A VISION FOR FUTURE SLUDGE MANAGEMENT IN ALEXANDRIA ( Egypt)
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A VISION FOR FUTURE SLUDGE MANAGEMENT IN ALEXANDRIA ( Egypt)

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After full operation of secondary treatment at the East and West treatment plants, the future production of sludge from these plants and from Amriya and Agamy secondary treatment plants in addition to ...

After full operation of secondary treatment at the East and West treatment plants, the future production of sludge from these plants and from Amriya and Agamy secondary treatment plants in addition to the rest 14 secondary treatment plants all around Alexandria is expected to exceed than 1200 m3/d by 2015 thus the capacity if the sludge disposal site should exceed. Therefore, the future sewage sludge management represents a critical environmental issue in Alexandria, this management includes sludge dewatering, handling, transportation cost to the disposal sites and the final product marketing.

As the capacity of Alexandria sludge disposal system will be limited by the increase in sludge production and the current management system, there is an immediate need to investigate ways to establish a future management system and to demonstrate successful operations at higher sludge producing rates.

Currently, Site 9N the sole disposal site in Alexandria include a composting plant established when the site was initially developed as a dedicated disposal area for sludge. Consequently, land spreading of the sludge on the dedicated disposal area has ceased and all of the current production of raw sludge is now being composted using the turned windrow technique.

The present study aims to evaluate the current efficiency of the sludge management system and adopt a future vision for the Alexandria sludge system and recommend modifications to protect public health and environment.

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A VISION FOR FUTURE SLUDGE MANAGEMENT IN ALEXANDRIA ( Egypt) A VISION FOR FUTURE SLUDGE MANAGEMENT IN ALEXANDRIA ( Egypt) Document Transcript

  • A VISION FOR FUTURE SLUDGE MANAGEMENT IN ALEXANDRIA Dr. Helaly Abdel Hady Helaly (1) Chem. Hussein Mohamed Abdou Elashqar (2) Dr. Samaa Maher Abdel Aziz (3) (1) “General Manager of Industrial wastewater, Sludge and Reuse Sector, Alexandria Sanitary Drainage Company”. (2) " Manager of Landfill Composting Facilities (site 9N)". (3) “Manager of Industrial Wastewater Studies and Research Department”. Keywords: sludge production, Alexandria, future, wastewater quantities, sludge dewatering, sludge handling, sludge treatment, compost marketing. ABSTRACT After full operation of secondary treatment at the East and West treatment plants, the future production of sludge from these plants and from Amriya and Agamy secondary treatment plants in addition to the rest 14 secondary treatment plants all around Alexandria is expected to exceed than 1200 m3/d by 2015 thus the capacity of the sludge disposal site should exceed. Therefore, the future sewage sludge management represents a critical environmental issue in Alexandria, this management includes sludge dewatering, handling, transportation cost to the disposal sites and the final product marketing. As the capacity of Alexandria sludge disposal system will be limited by the increase in sludge production and the current management system, there is an immediate need to investigate ways to establish a future management system and to demonstrate successful operations at higher sludge producing rates. Currently, Site 9N the sole disposal site in Alexandria include a composting plant established when the site was initially developed as a dedicated disposal area for sludge. Consequently, land spreading of the sludge on the dedicated disposal area has ceased and all of the current production of raw sludge is now being composted using the turned windrow technique. The present study aims to evaluate the current efficiency of the sludge management system and adopt a future vision for the Alexandria sludge system and recommend modifications to protect public health and environment.
  • Introduction Alexandria is the second largest main city in Egypt. It is the primary port home for 40% of Egypt industrial base. In 1998, Alexandria population was 3.5 million and it is estimated to reach 8 millions by year the 2030. Alexandria has attracted considerable attention towards developing its basic structure and overcome some of the problems facing its utilities. In the late seventies, sanitary drainage activities covered only 40% of the total inhabited area of the city. Even that the sewers were often worn out by time and unable to handle the flows they receive. The problems of streak flowing have existed due to the inability of pump stations and treatment plants to receive flows exceeding , their capacities. The city s wastewater treatment facilities which are expected to serve a population of about 4 million were not operated well and the collection system was aging and limited in coverage. These conditions lead to frequent and unavoidable operational failures which posed a direct threat to the public health, constrain industrial development, and impacted the daily lives of the residents of the city. Alexandria has two large primary treatment plants (East Treatment Plant (ETP) and West Treatment Plant (WTP). The confined capacities of 607,000 and 400,000 m3/d were respectively, sludge processing and disposal facilities (600 tons/day), collection system of large interceptors, tunnel collectors, pump stations, and establishing a site for disposing the generated scum, grit, and sludge. The implementation of wastewater project in the city of Alexandria resulted in large quantities of sludge being produced (400 tons /day) average. Future production of sludge from East and West treatment plants, Amriya and Agamy will become more than double the current production. As a result, sludge disposal site capacity has to exceed approximately 700 m3/d. This production level expected around year 2010 with only primary treatment at East and west treatment plants. The installation of a secondary treatment at the East and West treatment plants will result in the capacity of sludge site being exceeded when these units start full operation. The key features of site 9N include the composting system and the supporting facilities and equipment. Approximately 100 % of the dewatered sludge
  • and all the grit received from the treatment plants are disposed and incorporated into composting plant located in the site which is about 140 feddan. As the capacity of Alexandria sludge disposal site is limited by current operation system, there is immediate need to investigate ways to increase site capacity and to demonstrate successful operations at higher sludge producing rates. The present study aims to evaluate the current efficiencies of the ASDCO sludge disposal system with emphasis on site 9N as the main disposal facility and recommend modifications to expand its capacity and life time than planned, to protect public health and environment. The quality and quantities of sludge produced at a municipal treatment facility are controlled by the composition of the incoming wastewater and the required treatment. The sludge characteristics, in turn, affect the alternatives available for treatment, beneficial use and disposal. Different sludge treatment processes will yield different types and volumes of sludge which can effect the beneficial use/disposal options available. The proposed beneficial use / ultimate disposal of the sludge solids dictate the extent to which the sludge must be treated prior to disposal. Various alternatives for sludge treatment and disposal are presented in Figure (1), Table (1). Figure (1): Sludge Disposal Alternatives
  • Table (1): Sludge treatment processes and their functions Unit Processes Function Thickening gravity, flotation, belt thickeners Water Removal Volume Reduction Blending Biological Stabilization Aerobic Digestion Anaerobic Digestion Composting Pathogenic Destruction Volume and Weight Reduction Odor Control Putrescibility Control Gas production (methane) (Anaerobic Digestion) Conditioning Chemicals, heat, fly ash Improve Dewatering rate Improve Solids capture Improve compactability Belt Filters Water Removal Solids capture Change to Damp Cake Volume and Weight reduction Dewatering Vacuum Filter Belt Filter press Filter press Centrifuge Water Removal Solids capture Change to Damp Cake Reduces Fuel Requirements for Incineration/Drying Drying Beds Heat Drying Water removal Incineration Destruction of solids Water removal Conversion Sterilization Final Disposal irrigation and croplands Energy Land reclamation and Landfill ocean disposal (Banned in USA) Incineration Wet oxidation
  • Location and capacity (current and planned) of all WWTPs: Alexandria has 18 wastewater treatment plants, ranging from 3,000 m3/day to 607,000 m3/day. Total capacity is about 1.4 MCM/day, of which 1.3 MCM/day is concentrated in 4 large treatment plants. About 1 MCM/day is currently upgraded to secondary. 0.3 MCM is already secondary. Planned capacity increase is 0.55 MCM/day. The East Treatment plant is currently a primary treatment plant under upgrading to secondary activated sludge treatment and discharges to Dayer El-Matar drain to Lake Maryout. Abis Villages 6 secondary treatment plants; The 10th Abis TP discharges to El Amlak drain, Nasriya TP to Dayer El Matar drain, Abis 1st and 2nd TPs to Mansheya Drain, Abis 3rd TP to Mansheya 3 drain and Abis 4th to Mansheya 4 drain. The West Treatment plant (primary under upgrading to secondary Activated sludge treatment) discharges directly to Lake Maryout. The Km 26 secondary activated sludge treatment plant does not discharge its effluent but it is reused by Alex West Tourist Compound adjacent to the treatment plant. Iskan Moubarak secondary TP discharges to Amriya drain, while Khorshid & Zawayda TP and El Maamoura TP are secondary treatment plants and discharge to Amiaa Drain. El Hannovile secondary treatment plant (Ard El Hesh) discharges near El Dekhila Harbour. El Seiouf secondary treatment plant disharges to El Qalaa Drain. El Agamy Km 21 Treatment plant will discharge to West Noubariya drain. And El Amriya secondary treatment plant will discharge to Noubariya canal. While el Noubaria secondary treatment plant discharges to El-Shagaa drain. New Borg El-Arab secondary Aerated lagoon treatment plant discharges to its surrounding forest area which is considered reused. It is proposed to discharge the rest unreused effluent to the West Noubaria Drain. Sludge generation (location, quantity, quality), processing and disposal.
  • The sludge from both ETP and WTP is mechanically dewatered at the WTP. The liquid primary sludge is pumped from the ETP to the WTP where it is co-settled with sewage and the sludge is dewatered by the belt press to about 30% dry solids (ds). Sludge production is currently about 450 m3/d, equivalent to about 50,000 tonnes dry solids (tds per year). This will increase when the WWTPs are extended (currently under development) and secondary treatment is installed (planned for 2010), reaching about 80,000 tds by 2015. Table (2) shows the current and future sludge production in Alexandria. The generated amount of sludge from the East Treatment plant that resulted from clarifiers is about 3000-4000 m3/d , solid concentration 2-3%, it is diluted to 1-2% then pumped through middle zone tunnel (12 km length, 5 m depth), to WTP, then dewatered by mechanical dewatering facility. Table (2) : Current and Future sludge production in Alexandria main treatment plants (m3/d) Year ETP/WTP Current 2009 2010 2015 2020 2025 450 669 724 724 759 759 Amriya TP 169/109 169/109 169/109 169/109 445/285 Hannoville TP 352 364 376 388 400 Total 450 1,190/1,130 1,257/ 1,197 1,269 / 1,209 1,316 / 1,256 1,604 / 1,444 The amount of sludge generated from the West treatment plant is also about 3000-4000 m3/d with solid concentration of 3-5% , then to the mechanical dewatering facility, The produced sludge is 8704 Ton/month; Used polymer 6927 kg polymer/month; Polymer cost 182873 L.E/month.; Dewatering efficiency 27.9%. The generated sludge from El-Hannoville TP and Iskan Moubarak TP is dewatered by centrifugation, with solid concentration of 25-30%, transported to 9N. The Mex/Dekhila/Agamy WWTP is initially expected to produce 200 m3/d of 20% ds, increasing to 400 m3/d by 2025. This will be a conventional primary sedimentation and activated sludge plant. The total quantity of sludge that will be produced by Alexandria will be about 1,200 m3/d by 2015, equivalent to about 150,000 tds/y.
  • The produced composted sludge has an average of 34 % Organic matter, 3% Total Nitrogen, 175 mg/kg available phosphorus. The heavy metals contents of the compost are within the required limits of Egyptian regulations. Sludge Treatment and Disposal system: Site 9N is located 35 km west of Alexandria. The site receives sludge cake from the MDF and grit, scum and screenings removed from the ETP and WTP. Grit, sand and screenings generated from the ETP and WTP are transported to site 9N by dump trucks. Currently, the total quantities transported of sludge are 83212 m3/year, of sand is 7973 m3/year and of screenings is 1749 m3/year, and from Industrial solid waste 3338.85 m3/year according to values of year 2008/2009. At Site 9N, a composting plant is established when the site was initially developed as a dedicated disposal area for the sludge. Consequently, land spreading of the sludge on the dedicated disposal area has ceased and all of the current production of raw sludge is now being composted using the turned windrow technique as shown in Figure (2). Figure (2) : Composting Processes of Dewatered Sludge. Mature compost is used as a bulking agent to improve the aeration of the composting process and is mixed on a 1:1 volume basis with the fresh dewatered raw
  • sludge, delivered daily to Site 9N. Specialized windrow turners are used for mixing the materials and for process (temperature, moisture) control in the windrows. Some mixing and turning is also done by mechanical shovel. A 30-day period is allowed for the active composting phase in windrows, following which the compost is removed to a curing and stockpile area where it is allowed to mature for several weeks, but the compost may be stored for many months before sale and use. Based on these assumptions, 1 m3 of dewatered sludge is converted into 0.4 m3 of matured compost. Therefore, at the current sludge production level, compost production is likely to be about 66,000 m3/y, rising to 184,000 m3/y by 2015, and 234,000 m3/y by 2025, based on the estimated increases in sludge production Assessment of the current Mechanical Dewatering Facility (MDF) conditions: 1- Hydrogen sulfide problems, which resulted from the septic condition of sludge at the equalization tanks and different location of sludge dewatering operations, thus affecting life time of the MDF components. 2- Produced quantities of dewatered sludge (30%) of the designed value. 3- Reduction in sludge dewatering production results in accumulation of the sludge in the end effluent channel of the WTP, affecting primary treatment operation efficiency. According to ASCDO committee (no. 931 dated 30/11/2008) recommended the following to improve MDF performance: 1- Starting rehabilitation of current belt press components. 2- Keep the safe level of H2S concentration. 3- Repairing and operating the blowers to ensure continuous mixing of liquid sludge in equalization tanks, homogenizing SS concentration and prevents septic conditions. 4- operating MDF hydrogen sulfide control unit. 5- Rehabilitation of computer systems. It is a must to increase the efficiency of mechanical dewatering operations to guarantee dewatering all sludge from primary treatment plants. Control of odor emissions from the current wastewater treatment plants by taking appropriate operating measures is not implemented to mitigate any noncompliance.
  • Assessment of Sludge/Solids Disposal Facility (9N) Composting significantly reduces the volume of sludge. During the composting process, there is a substantial loss of water during composting (reducing from 70% to 10% moisture content) but the density of the product will become less than that of the sludge because of its open texture (reducing from 1 to 0.7 m3/t). The amount of dry solids will also be reduced through the mineralization of organic matter (20% loss assumed). The volume of the compost will be increased by using matured added to facilitate the composting process, but this is in effect internal relying within Site 9N and so does not influence the net volume of compost produced for marketing. The assessment indicated that the thermophilic composting temperatures of 55–65ºC are evolved during composting. The temperature of the compost is stable within this range for up to two months and is relatively insensitive to the frequency of turning. The compost windrows do not require many turnings to maintain efficient processing, which is desirable for moisture retention since high moisture loss is likely to limit microbiological activity. Sludge Handling, Treatment and Disposal The goal of any wastewater residual solids disposal system is to dispose of solids in a cost-effective manner that protects the public health and the environment. Sludge disposal has historically been a major challenge in the wastewater treatment field. Approximately half of the operation and maintenance costs for a typical wastewater treatment operation are incurred in the sludge disposal processes. Current means of disposal in use in the U.S. include incineration, landfilling, ocean disposal and land spreading. All of these means have drawbacks; they are either too costly to operate or they may create a potential threat to the public health and environment. Therefore, an economical sludge disposal process that ensures protection of public health and the environment must be developed.
  • Table (3) : Expected Sludge Production from different wastewater treatment plants Area Treatment plant Amount of sludge produce ton/day (25% solids) 2012 2013 2014 2015 228 234 294 324 324 648 El Hannovile 60 60 60 60 60 60 Iskan Moubarak 18 25.2 25.2 25.2 25.2 25.2 Km 26 4.8 12 12 12 12 12 Km 21 180 192 204 216 216 216 Amrya 0 0 108 120 144 144 King Mariot 0 0 36 48 60 60 Abo talat 0 0 12 12 12 12 Borg Elarab (old) 52.8 52.8 52.8 52.8 52.8 52.8 Borg Elarab (new) 0 0 84 96 108 138 East TP 330 330 720 720 720 720 Elsiouf West 2011 West TP East 2010 8.4 8.4 8.4 8.4 8.4 8.4 Elmammoura 2.4 8.4 24 30 36 42 Khorshid 18 48 54 54 54 54 Abis (6TP) 21.6 21.6 21.6 21.6 21.6 21.6 Daily total 924 992.4 1716 1800 1854 2214 Monthly total 27723 29775 51483 54003 55623 66423 Annual total 337295 362261 626375 657035 676745 808145
  • Suggested scenario for Sludge management in Alexandria This scenario aims to manage the sludge production in the near future 2015. All Alexandria wastewater treatment plants will be in operation, so the sludge management will depend on collection of all sludge produced from the new small treatment plants and large treatment plants. Then, the dewatered sludge will be transported to treatment sites by large vehicles in order to be treated and disposed. Figure (3): Flow diagram of the sludge treatment by using windrow composting Figure (4) : Unloading of Sludge. Figure (5) : Covering of dewatered sludge with composted sludge.
  • Figure (6): Turning of windrows with composting machine. The steps of the plan could be as follows: 1- Sludge handling a- The sludge produced from East wastewater treatment plants The East Treatment plant is a central plant located east of Alexandria which will produce around 720 ton/day dewatered sludge. The dewatered sludge produced from all small treatment plants in the east of Alexandria will be collected there. The small secondary treatment plants are: • Maamoura T.P. will produce around 42 ton/day of sludge. • Khorshid and Zawieda T.P will produce around 54 ton/day. • EL seiouf T.P. will produce around 8.5 ton/day of sludge. • The Abis treatment plants (six treatment plants) will produce around 21.5 ton/day of sludge. b- Sludge produced from Amyria and Agami wastewater treatment plants The sludge produced from Iskan Moubarak T.P. (will be around 25 ton/day) and will be transported to Amyria T.P. which will produce around 144 ton/day. All sludge produced from both treatment plants will be transported to site 9N. c- The Km 21 treatment plant which will produce around 216 ton/day of sludge will be the collection point of sludge produced from both Hannoville T.P. and Km 26 T.P. • Hannoville T.P. will produce around 60 ton/day of sludge. • Km 26 T.P. will produce around 12 ton/day of sludge. d- The sludge produced from West wastewater treatment plants The sludge produced from the West treatment plant will be around 648 ton/day which will be transported directly to site 9N.
  • 2- Sludge treatment system Composting area of site 9N is 140 feddans which has been used for sludge composting as shown on Figure (7). Figure (7) : Location of Site 9N and the proposed extension area. Site 9N is the most suitable location for composting operation, where it is downwind of the near houses and can easily be managed as a composting area. The composting area contains 180 windrows of 250 length, 1.5m height and 4m width. The distance between each two windrows is 5 m. For building a windrow, 35 – 40 trucks containing 20 m3 of sludge cake are required (700 m3 – 800 m3), construction of one windrow takes from 2-3 days. The spoil material storage area is utilized for emergency use. For adopting windrow composting method to treat non stabilized primary sludge the windrows are covered after each turning with a 5 cm layer of matured compost to minimize the flies' attraction, especially during first week of composting period. Also, ten centimeters matured compost is used during construction at the bottom to prevent septic condition at the lower layer of the windrows. The expected total quantity of dewatered sludge produced in Alexandria will be around 2000 ton/day. This quantity will be sent to site 9N for treatment and disposal. Currently Site 9N has two areas for sludge composting, south and north composting areas 30 hectares each. In addition to a storage area of about 15 hectares. The total
  • capacity of sludge treatment at site 9N is about 150,000 tons, which is equal to sludge produced from Alexandria treatment plants during 75 days. The sludge treatment process takes three months (two months fermentation period and one month curing period) which indicates that the composting area at site 9N is not enough to receive the sludge in the nearest future (2015), therefore it is important to find another new composting site with an area of about 200 feddans. The site suggested is the extension of site 9N to the west direction which has a large unused desert area surrounded by agriculture fields Figure (7). The suggested new site should be designed as the follows: 1- Composting field 120 feddan serviced with ground and surface water protection system. 2- Storage area about 40 feddan which must be beside the composting area. 3- Site utilities about 40 feddan which include the following: - Administrative buildings - Maintenance work shop. - Temporary storing area for equipments. - Equipment washing area. - Roads and trees surrounding the site area. (as shown in Figures (8,9)) North Composting area South Composting area Figure (8): Suggested new site design.
  • Figure (9): Suggested new site after extension. 3- The sludge produced from Borg El -Arab wastewater treatment plants The sludge produced from Borg El-Arab treatment plants -about 200 tons/day- will need to be treated in situ, and so we need to establish two sites for sludge treatment in Borg El-Arab city. The area of each sludge treatment site should be about 70 feddans, 60% of the proposed site should be used for sludge treatment, 20% for sludge storage and 20% for traffic building and equipments. The suspected new site design is as the follow as shown in Figure (10). 1- Composting field 42 feddan serviced with ground and surface water protection system. 2- Storage area about 14 feddan which must be beside the composting area. 3- Site utilities about 14 feddan which include the following: - Administrative buildings - Maintenance work shop. - Temporary storing area for equipments. - Equipment washing area. - Roads and trees surrounding all site.
  • Figure (10): Suggested new sludge treatment site for Borg ElArab. The sludge management system of Borg El Arab city will depend on the characteristic of each dewatered sludge batches. As a result of laboratory chemical analyses, batches characterized with high contents of hazardous industrial waste must be collected and transferred to site 9N for sanitary landfill. The batches satisfy with the Egyptian criteria for sludge reuse especially in terms of heavy metals will loaded into windrow composting area. References: 1- Integrated Urban Water Management (IUWM), CEDARE/SWITCH project (2010), "New Strategies for Wastewater Management and Reuse in Alexandria in 2037" 2- Malina Joseph F.,. Sludge Handling, Treatment and Disposal Processes. Workshop on Domestic wastewater treatment and sludge Disposal processes. The American University in Cairo. 17-20 April 1995..
  • 3- Sludge Handling and Conditioning, Operations Manual. U. S. EPA, Washington, (1978). 4- Wastewater Research Group (WRC), Alexandria Effluent and sludge Reuse Study . Alexandria, ARE., January 2000. 5- Wastewater Research Group (WRC), Alexandria Effluent and sludge Reuse Study . Alexandria, Final Report March 2001. 6- Egyptian Code ECP 501-2005, (2005). “Egyptian standards for use of treated wastewater in agriculture". World Academy of Science, Engineering and Technology 57 2009. 7. Master plan of Alexandria wastewater system 2007) 8. M. Ghazy, T. Dockhorn, and N. Dichtl, Sewage Sludge Management in Egypt: Current "Status and Perspectives towards a Sustainable Agricultural Use, World Academy of Science, Engineering and Technology 57 2009.