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Closed wastewater cycle in a meat producing and processing industry T. Manios a,*, E. Gaki b, S. Banou b, A. Klimathianou b, N. Abramakis b, N. Sakkas c a

School of Agricultural Technology, Technological and Educational Institute of Crete, Heraklion 71500, Crete, Greece

b

Department of Natural Resources Engineering, Technological and Educational Institute of Crete, Halepa 73133, Chania, Crete, Greece

c

Laboratory of Environmental Informatics, Technological and Educational Institute of Crete, Stavromenos 71500, Heraklion, Crete, Greece Received 25 July 2002; accepted 6 December 2002

Abstract Creta Farm Plc, owns the largest meat producing (pigs rearing), processing and packaging unit in the island of Crete, in Greece, placed outside the city of Rethymnon in the north coast of the island. From the farm, where more than 20 000 pigs of various ages and sizes live, 300
/ 320 m3 of wastewater are collected in a daily basis. From the slaughterhouse and the processing unit another 100
/125 m3/d are produced. The wastewater treatment system is a combination of settling and aeration tanks, with decanters operating in different phases of the process, mainly for the removal of the solids from the wastewater. The average biochemical oxygen demand and total suspend solids values of the treated effluent are 40 and 80 mg/l respectively. From this, almost secondary treated, effluent about 100 m3 are used for cleaning the sewage pipes of the rearing unit (animals houses). The remaining 300 m3 are disinfected with a weak chlorine solution before used for irrigating trees, grass and various other plants. More than 2000 eucalyptus trees, 1500 tamarix trees and a large number of olive trees are growing in the site creating a pleasant view and at the same time help minimising the odour problem. # 2003 Elsevier Science B.V. All rights reserved.

* Corresponding author. Tel.: /30-810-379-400; fax: /30-810-318-204. E-mail address: [email protected] (T. Manios). 0921-3449/02/$ - see front matter # 2003 Elsevier Science B.V. All rights reserved. PII: S 0 9 2 1 - 3 4 4 9 ( 0 2 ) 0 0 1 6 9 - 6

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Keywords: Pigs rearing; Farm; Slaughterhouse; Meat processing; Wastewater; Treatment; Reuse; Closed wastewater cycle

1. Introduction Current legislation demands the treatment of wastewater, industrial and domestic, in order to meet effluent quality standards set by environmental authorities. This has forced many industries to treat their wastewater to the level obtainable by the best available technology for wastewater treatment. Where extensive treatment of wastewater is necessary to meet stringent discharge permits, the quality of the treated effluent often approaches that of freshwater streams and should be considered a valuable water resource, particularly where water is scarce (Chartzoulakis et al., 2001). Regulatory agencies encourage utilisation of such treated effluents for non-potable uses in general, and for irrigation in particular (Abou-Elela et al., 1995; Hamoda and Al-Awadi, 1995). High quality wastewater treatment imposes a large cost on companies, forcing them to investigate alternatives, which will satisfy the legislation requirements while at the same time requiring the lowest investment and operational cost. A solution to the problem, of increasing popularity, is the treatment of the industrial wastewater and its reuse in a number of different applications in the limits of the industry itself. Companies are using their treated or partially treated wastewater for cooling water, flushing toilets water or irrigation of plants and grass growing in the site (Sastry and Sundaramoorthy, 1996; Willers et al., 1999; Hien et al., 1999). It is not uncommon for industries to reuse domestic wastewater as presented in Kurbiel et al. (1996). This practice allows the industries to reduce substantially both the treatment cost and the quantities of fresh water needed on the site. The aim of this paper is to present a case study of an industrial unit owned by Creta Farm Plc, in the island of Crete in Greece, applying this closed wastewater cycle. This case study is of high interest for a number of reasons: (a) Crete, in the southern edge of Europe, is challenged by inadequate water resources, especially in summer where more than 3 000 000 tourists visit the island, (b) this closed water cycle is one of the first ever applied in Greece, where the idea of water reuse generally encounters strong objections from the public, (c) this is a meat producing and processing industry with an excellent health and safety record which proves that well designed wastewater systems can guarantee the safe reuse for workers, animals and consumers, and (d) Creta Farm Plc is one of the faster growing domestic companies, aiming in investing in a new industrial unit in Central Greece, in which the same idea of closed wastewater cycle will be applied, this time for the irrigation of poplar trees for the commercial production of high quality timber.

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2. Creta farm: history and financial profile The company begun in 1970 and its main objective was the production and packaging of preserved foods and vine leaves that were exported. The piggery unit was established in 1971 and since 1985 the company’s activities included the production of cooked pork meat from their privately owned slaughterhouse. In 1995 the company was named as ‘Creta Farm’. Profits and turnovers have been increasing steadily for the past 8 years (Fig. 1). Creta Farm took over another four companies that also work with delicatessen (Hellas Farm, Eurocreta, Creta Mercantile and Teto Farm) and became one of the top three delicatessen companies and the first proliferating delicatessen company in Greece. Its share in the Greek delicatessen market is now above 10%. Creta Farm works only with pork meat. The company was introduced in the Greek stock market in April 2000 and drafted more than fifteen million Euro (t). Creta Farm Plc applies HACCP in all the sectors of its production. The application of Hazard Analysis is the way of checking the safety of every product for the consumer. From 1999, ISO 9001 is applied to ‘development, production, storage, sale of delicatessen and concoctions of meat’ and ISO 9002 is applied to ‘development, procreation, fattening and slaughter of pigs that feed on special breeding (feeding exclusively with vegetative origin forage and fattening without the use of antibiotics)’. The specific ISO 9002 is awarded to only a few companies in Europe and Creta Farm is the only Greek company. From early 2000 Creta Farm applied ISO 14000, for environmental management.

3. The wastewater collection, treatment and reuse system Fig. 2 presents a layout of the wastewater collection, treating and reusing system. There are more than 5000 m of sewage pipes for the collection and transportation of the wastewater from the various inlets in to the treating system. The actual wastewater treatment systems covers an area of 7000 m2, containing settling and

Fig. 1. Profits and turnovers since 1996 in thousand t.

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Fig. 2. Wastewater treatment layout (secondary treated wastewater, disinfected wastewater)

aeration tanks, decanters and a disinfection unit (chlorination). The wastewater flowing from the farm and the slaughterhouse/packaging/processing unit is treated, up to a point, separately. This is due to the construction of the various parts of the site at different periods. In the pig rearing farm, more than 20 000 animals of different ages and sizes, produce on a daily basis approximately 65 m3 of mixed wastewater (10% solids). The animal housing consists of 16 corridor shaped independent buildings (approximately 100 m long and 10 m wide), the floor of which is constructed in such way that all animal extracts fall directly on to a collection ditch. In a weekly basis the floor and the collection ditch of each house is cleaned using potable quality water. This practice adds another 100
/120 m3 of wastewater in the above mentioned 65 m3 in a daily basis. This ‘mixture’ flows through an extensive sewage pipe network,

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frequently cleaned with the help of 20
/40 m3/d of fresh water and 100 m3/d secondary treated
/recycled wastewater. In total 300
/320 m3/d of wastewater is produced in the farm. The wastewater from all the different houses in the farm is collected in a covered tank (Fig. 2, Primary Collection Tank), which also operates as a fat removal unit. The retention time in the tank varies from few hours to a maximum of 1 day. In this tank a large portion of the fat is removed through floatation, where the remaining wastewater is pumped from the bottom into a settling tank. In the entrance of the settling tank, part of the solids is removed by three mechanical separators (decanters). Approximately 10
/15 m3 per week of sludge is collected through these decanters, 80% of which is moisture. The sedimentation tank (Fig. 2), built by reinforced concrete and covered by a windproof net, has a total volume of 160 m3. This produces an average hydraulic retention time of 12 h, which compared to that of a municipal sedimentation tank is more than double. In this tank both floatation and sedimentation are allowed. The overflow effluent (after fat removal) is introduced into three rectangular aeration tanks, equipped with surface agitators, where the sediment is forwarded in an anaerobic digestion tank, with a total volume of 1400 m3. Daily, 140 m3 are pumped from the bottom of the anaerobic tank into two centrifugally operating drainers. The liquid from the centrifugation is forward to the first of the rectangular aeration tanks, while the solids are removed regularly as sludge (5
/10 m3/week). Up to this point (in the entrance of the three rectangular aeration tanks) the wastewater from the farm should be considered as primary treated with solids removal above 50% and a 5 day biochemical oxygen demand (BOD5) reduction up to 30
/35%. The wastewater produced in the slaughterhouse and the meat processing and packaging site (approximately 100
/125 m3/d), is introduced to a small collection tank and then forwarded to a balancing tank, in which a large portion of the fat is removed through floatation. The hydraulic retention time in this tank is approximately 12 h. From the balancing tank the wastewater is pumped into a triangular aeration tank, also equipped with a surface agitator. The characteristically red effluent of the triangular tank (from the animals’ blood), ends up in the largest of the rectangular aeration tanks, with a total volume of 650 m3. At the exit of the triangular aeration tank the wastewater from the processing/packaging unit and the slaughterhouse should be considered also as secondary treated with a solids reduction above 50% (solids original concentration in this wastewater stream is far smaller than that from the farm) and a BOD5 reduction above 50%. The three rectangular aeration tanks (all three using surface agitators) are responsible for removing an average 30
/40% BOD5 from the wastewater. The reason why one of the tanks is double the size of the other two has to do with the fact that this tank treats part (1/3) of the wastewater from the farm and all the wastewater from the other parts of the site. Also this is the only tank in which is recycled part of the sludge removed by the decanters treating the effluent of all three rectangular tanks. This practice, which is considerably similar to the activated sludge practice, helps improve the performance of the largest aerated rectangular tank. The decanters produce no more than 5
/10 m3/week of sludge, which when added to the sludge

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Fig. 3. Year fluctuation of BOD5 concentration in the secondary effluent.

produced in other parts of the treating system reaches an average of 25
/30 m3/week. The effluent exiting these decanters should be considered as secondary treated effluent. A number of different parameters were used for the evaluation of the wastewater treatment system’s performance, through monthly sampling and analysis of this effluent. Figs. 3
/5 presents the results from these analysis for BOD5, chemical oxygen demand (COD) and total suspend solids (TSS), respectively.

Fig. 4. Year fluctuation of COD concentration in the secondary effluent.

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Fig. 5. Year fluctuation of TSS concentration in the secondary effluent.

About 300 m3 from the secondary treated wastewater, will be forwarded to the irrigation collection tank. Before entering the tank a weak chlorinated solution will be used in order to reduce the number of the remaining pathogenic microorganisms to a non-detectable level. The remaining 100 m3 will be collected in another tank from which will be pumped daily for cleaning up the sewage collection pipes attached to the animals house. In the farm 2000 eucalyptus saplings were planted almost 4 years ago and have already reached a height of 4
/6 m. The planting continued with the tamarix saplings

Fig. 6. Year fluctuation of EC value in the final effluent.

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that come up to 1500 and are 100 more to be planted for the gradual coverage of all available space in the farm. Fig. 6 presents the electrical conductivity (EC) of the wastewater in the final collection tank and just before being pumped for irrigation. There is an extensive pipe network (more than 10 000 m) distributing the wastewater for the watering of the plants; mostly a drip system is used. The disposal of liquids in the ground is being programmed year round, except from the days with intense rainfall or when the system is maintained, an estimated total of 20
/25 days annually. During these days the wastewater remains in the storage tanks. This management is because of the hot
/dry climate of the area and the need to satisfy the absorbing ability of the farm’s sandy clay soil. Such soils have a percolation rate of 3.5 mm/h, which allows the disposal of 84 m3 of wastewater per day/1000 m2. A dry period of 15 days, between irrigation of the same area, has been applied in order to reduce any potential environmental risk. Additionally to the treated wastewater (102 000 m3/year) a total of 25 000 m3/year of fresh water will also used for the irrigation of the plants. Based on the above assumptions the minimum necessary area for a safe disposal of the irrigation water (a total of 125 000 m3/year) is about 66 000 m2. The area irrigated in Rethymnon is about 93 000 m2, far larger than the required. All the wastewater analyses were performed by a private Water and Wastewater Analysis Laboratory, with which Creta Farm Plc has a constant collaboration. In all analyses the Standard Methods for the Examination of Water and Wastewater (APHA, 1995) have been used.

4. Discussion In the Rethymnon site of Creta Farm Plc, a maximum 450 m3 of wastewater are produced on a daily basis. This amount is equivalent to that produced by a small town of 2500 people (Tchobanoglous and Burton, 1996). If the treated wastewater was used in any ‘Non Food Crop’ outside the boundaries of the company’s site then the level of treatment should be increased in order to produce a steady BOD5 and TSS value of less than 30 mg/l, with the faecal coliform count under the 200 cfu/100 ml boundary (EPA, 1992). If the wastewater was to be reused for landscape irrigation then the guidelines are more stringent, with a BOD5 value of less than 10 mg/l and no detectable pathogens. These strict limits for landscape irrigation are based on the facts: (a) in such facilities people come in direct contact with the irrigated land and plants (grass) just a few hours after the wastewater application, and (b) sometimes spraying systems are used which could allow the dispersion of pathogens in a substantial distance from the application point (Angelakis et al., 2001). This is not the case in Creta Farm’s site in Rethymnon. Surface irrigation has been used (dripping system) and all trees and bushes, watered with the reused wastewater, are in restricted areas not easily accessible by personnel or visitors, increasing the safety level undertaken by the company. According to Figs. 2
/4, the level of wastewater treatment could be consider close to secondary. The average BOD5 value is slightly above 40 mg/l (COD of 160 mg/l),

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where the average TSS concentration is above 80 mg/l. Chlorine is used for the disinfection of the irrigation wastewater, an application which should be considered adequate in order to reduce the number of faecal coliforms to a non-detectable level. The use of surface irrigation, the small amount of wastewater applied per surface m2, the weather conditions (elevated temperatures all year) and the geological characteristics (limestone formations) allows us to assume that there is no danger for the ground water, which exists at a considerable depth (approximately 60 m) (Tchobanoglous and Burton, 1996). There is a considerable number of different Eucalyptus varieties, growing in Crete with E. camaldulensis being the one growing in the site. One of the most important characteristics of this specific variety is its increased salt tolerance in both the irrigation water and the soil (Niknam and McComb, 1999). This is of great importance due to the high EC value of the reused wastewater (Fig. 6). The effect of the continued application of this low quality treated wastewater on the soil was not determined, it should however be evaluated and some precautions should be taken. The danger of increasing salinity and creating a substantial problem for the plants is clear and present as long as the company is not taking any measures to improve the effluent quality. This, however, should be considered as the only danger for the environment from this practice. The use of low quality treated wastewater for plant irrigation as it takes place in Creta Farm Plc, could be considered as part of the treating process. Actually there is no significant difference between this closed wastewater cycle and a slow application rate natural system where partially treated wastewater is used for biomass development (Tchobanoglous and Burton, 1996). This practice of reusing, in a closed wastewater cycle, industrial wastewater has been applied in a number of companies, world wide. In all applications, similar to the Creta Farm example, the level of treatment is lower than secondary, which is suggested by both EPA (1992), WHO (1989) guidelines, for landscape irrigation. Willers et al., (1999) suggested that partially treated wastewater could be used for alternative purposes as for example grass irrigation and manure flushing in the animals’ housing. Creta Farm, in which no antibiotics are used in the animals growth, does not incorporate this practice. However, it uses part of the wastewater for flushing sediments and solids from the sewage pipe lines where no contact between animals and water takes place. Hien et al. (1999) presented similar data from a tapioca industry in Vietnam where, partially treated wastewater was used for either irrigation purposes or cleaning part of the factory and equipment. The implementation of the closed water system in the Rethymnon site helped the company reduce its operational cost, by lowering its need for fresh water for plant irrigation and cleaning off sediments in the sewage pipes. The most substantial cost reduction however, is achieved through the operation of a wastewater treatment system which produces a lower quality effluent than that required if the wastewater was disposed in surface water or reused for crops or landscape irrigation, outside the company’s limits. It is estimated that improving the wastewater system in order to reach the above mentioned limits should require an additional investment of at least 250 000t. Is also

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estimated that this expansion of the wastewater system will require an additional one or two workers, increasing almost by 50% the number of people working in the site at this moment. These costs and the fact that as the system operates at the moment with no problems encountered from either the legislation or the local authorities, provides the company a good enough excuse to retain this practice as it is. The choice of Eucalyptus was not based entirely in its tolerance in salinity. Eucalyptus trees are fast growing with the ability of accumulating from the irrigating wastewater substantial amounts of nutrients (Guo and Sims, 2000; Heaton et al., 2002). Are also very well adapted to the local environment and soil, which would increase the success rate of the planted seedlings.

5. Conclusions Based in the above facts is safe to suggest that environmentally speaking the company has undertaken all the necessary precautions which will allow adequate treatment of the produced wastewater, the minimisation of the environmental impact of the site and the reduction in fresh water needs. The company saves considerable funds by operating a partially secondary wastewater treatment system since no effluent is leaving the company boundaries and the ground water is under of no contamination threat. Plants are well developed, producing a pleasant site and at the same time creating a natural fence around the farm, reducing any odour dispersion. The possible salinity problem is under investigation with extensive soil sampling for analyses. A potential expansion of the wastewater treating system with the addition of a constructed wetland is also considered by the company. Creta Farm Plc regards this practice as successful and is planning implementing the same pattern in its new site in Trikala (Central Greece) where more than 80 000 pigs will be sheltered. The produced wastewater will be used for the irrigation of poplar trees for the production of high quality commercial timber. The wastewater treatment in this new site will be a state of the art system which eventually (and hopefully) will produce an effluent with far less EC than that of the Rethymnon site. The company is also planning to construct in Trikala a sludge and green waste cocomposting unit for the production of high quality horticulture mixtures.

Acknowledgements We would like to thank the Chairman of the Board E. Domazakis and the General Manager K. Domazakis for releasing all the necessary data, as also their personal interest in the project. We would also like to express our gratitude to N. Tolika for his daily involvement with this project and his effort to answer all questions raised.

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References Abou-Elela SI, El-Kamah EM, Aly HI. Management of wastewater from fertiliser industry. Water Sci Technol 1995;32:45
/54. Angelakis AN, Tsagarakis KP, Salgot M, Marecos do Monte MHF, Dialynas G. Advanced wastewater treatment and reuse: design, operation and maintenance. Heraklion, Crete, Greece: National Agricultural Research Foundation, 2001. APHA, Standard methods: for the examination of water and wastewater. Washington DC: Published jointly by: American Public Health Association, American Water Works Association, Water Environment Federation. 19th ed.; 1995. Chartzoulakis KS, Paranychinakis NV, Angelakis AN. Water resources management in the island of Crete, Greece with emphasis on the agricultural use. Water Policy 2001;3:193
/205. EPA, 1992. Guidelines for Water Reuse, EPA/625/R-92/004, USA. Guo LB, Sims REH. Effect of meat works effluent irrigation on soil, tree biomass production and nutrient uptake in Eucalyptus globulus seedlings in growth cabinets. Bioresource Technol 2000;72:243
/51. Hamoda MF, Al-Awadi SM. Wastewater management in a dairy farm. Water Sci Technol 1995;32:45
/54. Heaton RJ, Sims REH, Tungcul RO. The root growth of Salix uiminalis and Eucalyptus nitens in response to dairy farm pond effluent irrigation. Bioresource Technol 2002;81:1
/6. Hien PG, Oanh LTK, Viet NT, Lettinga G. Closed wastewater system in the tapioca industry in Vietnam. Water Sci Technol 1999;39:89
/96. Kurbiel J, Zelgin K, Rybicki SM. Implementation of the Cracow municipal wastewater reclamation system for industrial water reuse. Desalination 1996;106:183
/93. Niknam SR, McComb J. Salt tolerance screening of selected Australian woody species */a review. Forest Ecol Manag 1999;139:1
/19. Sastry CA, Sundaramoorthy S. Industrial use of fresh water vis-a`-vis reclaimed municipal wastewater in Madras, India. Desalination 1996;106:443
/8. Tchobanoglous G, Burton FL. Wastewater engineering: treatment, disposal and reuse, 3rd ed.. Metcalf & Eddy, Inc, 1996. Willers HC, Karamanlis XN, Schulte DD. Potential of closed water systems on dairy farms. Water Sci Technol 1999;39:113
/9. WHO, Health guidelines for the use of wastewater in agriculture and aquaculture. Geneva: World Health Organization, Technical Report Series; 778, 1989.