STRUCTURAL AND OPERATIONAL STUDY OF 339 MLD SEWAGE TREATMENT PLANT AT AMBERPET

Transcription

1 N RAMA KRISHNA, et al, [IJRSAE] TM STRUCTURAL AND OPERATIONAL STUDY OF 339 MLD SEWAGE TREATMENT PLANT AT AMBERPET N.RAMAKRISHNA, P.V.R.K.PRASAD ABSTRACT The project is titled STRUCTURAL AND OPERATIONAL STUDY OF 339 MLD SEWAGE TREATMENT PLANT AT AMBERPET.Asia s biggest STP with UASB (Up flow Anaerobic Sludge Blanket) Technology in terms of Capacity (339 MLD). 226 MLD Sewage is tapped from outfall sewer chamber. Pretreatment unit consists of 4 mechanical screens, 2 manual screens to prevent floating materials and conveyor belt for disposing screened materials and 4 degritting units of 56.5 MLD capacity for removal of grit. Grit is disposed through rake classifier mechanism. 226 MLD Sewage from these new units and 113 MLD sewage from the existing plant will collect in wet well of pump house and pumped to reactors by 12 pumps (12 Working + 6 Standby) of 210 HP capacity to a head of Mts over a length of 1.5 Km through 2 lines of M.S mm Dia Pipe Lines. UASB Reactor (24 nos 32 Mtr x 28 Mtr x 6.3 Mtr) is the place, where the separation of Gas, Liquid and solids takes place. BOD Load is reduced by 75% in reactors. Hydraulic Retention Time (HRT) is 8.88 Hours. Suspended solids settle down to form a blanket at the bottom, excess sludge will be taken to sludge pump house and pumped to Belt Press where moisture is removed and it is formed into sludge cakes, which could be used as manure (165 Cum/Day). Gases (6423 Cum/Day) formed like Methane and Hydrogen sulphide are collected in gas holders (3 Nos), methane is fed to pure gas engines to generate electricity (0.6 to 0.9 MW/Day), while Hydrogen Sulphide is removed by Gas Scrubbing unit. Sewage rising in the reactors are taken to Facultative Aerated Lagoon (FAL) for aeration. 24 Aerators of 50 HP capacity will be operated out of 30 Aerators and resulting induction of oxygen (1.8 Kg/Kw/Hr) will reduce the BOD Load by further 75% HRT in FAL is 24 Hours. Area of FAL Hectares. Sewage is then led to Polishing Pond (Area = 9.0 Hectares) with 3 baffle walls to increase the length of flow with a HRT of 12 Hours, where any remaining suspended solids are removed. Disinfection using chlorine is done before discharging the treated effluent to river Musi. LITERATURE REVIEW Proposed Treatment Process Montgomery Watson then known as Associated Industrial Consultants prepared a Conceptual Design Report in November 1993 under Rehabilitation and strengthening Program of the Sewerage System in Hyderabad. Technoeconomical evaluation of various options was carried out and presented in the report. It was concluded that the sewage treatment scheme consisting of primary units, UASB reactors followed by facultative type of Aerated Lagoon (FAL) was most suitable for sewage treatment in the context of Hyderabad. In the year 2000, NRCD included a new guideline for the discharge of treated sewage into river or for its use on agricultural fields.

2 N RAMA KRISHNA, et al, [IJRSAE] TM The parameter included is concentration Fecal Coliform in the wastewater. According to this guideline fecal coliform present in the treated wastewater 12 shall be less that 10,000 MPN/100ml of sample. To achieve these new standards chlorination is suggested for the effluent of FAL before its discharge. Chlorinating is found economically better solution when compared to the other mode of disinfecting i.e. UV Radiation. During the period 1969 to 1981 the American Water Works Association (AWWA) Research Foundation and the AWWA Sludge Disposal Committee prepared a series of reports with a comprehensive literature review on the nature and solutions of water treatment plant waste disposal problems. The first report, prepared by the AWWA Research Foundation, was divided into four parts (AWWA Research Foundation, 1969a, 1969b, 1969c, 1970) and was entitled "Disposal of Wastes from Water Treatment Plants." The first part of this report (AWWA, 1969a) covered the status of research and engineering practices for treating various wastes from water treatment plants. The second part (AWWA, 1969b) reviewed plant operations for the disposal of various types of wastes, and the regulatory aspects of disposal. The third part (AWWA, 1969c) described various treatment processes employed and their efficiency and degree of success, and presented cost analyses. The last part (AWWA, 1970) summarized research needs, engineering needs, plant operation needs, and regulatory needs. 2.1 CONVENTIONAL WASTEWATER TREATMENT PROCESSES Sewage Treatment Plant is a facility designed to receive the waste from domestic, commercial and industrial sources and to remove materials that damage water quality and compromise public health and safety when discharged into water receiving systems. Objective: - The Principal objective of waste water treatment is generally to allow human and industrial effluents to be disposed of without danger to human health or unacceptable damage to the natural environment. Conventional wastewater treatment consists of a combination of Physical, chemical, and biological processes and operations to remove solids, organic matter and, sometimes, nutrients from wastewater. Preliminary Treatment The objective of preliminary treatment is the removal of in organic material, coarse solids and other large materials often found in raw wastewater. Removal of these materials is necessary to enhance the operation and maintenance of subsequent treatment units. Preminary treatment operations typically include coarse screening, grit removal and, in some cases, communication of large objects. A.Primary Treatment The objective of primary treatment is the removal of settleable organic and inorganic solids by sedimentation, and the removal of materials that will float (scum) by skimming. B.Secondary Treatment The objective of secondary treatment is the further treatment of the effluent from primary treatment to remove the residual organics and suspended solids. In most

3 N RAMA KRISHNA, et al, [IJRSAE] TM cases, secondary treatment follows primary treatment and involves the removal of biodegradable dissolved and colloidal organic matter using aerobic biological treatment processes. Aerobic biological treatment is performed in the presence of oxygen by aerobic microorganisms (principally bacteria) that metabolize the organic matter in the waste water, thereby producing more microorganisms and inorganic endproducts (principally CO2, NH3, and H2 O). Several aerobic biological processes are used for secondary treatment differing primarily in the manner in which oxygen is supplied to the microorganisms and in the rate at which organisms metabolize the organic matter. Common high-rate processes include the activated sludge processes, trickling filters or bio filters, oxidation ditches, and rotating biological contractors (RBC). A combination of two of these processes in series (e.g. bio filter followed by activated sludge) is sometimes used to treat municipal wastewater containing a high concentration of organic material from industrial sources SEWAGE/ WASTE WATER TREATMENT TECHNOLOGIES 1.Activated Sludge Process The most common suspended growth process used for municipal wastewater treatment is the activated sludge process. The municipal wastewater treatment is the BOD-removal. The removal of BOD is done by a biological process, such as the suspended growth treatment process. This biological process is an aerobic process and takes place in the aeration tank, in where the wastewater is aerated with oxygen. By creating good conditions, bacteria will grow fast. The grow of bacteria creates flocks and gases. These flocks will removed by a secondary clarifier. In the activated sludge process, the dispersed-growth reactor is an aeration tank or basin containing as suspension of the wastewater and microorganisms, the mixed liquor. The contents of the aeration tank are mixed vigorously by aeration devices which also supply oxygen to the biological suspension. Aeration devices commonly used include submerged diffusers that release compressed air and mechanical surface aerators that introduce air by agitating the liquid surface. Hydraulic retention time in the aeration tanks usually ranges from 3 to 8 hours but can be higher with high BOD5 wastewaters. Following the aeration step, the microorganisms are separated from the liquid by sedimentation and the clarified liquid is secondary effluents. A portion of the biological sludge is recycled to the aeration basin to maintain a high mixed-liquor suspended solids (MLSS) level. The remainder is removed from the process and sent to sludge processing to maintain a relatively constant concentration of microorganisms in the system. Several variation of the basic activated sludge process, such as extended aeration and oxidation ditches, are in common use, but the principal are similar: 2.Trickling Filters A trickling filter or biofilter consists of a basin or tower filled with support media such as stones, plastic shapes, or wooden slats. Wastewater is applied intermittently, or sometimes continuously, over the media. Microorganisms become attached to the media and form a biological layer or fixed film. Organic matter in the wastewater diffuses into the film, where it is metabolized. Oxygen is normally supplied to

4 N RAMA KRISHNA, et al, [IJRSAE] TM the film by the natural flow of air either up or down through the media, depending on the relative temperatures of the wastewater and ambient air. Forced air can also be supplied by blowers but this is rarely necessary. The thickness of the biofilm increases as new organisms grow. Periodically, portions of the film 'slough off the media. The sloughed material is separated from the liquid in a secondary clarifier and discharged to sludge processing. Clarified liquid from the secondary clarifier is the secondary effluent and a portion is often recycled to the biofilter to improve hydraulic distribution of the wastewater over the filter. 3.Rotating Biological Contactors Rotating biological contactors (RBCs) are fixed-film reactors similar to biofilters in that organisms are attached to support media. In the case of the RBC, the support media are slowly rotating discs that are partially submerged in flowing wastewater in the reactor. Oxygen is supplied to the attached biofilm from the air when the film is out of the water and from the liquid when submerged, since oxygen is transferred to the wastewater by surface turbulence created by the discs rotation. Sloughed pieces of biofilm are removed in the same manner described for biofilters. High-rate biological treatment processes, in combination with primary sedimentation, typically remove 85 % of the BOD5 and SS originally present in the raw wastewater and some of the heavy metals. Activated sludge generally produces an effluent of slightly higher quality, in terms of these constituents, than biofilters or RBCs. When coupled with a disinfection step, these processes can provide substantial but not complete removal of bacteria and virus. However, they remove very little phosphorus, nitrogen, non-biodegradable organics, or dissolved minerals. 4.Upflow Anaerobic Sludge Blanket (UASB) Process UASB is an anaerobic process whilst forming a blanket of granular sludge and suspended in the tank. Wastewater flows upwards through the blanket and is processed by the anaerobic microorganisms. The upward flow combined with the settling action of gravity suspends the blanket with the aid of flocculants. The blanket begins to reach maturity at around 3 months. Small sludge granules begin to form whose surface area is covered in aggregations of bacteria. In the absence of any support matrix, the flow conditions create a selective environment in which only those microorganisms, capable of attaching to each other, survive and proliferate. Eventually the aggregates form into dense compact biofilms referred to as "granules". How does the UASB reactor Work? Fine granular sludge blanket acts as a filter to prevent the solids in the incoming wastes to flow through as the liquid part does. So if the hydraulic retention time (HRT) does not change, which is limited to 1-3 days (the bigger the Reactor, the shorter time it is, because the size costs money), the solid retention time (SRT) can be days or more for more effective digestion, depending on the shape of the digestion chamber. It means that the digester becomes much more efficient without having to increase the size, which costs money. Wageningen University in the Netherlands has started to do R & D along these lines. Standing and hanging baffles are used, with a conic separation with a small outlet at the center will be much more effective to keep the anaerobic sludge blanket in the lower

5 N RAMA KRISHNA, et al, [IJRSAE] TM part of the digester. This will act as a very good filter to retard the flow of solids in the wastes and prolong the solid retention time for more bacterial action. However, the digester will be more economic if the loading can be increased for a specific size of digester with the conic separation. COD reduction of 58% now obtained is adequate, and no attempt should be made to increase the bacterial action at such high costs. It is better to use much cheaper open tanks and basins for more effectiveness and efficiency, as in the IF&WMS(Integrated Farming And Waste Management System). Bio-Chemical Activities in USAB Reactors Bacterial actions are in 3 phases in the digester and they occur IN SEQUENCE: 1.Hydrolysis Or Solubilization - The first phase takes days, and until the complex organics are solubilized, they cannot be absorbed into the cells of the bacteria where they are degraded by the endoenzymes; 2 Acidogenesis Or Acetogenesis - The result from stage one utilized by a second group of organisms to form organic acids; 3 Methanogenesis - The methaneproducing (methanogenic) anaerobic bacteria then use the product of (2) to complete the decomposition process. 5. Waste Stabilization Ponds for Wastewater Treatment STANDARD FOR TREATED SEWAGE FOR DISCHARGE Introduction WASTE WATER STABILIZATION POND TECHNOLOGY IS ONE OF THE MOST IMPORTANT NATURAL METHODS FOR WASTEWATER TREATMENT. WASTE STABILIZATION PONDS ARE MAINLY SHALLOW MAN-MADE BASINS COMPRISING A SINGLE OR SEVERAL SERIES OF ANAEROBIC, FACULTATIVE OR MATURATION PONDS THE PRIMARY TREATMENT TAKES PLACE IN THE ANAEROBIC POND, WHICH IS MAINLY DESIGNED FOR REMOVING SUSPENDED SOLIDS, AND SOME OF THE SOLUBLE ELEMENT OF ORGANIC MATTER (BOD). DURING THE SECONDARY STAGE IN THE FACULTATIVE POND MOST OF THE REMAINING BOD IS REMOVED THROUGH THE COORDINATED ACTIVITY OF ALGAE AND HETEROTROPHIC BACTERIA. THE MAIN FUNCTION OF THE TERTIARY TREATMENT IN THE MATURATION POND IS THE REMOVAL OF PATHOGENS AND NUTRIENTS (ESPECIALLY NITROGEN). WASTE STABILIZATION POND TECHNOLOGY IS THE MOST COST-EFFECTIVE WASTEWATER TREATMENT TECHNOLOGY FOR THE REMOVAL OF PATHOGENIC MICRO-ORGANISMS. THE TREATMENT IS ACHIEVED THROUGH NATURAL DISINFECTION MECHANISMS. IT IS PARTICULARLY WELL SUITED FOR TROPICAL AND SUBTROPICAL COUNTRIES BECAUSE THE INTENSITY OF THE SUNLIGHT AND TEMPERATURE ARE KEY FACTORS FOR THE EFFICIENCY OF THE REMOVAL PROCESSES PARAMETERS INTO WATER BODY ON LAND BOD(mg/l)

6 N RAMA KRISHNA, et al, [IJRSAE] TM TSS (mg/l) FAECAL COLIFORM (MPN/100 ml) 1000 (Desirable) (Maximum) LABOTATORY TESTING OF TREATED SEWAGE S.NO PARAMETERES APPARATUS 1 PH PH METER 2 TEMPERATURE DO METER 3 DISSOLVED OXYGEN DO METER 4 SUSPENDED SOLIDS SPECTRO PHOTOMETER 5 VOLATILE SUSPENDED SOLIDS MUFFEL FURNANCE 6 COD TOTAL DIGESTION APPARATUS 7 COD FILTER DIGESTION APPARATUS

7 N RAMA KRISHNA, et al, [IJRSAE] TM 8 BOD TOTAL INCUBATION APP 9 BOD FILTER INCUBATION APP 10 ALKALINITY TITRATION 11 SULPHATE SPECTRO PHOTOMETER 12 SULPHIDE SPECTRO PHOTOMETER 13 VOLATILE FATTY ACIDS SPECTRO PHOTOMETER 14 FEACOL COLIFORM INCUBATOR

8 N RAMA KRISHNA, et al, [IJRSAE] TM SITELAYOUT

9 N RAMA KRISHNA, et al, [IJRSAE] TM SCHEMETICFLOW 4.1 CONCLUSION The ultimate goal of wastewater management is the protection of the environment in a manner commensurate with public health and socio-economic concerns. Based on the nature of wastewater, it issuggested whether primary, secondary and tertiary treatment will be carried out before final disposal. Understanding the nature of wastewater is

10 N RAMA KRISHNA, et al, [IJRSAE] TM fundamental to design appropriate wastewater treatment process, to adopt an appropriate procedure, determination of acceptable criteria for the residues, determination of a degree of evaluation required to validate the procedure and decision on the residues to be tested based on toxicity therefore, it is necessary to ensure the safety, efficacy and quality of the treated wastewater. The project" structural and operational study of 339 MLD capacity Sewage Treatment Plant at Amberpet" include the performance of each unit based on the extent of treatment done at the plant. As per the data available at site and physical observation, a conclusion that the plant was running smoothly and the required efficiency of treatment is achieved for safe disposal of sewage into Musi River as per the norms of river standards. Important parameters before disposal into River Musilike BOD, Suspended solids, COD, Fecal Coli-forms are within the design limits. REFERENCES WATER SUPPLY AND SANITARY ENGINEERING G.S BIRIDIE, JS BIRIDIE 4.2 FUTURE SCOPE OF WORK The Grit removed from Detritor tank may be utilised for alternate to sand after washing mechanically and may be directly used for land filling. The generated sludge cake may be used as manure as NPK values are sufficient in sludge cake. Due to traces of some heavy metals in sludge, cake it is unacceptable, and it is required to study extensively for reduction in concentration of heavy metals. Awarding carbon credits to this plant. The power generated which is currently being used internally was to put before UNFCCC and there is possibility of monetary credit benefit for the organisation. The out let channel of plant which joins River Musi has 10 m head. This head can be utilised for generation of Hydel power.