and sludge dewatering assembly. The sludge produced from the flotation process and the excess biological sludge from the tanks of aerobic biological treatment (SBR) end up in the sludge tank. In the sludge tank with the use of submerged mixers, the homogenisation of the sludge which is necessary for the smooth operation of the dewatering is achieved. The choice of the centrifugal separator for the dewatering of the sludge contrarily to the use of a belt filter press is done mainly due to higher percentage of solids that is achieved with the centrifuge contrarily to the belt filter press but also due to significant water wash demands that the belt filter presses have. The dewatered sludge solids is gathered in a track that is used for the transfer of the sludge to the landfill site. The separated liquid created from the dewatering of the sludge returns to balancing tank B. To increase the efficiency of the dewatering process, suitable polymer solution is fed from a dosing system. The preparation of the solution as well as the collection and disposal of the dewatered sludge in the landfill site is done by the assistant manager of the plant.

2.5.4 Deodorisation system Due to the composition of the effluents, odour emission is expected from the reception assemblies, the equalisation tanks, the sludge tank and the pre-treatment and sludge dewatering places. For this reason there are two independent deodorisation units with the use activated carbon filters. The filters of activated carbon have been chosen instead of biofilters mainly due to much smaller space demand and the simpler manufacture and operation of the activated carbon filters. The above leads to the choice of the deodorisation systems with activated carbon. The frequency of replacement of the activated carbon is annually.

3. RESULTS AND DISCUSSION The design load is 230 m3/day, however most of the spring - summer period there is no rainfall and a greater amount of sewage/ industrial effluents may be accepted. From the filtering stage, the treated effluents will end up in the filter effluent collection tank or the irrigation tank. Due to the high conductivity of the wastewater, the disposal of the treated effluents for long time into a limited space is very possible to create salinity problems of the ground. For the tackling of this case an installation of reverse osmosis unit has established in order to treat further the already biologically treated effluents and truly maintain unrestricted irrigation regulatory limits.

Figure 1: Schematic process diagram of WWTP

Table 1. Wastewater loadings Parameter Loadings BOD5 (diluted) (kg/d) COD (diluted) (kg/d) Total nitrogen (kg/d) Total phosphorous (kg/d) Suspended solids (kg/d) Oil and grease (kg/d) pH (without units) Maximum supply (m³/d) Annual supply (m³/yr)

Drains of landfill site 280 600 80 1 80 1 6,5 40 7.258

Sludge of biological treatment 200 400 3 0,25 1.000 5 7 50 15.000

Liquid effluents of grease collectors 60 150 30 3 60 300 <7 30 8.250

Slaughter house sludges 21,5 64,5 1,29 0,215 86 2,15 7 4,3 1.070

Winerydairy sludges 7,5 18 0,06 0,03 60 0,3 7 3,0 450

Washing machine sludges 0,8 2,5 0,025 0,0025 87,5 0,75 6-8 2,5 620

Slaughter house sludges 5.000 15.000 300 50 20.000 500 1,2

Winerydairy sludges 2.500 6.000 20 10 20.000 100 1,2

Washing machine sludges 300 1.000 10 1 35.000 300 1,5

Cesspool sewage 180 800 25 8 800 200 7 100 30.000

Total 750 2.035 139 12 2.174 509 6-8 229,8 62.648

Table 2. Wastewater inlet concentration Entering concentrations (in mg/l) BOD5 (diluted) COD (diluted) Total nitrogen Total phosphorous Suspended solids Oil and grease Conducitivity (mS/cm)

Drains of landfill site 7.000 15.000 2.000 25 2.000 25 11

Sludge of biological treatment 4.000 8.000 60 5 20.000 100 1,5

Liquid effluents of grease collectors 2.000 5.000 1.000 100 2.000 10.000 1,2

Cesspool Average sewage value 1.800 8.000 250 80 8.000 2.000 1,5

3.263 8.856 607 54 9.458 2.216 3,1

The following Table 3 shows the WWTP Efficiency for the basic parameters in the inlet of the WWTP and after each treatment stage as well as the treated water quality at the final effluent. Table 3. Wastewater treatment plant efficiency for the basic parameters in the inlet of the WWTP and after each treatment stage Parameter Inlet Primary Secondary Tertiary Final Effluent Effluent BOD5 (mg/L) 3.263 1.131 <20 <10 negligible Suspended solids 9.458 825 <30 <10 Negligible (mg/L) Total nitrogen 607 279 <100 <10 Negligible (mg/L) Total phosphorous 54 41 <20 <10 Negligible (mg/L) Conducitivity 3.100 3.100 3.100 3.100 <1.000 (mS/cm) It should be mentioned that after the above treatments the purified water has excellent quality and is suitable for irrigation purposes of the surrounding areas while a part of the treatment water is recycling to the landfill site via a proper re-circulation network.

5. CONCLUSIONS The key issue in the design of the treatment plant is to ensure that an appropriate and costeffective system is installed, which provides for a complete and reliable solution. The use of electronic control will permit the operator and the responsible engineer to change the operation of the reactor and so to service the different demands as a function of the quality and quantity characteristics of the effluent. The ability of the operator to create aerobic, anaerobic or anoxic conditions in the reactor will contribute to the flexible operation, to the better treatment and finally to the best quality of the treated final product. The capacity of an aerobic treatment system of SBR type does not reduce the volume demand for the treatment stage since these systems are designed with the same principles of the conventional systems of activated sludge but it is increased due to the space occupied the biological sludge which in the conventional systems is maintained in sludge holding tanks. The purified water, after the above treatments, has excellent quality and is suitable for irrigation purposes of the surrounding areas while a part of the treatment water is recycling to the landfill site via a proper re-circulation network.

REFERENCES N. Artan and D. Orhon, Mechanism and Design of Sequencing Batch Reactors for Nutrient Removal, UK, IWA Publishing, 2005 Tchobanoglous G., Burton F. L., Stensel H. D., 2003, Wastewater Engineering: Treatment and Reuse Metcalf & Eddy, Inc., Fourth Ed., McGraw-Hill, Inc. Tereza Vives Fabregas, SBR Technology for wastewater treatment: suitable operational conditions for a nutrient removal, PhD Thesis, University of Girona, 20005