Waste to Energy Sewage Treatment Plant Delawas Jaipur, Rajasthan, India, a Case Study Dharmraj Jangid 1*, Akhilendra B. Gupta 2#

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1 Waste to Energy Sewage Treatment Plant Delawas Jaipur, Rajasthan, India, a Case Study Dharmraj Jangid *, Akhilendra B. Gupta # Research Scholar, Professor, Civil Engineering Department, Malaviya National Institute of Technology, Jaipur, Rajasthan, INDIA Abstract: Power consumption accounts for almost % of the expenditure on O and M of any sewage treatment plant working on aerobic biological process. STP Delawas, Jaipur based on conventional activated sludge process was commissioned by RUIDP in 00 with a capacity of. MLD. The average daily power consumption for operation of STP is Kwh, which amounted to an electricity bill of more than. million per month prior to the installation of power generation unit based on biogas fuel. Apart from power generation, energy saving measures taken for the plant operations has resulted in substantial saving in the energy costs. Air blowers are being operated with Variable Frequency Drive (VFD). Man Machine Interface (MMI) is provided through Programmable Logic Control System (PLC) for handling anaerobic sludge digesters that produce about Nm of gas per day, which is being utilized for power generation. An analysis of three year data shows that the maximum power generated was about 0 Kwh/month in March, 00 (Av. Kwh/day) and lowest kwh/month in February, 0(0 Kwh per day) through gas engine. The value of generated power through biogases is about.-. million/ month (about -0% of power requirement) which is a good example of Waste to energy (WTE). This has made the STP almost self sufficient (except for meeting peak hour demand) in terms of power requirements. This study give us a though at the design stage, concept of waste to energy and improvement in efficiency of primary clarifier to get more primary sludge for anaerobic digestion to produce more biogases to get more power which will further reduce the power requirement from grid. The increase in sludge at PST will reduce the BOD load on secondary treatment unit and will help in reduction in power consumption of aeration tank. Keywords: STP- Sewage Treatment Plant,BOD- Biochemical Oxygen, TSS- Total Suspended solids,asp- Activated Sludge Process COD-Chemical Oxygen Demand, WTE- Waste to Energy. Introduction Sewage treatment is a significant user of energy. Operation of pumps, blowers and other equipment at a typical sewage treatment plant (ASP /extended aeration) per person an annual electrical energy consumption requirement is in the range of - KWh (Arceivala and Asolekar, 00). Thus, substantial input of energy is required to treat sewage from densely populated areas, Corresponding Addresses: * jangid_dr@rediffmail.com, # akhilendragupta@yahoo.com Research Article and sewage treatment often comprises the largest use of electricity by local governments. Conventional STPs remove organic content from the water stream by reacting the proteins, fats and carbohydrates with oxygen from the air. This oxidation process is undertaken at ambient temperature by the enzymes secreted by aerobic bacteria and converts most of the organic material to carbon dioxide and water through dissimilatory process. The process also produces sewage sludge, or bio-solids, consisting of un-oxidized organic matter and predominantly bacterial cells. Some treatment plants further reduce the quantity of bio-solids through an anaerobic treatment process. Here, in the absence of air, anaerobic bacteria digest the bio-solids, producing "biogas", a mixture of methane and carbon dioxide. Methane is the main component of natural gas, and the biogas produced, can be burnt in an engine or turbine to produce power and generate electricity. In this way, anaerobic treatment can generate electrical energy used in the sewage treatment plant. Case Study of STP Delawas Rajasthan Urban Infrastructure Development Project (RUIDP) constructed and commissioned a.0 MLD STP at Delawas, Jaipur. The STP is in operation since beginning on its full design capacity. The STP is in operation since beginning on its full capacity. The figure - shows the sewerage coverage area of south zone of Jaipur city from Vidhyadhar Nagar to Pratap Nagar Sanganer. The farthest point is about Km from STP and nearest is Km. from STP. There is no pumping in sewerage network laid up to STP. Main trunk sewer reaching at STP site is 00 mm in diameter Figure- shows the general Layout of STP. Rs. word is to be added in Table, Table ( Rs. in million) International Journal of Recent Trends in Science And Technology, ISSN - E-ISSN -0, Volume 0, Issue, 0 Page 0

2 Dharmraj Jangid, Akhilendra B. Gupta Jhotwara Khatipura Vaisali Nagar Mansarovar Sanganer Water supply- about- 00 MLD Population-.00 lacs Sewerage coverage- about - 0% area No intermediate pumping in laid sewer system Major area divided in two parts (for sewer network) South area- MLD North east area- + 0 MLD New coverage- East south- 0 MLD North west- 0 MLD West- Not covered through under ground sewer North area-murlipura 0MLD Westnot covered 00 mm trunk main sewer SEWAGE FLOW - JAIPUR Vidhydhar nagar North Shstrinagar east area- MLD + 0 MLD C scheme Tonk Road Bapu Nagar Jawahar Nagar Malviya Nagar Sewage collection Area of Jaipur city Pratap Nagar East-South area - 0MLD JAWAHAR NALLAH. MLD STP AT DELAWAS Amanisaha Nallah South area- MLD Flow Treated Water Discharge Ramchandrapura Dam Figure : sewerage coverage area south Jaipur Figure : General layout of STP Salient Features of STP The Plant is based on conventional activated sludge process with diffused aeration system. Sludge is being handled in anaerobic digesters. Digested sludge is pumped to centrifuge unit where it is converted to semi solid form having consistency of % solids and used as manure. The salient features of STP are given below in table. Table : Salient Features of.0 MLD STP S. No. Particulars Details. Capacity: Present I Phase.0 MLD. Work cost Total Rs..00 lacs in year OandM cost for years is Rs.0 lacs for year OandM. Total land area Total Hectare, STP constructed in.0 Hectare.. Process Remaining area for future expansion. Activated Sludge Process with anaerobic Digester and centrifuge unit ( no sludge drying beds). Size of main sewer at STP 00 mm. Design flow on main sewer Total MLD The total guaranteed power consumption is Kwh/ day (more than this consumption, the cost is to be borne by the OandM contractor) for treatment of.- MLD sewage and daily actual consumption is about 0-00 Kwh/day indicating an average consumption of - Kwh/MLD of sewage treated or.-. Kwh/Kg of BOD removed (Vatech Wabag Ltd., Jaipur, STP site office). This is much lower than the values of 0- Kwh/MLD reported for conventional ASP based STPs under Yamuna Action Plan at Allahabad of capacities between 0-0 MLD (MoEF, 00). To save power, a Variable Frequency Drive (VFD) is provided which is governed through programmed feedback circuit based on Dissolved Oxygen (DO) levels maintained in the bulk aeration reactor. DO analyzer is connected to VFD, the VFD is controlled by signals generated and transferred by the DO Analyzers, in proportion to the dissolved oxygen content in the mixed liquor exits in the aeration tank compartments. The blowers, fitted with VFD to maintain the required dissolved oxygen concentration in the aeration, effectively control the required airflow rate. Aeration is carried out through retrievable type membrane diffusers, placed at the floor level, spanning the entire floor area for uniform distribution of air. A Separate mechanical type excess sludge thickener is provided to concentrate the excess activated sludge to a level of % solids through centrifugal action and another gravity sludge thickener is used to thicken the primary sludge to a similar consistency. Man Machine Interface is provided through PLC System, which controls all operations except those on the Gates, some valves and the F/M ratio. The STP including sludge handling units is functioning on full designed capacity. Operation and Maintenance Cost Operation and Maintenance for years of STP was with M/s Vatech wabag Ltd. Chennai who has constructed the STP. Power Guarantee was obtained for Kwh/day by the contractor during throughout the OandM period of years. OandM cost includes the cost of Man power, wear and tear of machinery, chemicals and maintenance of plantation. OandM expenditure of STP for the period 00-0 is given in table -. The per MLD operating cost is about Rs to treat municipal up to secondary level. Copyright 0, Statperson Publications, International Journal of Recent Trends in Science And Technology, ISSN - E-ISSN -0, Volume 0, Issue 0

3 Table : Operation and Maintenance Cost of STP O and M Charges of Plant Cost per month (in millions) For Power charges /Month OandM cost / Month* Total OandM Cost I year( 00-0) II year( 00-0) III year( 00-0) IV year( 00-0) V year( 00-) *Price escalation on O and M cost to be paid to contractor is also paid up to contract period (September 0) as per condition, according to RBI Index. Source: Vatech Wabag Ltd., Jaipur Characteristics of Sewage The average characteristics of wastewater received at STP and those of the treated wastewater are summarized in table, which have been obtained from the records of STP Delawas for a period of Jan-0 to April- for composite samples (sample drawn at an interval every hrs. to make composite sample on daily basis). The average per day sewage quantity is being treated is in the range of 0. MLD ( in April-0) -. MLD( in Aug- 0) in the period from Jan-0 to April- and average per day sewage is. MLD against designed flow of. MLD. The average parameters results in above period of influent and effluent are tabulated in table- Table : Characteristics of wastewater Parameters BOD (mg/lit) COD (mg/ lit) TSS(mg/ lit) ph Designed influent parameters Actual average (Influent) parameters.0 Designed effluent parameters Actual Average (effluent). Source: Vatech Wabag Ltd., Jaipur, Note:- values rounded off to nearest integer. The above results show that STP is functioning satisfactorily in terms of achievement of designed effluent parameters. Energy Conservation and Recovery From Sewage Treatment Plant Power consumption accounts for almost % of the expenditure on OandM of the plant. The average per day power consumption for operation of STP is Kwh, which presently amounts to a total electricity bill of about.-. million per month. Energy saving measures has The Characteristic and Calorific value of produced gases Table : Test results of biogas produced during sludge digestion Per day sludge generation gas generated during anaerobic digestion CH %v/v CO H S been taken for the plant operation that has resulted in substantial saving in the energy costs as stated above. For sludge handling anaerobic sludge digesters have been constructed and are in operation. The characteristics of gases produced during anaerobic digestion of sludge are given in table Calorific value Kcal/Nm -0 m/day Nm/ day Morning Sample no Samples were collected Mid day Sample tested and got tested by no. RUIDP at Shriram Test After noon Sample House, New Delhi no. Protocol/Method for GC-FID Orsat Apparatus IS- IS- 0 analysis Source: Vatech Wabag Ltd., Jaipur Produced Gases are collected through HDPE piping arrangement and allowed to pass through Moisture trap, scrubber unit and then collected in membrane made (balloon type) gas holders. Collected gas is then pumped to gas engine where power is generated. The estimation of power generation from the gases is given in table-. Item Average amount of Gas Generated From One. MLD Plant ( data taken from JMC) Gas consumption for 000 Kwh Table : Estimation of power generation from the digester Value 000M /DAY, 0M / hr in the range of Nm ( depending on the methane in produced gases) Calorific Value of Gas( based on test results given in table-) 000 TO 00 KCAL/M (Av value 00 KCAL/ M 000 KCAL=. Kwh International Journal of Recent Trends in Science And Technology, ISSN - E-ISSN -0, Volume 0, Issue, 0 Page 0

4 Dharmraj Jangid, Akhilendra B. Gupta Total Heat Energy of 0 Nm Gas Total energy in kw hour Efficiency of biogas engine and generator Electrical Energy can be produced Source: Vatech Wabag Ltd., Jaipur Cost Viability of Power Generation Plant Estimated cost of system to generate terminal power output of 00 KWh/day was.0 million in year 00. Annual maintenance cost -.% of total invested capital cost of.0 million. Thus expenses for running the plant per Kwh are.0. Present Purchase cost of Year Project execution Cost O and M cost /year Table : Cost viability calculations Cost in million. interest cost /year (@ % per year) 000 KCAL/hr 0 Kwh % and % respectively say 00 Kwh (00 unit/day) Power is.00 per Kwh. The per Kwh cost of electricity is taken as.0 for st year and.0,.,.,.0, 0.0,.0,.0,.0,.0 for subsequent years up to 0 years period. Accordingly, cost viability calculations are given in table-. Total Exp./ year Cost of power to be generated /year Saving/ year =(+) =(-) As per above analysis the expenditure can be paid back along with compound interest (@ %) in years (from Dec-0 to Nov-) after starting of the power generation unit. Thus, in remaining years (out of ten years OandM period) plant will generate cumulative power amounting to approx..0 million (in terms of money); which can be utilized for other works. About.0 million power units (Kwh) can be generated in 0 years period; this power can be gainfully utilized. As per above the pay Back Period is about - year. If standby unit is not provided the payback period will be about years. Status of Power Generation and Power Consumption At STP Delwas Unit-I The power required for operation of STP, Delawas is coming from two sources; first is from grid and second is from the installed bio gas based power plant (generated bio gas at Unit I which is used for power generation). The total installed power generation capacity is 0. (00Kwh) to.0 mega watt (000 Kwh) (including stand by Engine in operation). As per design, daily power consumption in operation process of Unit I is. Kwh/day and approximately 00 kwh/day is consumed in yard lighting. Figure shows the monthly guaranteed power consumption, actual power consumed, power generated, power taken from grid and monthly power saving at STP, Delawas Unit I:- Figure : Source: Vatech Wabag Ltd., Jaipur Copyright 0, Statperson Publications, International Journal of Recent Trends in Science And Technology, ISSN - E-ISSN -0, Volume 0, Issue 0

5 As per Data collected from JMC, prior to the commissioning of power generation unit, the average monthly power consumption was 0 Kwh /month, which was obtained from grid and for which about.-. million, monthly payment was made to JVVNL. But after power generation at plant site from December, 00 to April, 0, the average power consumed from grid is only Kwh/month. The maximum power consumed in the month of January, 0 is Kwh/month whereas minimum power consumed in the month of June, 0 is Kwh/month. Before power generation at plant, total power demand was fulfilled from the grid. Plant was facing major problem of unwanted power cutoff that was directly affected plant operation. But now an average % of total power demand is drawn from grid and the rest is met by the power generation at site. Conclusion The produced biogases contain -% of methane component which is being used to generate electricity of Av. 00 KWh/ day. The power generation Plant capital cost is about 0 lacs. The O and M cost for Power generation unit is about million/ month. The value of generated power through biogases is about.0-.0 million/ month which is a good example of Waste to energy (WTE). About -0% of required power is being produced thus STP can be made self sufficient in terms of power requirements and operation and maintenance also reuse of treated wastewater for agriculture, forestation, and groundwater recharge or pasture development without further treatment. This would further result in savings of power as pumping of groundwater from deep strata will be reduced in the surrounding area of effluent flow. At the design stage, consideration of waste to energy concept should be considered by the designer to reduce O and M cost of STP and improvement in efficiency of primary clarifier to get more primary sludge and reduce load on secondary treatment unit. Acknowledgement T t he authors acknowledge with sincere gratitude the help provided by Mr. P.C. Pandey Laboratory In-charge of STP Delawas, Jaipur as an employee of M/s Vatech Wabg Ltd, for this study. References. Arceivala Soli J. and Asolekar S. R. (00), Wastewater Treatment for pollution Control and reuse third edition, TMH, New Delhi.. Vatech Wabag Ltd., Jaipur, Records of plant operation at STP site office, Delawas, Jaipur.. MoEF (00). Compendium prepared by IIT Kanpur for NRCD- MOEF on Conventional ASP based STPs under YAP- Allahabd pp Paper presented in th annual convention of IWWA at Banglore India, in Jan-0 by the authors. International Journal of Recent Trends in Science And Technology, ISSN - E-ISSN -0, Volume 0, Issue, 0 Page