International Journal of Renewable Energy and Environmental Engineering ISSN 2348-0157, Vol. 02, No. 04, October 2014

Performance evaluation of central effluent treatment plant in Depz, Savar, Bangladesh AHMUD FAHIM, KH. MAHBUB HASSAN Department of Civil Engineering, Khulna University of Engineering & Technology, Bangladesh Email: [email protected], [email protected] Abstract: Wastewater management is a concept involving several operations, which depend on the scale and nature of industry or institution and end use of wastewater. Central effluent treatment plant (CETP) is an approach of treating effluents by means of a collective effort mainly for a cluster of small scale industrial units. A biometric CETP was launched in Dhaka Export Processing Zone (DEPZ) and started operation for wastewater treatment in February 2012. It was the first of its kind in Bangladesh to utilize a Bio-Electric treatment profile on a co-mingled industrial wastewater stream with an average wastewater inflow of 1750 m3/hour. The treatment system offers tremendous advantages. Operating costs were low compared to chemically enhanced treatment and provided substantial difference (as much as 85% less) in sludge generation. It also had positive removal impacts on other contaminants that might appear as a part of total (co-mingled) wastewaters entering CETP from DEPZ factories. In this case, the use of chemicals was totally avoided and hence not required any neutralization as well as minimization of secondary pollutions by added chemicals. The present study was undertaken to evaluate the performance of the biometric CETP especially with regards to effluent water quality. Wastewater samples were collected from Primary and Secondary stages of treatment units and the major water quality parameters such as pH, Biochemical Oxygen Demand (BOD), Chemical Oxygen Demand (COD), Total Suspended Solids (TSS) and Total Dissolved Solids (TDS) were analyzed following the standard methods for the examination of water and wastewater. The Primary-stage treatment operation was done with Activated Sludge Process while the Secondary-stage involved Electro Contaminant Removal. Finally, the effluents from the biometric CETP were compared with the Bangladesh Standards for wastewater quality discharging into various receiving bodies. The Environment Conservation Rules (ECR, 1997) of the country has set a range of water quality standards for different receiving bodies such as Inland Surface Water, Public Sewer, and Irrigated Land. In biometric CETP, the removal efficiency of BOD was found to be 97.40% while the Dissolved silica, Clays, Carbon black and Suspended materials in water were removed generally around 98%. The Treatment Plant reduced Bacteria, E-coli and Viruses almost completely. Emulsified oily substances as well as heavy metals in water such as arsenic, cadmium, chromium, lead, nickel, and zinc were removed in the range of 95 to 99%. Both the primary and secondary stages of treatment operations were found to have significant contribution in the overall treatment performance of the biometric CETP upholding the final effluent quality within the permissible limits of ECR, 1997. Keywords: Bio-Electric treatment, Central Effluent Treatment Plant, Co-mingled Industrial Wastewater, Performance Evaluation 1. Introduction: Water is the basic need of all life, human, well-being and also for economic development. Because of increasing industrialization, urbanization and other anthropogenic activities, and the water quality is getting degraded day by day. Waste water management is a concept involving several operations, which depend on the scale and nature of industry or institution and end use of wastewater. The objective of wastewater management at the present scenario is to solve the environmental pollution problems and water scarcity by adopting reducing, reusing or recharging methodologies. At present the conventional methods of wastewater treatment are working with a limited treatment efficiency to comply with the requirements of the regulatory bodies. Besides it is difficult for each industrial unit to provide and operate individual wastewater

treatment plant because of the scale of operations or lack of space or technical manpower. However, the quantum of pollutants emitted by small scale industries may be more than an equivalent large-scale industry. Common Effluent Treatment Plant is the concept of treating effluents by means of a collective effort mainly for a cluster of small scale industrial units. The main objective of CETP is to reduce the treatment cost for individual units while protecting the environment and to achieve economical waste treatment, thereby reducing the cost of pollution abatement for individual factory [06038_CETP_Report, November 2000]. However the effectiveness of the wastewater management will depend on the treatment methodology, operation and maintenance of the equipment and the commitment of operation/management personnel. Prevention of pollution of natural resources such as land and water by the waste water and adequate preparation or

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AHMUD FAHIM, KH.treatment MAHBUB HASSAN Performance evaluation of central effluent plant in Depz, Savar, Bangladesh

renovation of the wastewater before reuse, are further important considerations in formulating and designing appropriate waste water disposal arrangements. The degree of treatment provided to the wastewater will largely be based on the effluent standards prescribed by the regulatory agencies when the treated effluent is to be discharged into a watercourse or land. If the effluent is to be reused, the quality of the effluent required to support such reuse will indicate the degree of treatment necessary. The complete treatment of wastewater is brought by a sequential combination of various physical unit operations, and chemical and biological unit processes. The general yardstick of evaluating the performance of sewage treatment plant is the degree of reduction of BOD, and suspended solids, which constitute organic pollution. Performance evaluation of existing treatment plant is required to assess the existing effluent quality and/or to meet higher treatment requirements and, to know about the treatment plant whether it is possible to handle higher hydraulic and organic loadings. Performance appraisal practice of existing treatment plant units is effective in generation of additional data which also can be used in the improvement in the design procedures to be followed for design of these units. Existing facilities can be made to handle higher hydraulic and organic loads by process modifications, whereas meeting higher treatment requirements usually requires significant expansion and/or modification of existing facilities [EPA, US, (1974)]. One of the primary considerations in evaluating an existing wastewater plant is in the area of plant operation and control, proper process control in frequent and accurate sampling and laboratory analysis. Poor conditions of sewerage system, improper design of the plant and organizational problems are important factors that cause treatment plant not to meet the effluent standards [Storhaug, R. (1990)]. Overloading due to increase in population and water use, discharge of trade effluents are other reasons of recent times for the poor performance of waste water treatment plants .The treatment efficiency may be badly affected if the system is hydraulically under loaded [Kapur, A., Kansal, A., Prasad, R. K. and Gupta, S (1999)]. An export processing zone (EPZ) is defined as a territorial or economic enclave in which goods may be imported and manufactured and reshipped with a reduction in duties / and/or minimal intervention by custom officials (World Bank 1999). DEPZ (Dhaka Export Processing Zone) is situated in Savar. 35 kms 1997(The Environment Conservation Rules) for Inland Surface Water, Public Sewer, and Irrigated Land [Guide for Assessment of Effluent Treatment Plants].Reduction Capabilities and Removal Rates of several other parameters in Primary Stage (Activated

from Dhaka city centre, 25 kms from Hazrat Shah Jalal (R) Airport, 304 Kms from Chittagong Sea Port. Because of this suitable location, As on December, 2010, a total of 94 industries have invested 785.93 million US dollars in here, and by 2012-13 (February, 2013) it has risen to 911.64 million US dollars [BEPZA].To ensure safe water and environment for the inhabitants of Savar and outskirts, by way of protecting biodiversity, natural resources and water bodies, a biometric central effluent treatment plant (CETP) is constructed on a stretch of 16,000-square-foot area of DEPZ old zone and it started its treatment in February’ 2012. It is the first of its kind in Bangladesh and a first in the world to utilize a Bio-Electric treatment profile on a comingled industrial wastewater stream. The Plant possesses the best and latest combinations of technology and equipment provided and manufactured by Singapore company Flagship Ecosystems Investment Private Limited (FESI) [June 28, 2012 - (ACN Newswire)]. It has the capacity to treat 43, 000 cubic meters of water and 15,000 cubic meters of ECC from DoE per day. The recycled water will be poured into nearby Dholai Beel. The main objectives of this study is to analyze the overall performance of the Central Effluent Treatment Plant and the removal rates of various parameters like pH, BOD, COD, TSS and TDS as well as performance and removal efficiencies of the individual units in the primary and secondary treatment.

Fig 1.1: Google image of DEPZ Central Effluent Treatment Plant [C.E.T.P] 2. Methodology: Waste water samples were collected at different stages of treatment units and analyzed as outlined in the standard methods for the examination of water and wastewater [American Public Health Association,]. The samples were analyzed for various parameters like pH, BOD, COD, TSS and TDS and compared with Bangladesh National Standards for Waste Discharge Quality according to ECR Sludge Plant) and by Secondary (ECR) Treatment were also analyzed.

International Journal of Renewable Energy and Environmental Engineering ISSN 2348-0157, Vol. 02, No. 04, October 2014, pp 315-321

Performance evaluation of central effluent treatment plant in Depz, Savar, Bangladesh

2.1 Commissioning procedures of treatment: Waste water gets diverted to CETP. All sluice gates are closed. Tank 2 (Fig. 2) is allowed to fill and overflow to by-pass channel. The integrity of Tank 2 is checked and Drum Screens are powered up. Sluice gate is opened and integrity of Tank 4 is checked. Drum Screen rotation is started. Main Lift Pumps start up sequentially 1,2,3,4. Pump 1 fills Tank 8B. Pump 2 fills Tank 6. Pump 4 fills Tank 8A.When the height of 6 reaches 1/3 of tank height pumps will be shut down (i.e. 2&3 ). When 8A/8B reaches 1/3 height all pumps will be shut down. The integrity of Tank 6, 8A/8B are checked. It is held for 6 hours and Drum screens are shut down. After 6 hours all pumps are started up to fill 6, 8A/8B to full overflow level. When 7A/7B is full shut all pumps and integrity is

checked. All 4 main pumps are re-routed to Tank 6. Pumps are started. Overflow to Clarifier Tank 10 is done just before to Tank 11. Pumps are shut and integrity is checked. Then pumps are started to overflow Tank 11. Pumps are stopped when Tank 11 is full and integrity is checked. Then ECR feed pumps are started. Overflowed to Tank through 13 and held. Integrity is checked. Tank 13 is allowed to overflow. Clarifier Tank 12 until overflow to Tank 14. Pumping is started from Tank 12 bottom to fill Tanks 16/17/18. Integrity is checked. Then it is held for 24 hours and full inspection is conducted on all Tanks integrity for leaks, cracks and other faults

.

Fig 2.1: DEPZ Central Effluent Treatment Plant Detail Layout.

2.2 Treatment Procedures: The treatment process can be divided in two steps: Activated Sludge Plant (ASP)-Primary Treatment and Electro Contaminant Removal (ECR)- Secondary Treatment. The process is shown in a flow chart below:

International Journal of Renewable Energy and Environmental Engineering ISSN 2348-0157, Vol. 02, No. 04, October 2014, pp 315-321

AHMUD FAHIM, MAHBUB Performance evaluation of central effluentKH. treatment plant HASSAN in Depz, Savar, Bangladesh

Fig 2.2: Process Flow Diagram of Central Effluent Treatment Plant at Dhaka EPZ. 3. Results and discussion: The evaluation of performance efficiency of the plant was undertaken in terms of effluent quality. The evaluation was based on the plant operation data such as pH, Bio- chemical Oxygen Demand( BOD), Chemical Oxygen Demand (COD), Total Suspended Solids, Total Dissolved Solids, measurements for the period of 5 weeks from February '13 to March"13 . The variations of these parameters during the study are shown graphically in Fig 3.1, Fig 3.2, Fig 3.3, Fig 3.4 and Fig 3.5. It has been observed that the overall treatment efficiency for the BOD removal is 97.40% and that for Total Suspended Solids removal is 98%. Fig 3.1 shows the variation of the values of pH of the collected samples as well as their average value and the national standard foe pH according to ECR 1997. The samples have an average pH of 7.39. The ECR

1997 standard of pH for Inland Surface Water, Public Sewer, Irrigated Land is 6-9. Fig 3.2shows the variation of the BOD values having an average of 44.5 mg/l. The national (ECR 1997) standard for BOD for Inland Surface Water is 50 mg/l, Public Sewers 250 mg/l, Irrigated Land is 100 mg/l which is also shown in the figure.

Fig 3.1: Variations of pH

International Journal of Renewable Energy and Environmental Engineering ISSN 2348-0157, Vol. 02, No. 04, October 2014, pp 315-321

AHMUD FAHIM, MAHBUB Performance evaluation of central effluentKH. treatment plant HASSAN in Depz, Savar, Bangladesh

Fig 3.2: Variations of BOD

Fig 3.3: Variations of COD

Fig 3.3shows the variation of the COD values (average of 134 mg/l).It also shows the national (ECR 1997) standard for COD values for Inland Fig 3.4 & Fig 3.5 shows the variation of the TSS and TDS values in the collected samples respectively.

Surface Water which is 200 mg/l & for Public Sewers and Irrigated Land a value of 400 mg/l. They also show the national standard for these parameters according to ECR 1997.

International Journal of Renewable Energy and Environmental Engineering ISSN 2348-0157, Vol. 02, No. 04, October 2014, pp 315-321

Performance evaluation of central effluent treatment plant in Depz, Savar, Bangladesh

Fig 3.4: Variations of TSS

Fig 3.5: Variations of TDS DEPZ Central Effluent Treatment Plant has a sequential contaminant removal process. After the pre-conditioning and equalization the primary treatment starts in the Activated Sludge Plant (ASP) which consists of Neutralization – Feeding Section, Oxidation tank, Clarifier, and Sludge retaining conditioning sections. Table 3.1 shows in detail the reduction capabilities and removal rates (average values)of the various parameters present in the effluent in Primary Stage

Table 3.1: Reduction Capabilities and Removal Rates in Primary Stage/ Activated Sludge Plant (ASP) Parameters Wastewater flow rate

Specifications 1750 m3/hour

ECR 1997

Inherent Fibrous material and 2mm removal@ Lint 75% RAW Influent MIX parameters and combined bio & electric reduction values

Raw

Raw Pri Pri

See See

Raw

Color Chemical Oxygen Demand (COD) [industrial-sewerage-rinse waters] Biochemical Oxygen Demand (BOD) Post bio before ECR COD Post ECR after clarification COD

300 Pt Co unit 500-700 mg/l

Post bio before ECR BOD Post ECR after clarification BOD

83-115 mg/l 33-46 mg/l

50

Total Suspended Solids (TSS)

350 mg/l

150

166-230 mg/l 250-350mg/l 100-140mg/l

200

Remarks 24 hours CETP operations Automated fine screen Bio – Electric removal % 90% removal by ECR Assumed total comingled streams

Assumed to be 1/3 of COD value 60% COD reduction with aeration by ASP Minimum COD reduction up to 60% by ECR 60% BOD reduction with aeration by Minimum BOD reduction up to 60% by ECR TSS- 90% reduction with secondary separation techniques/Clarifier

International Journal of Renewable Energy and Environmental Engineering ISSN 2348-0157, Vol. 02, No. 04, October 2014, pp 315-321

Performance evaluation of central effluentKH. treatment plant HASSAN in Depz, Savar, Bangladesh AHMUD FAHIM, MAHBUB

Raw

Total Dissolved Solids (TDS) pH

Average 1500 mg/l Average 7.5 – 8

Raw

Dissolved Oxygen (DO)

1.5-3.0 mg/l

DO

4.5-5.0 mg/l

Ammonia Nitrate Arsenic