Effluent Treatment Plant

KASUR TANNERIES POLLUTION CONTROL PROJECT (KTPC) - A DOCUMENTARY


LOCATION AND AREA The effluent treatment plant is located on the Dipalpur road and almost 3 Km from the main city. The total area of the plant is almost 62 acres.


COLLECTION SYSTEM The purpose of collection system is to collect the effluent from all of the four clusters (Dingarh, Younas Nagar, Kot Abdul Kadir, and Niaz Nagar), in a common tank and then supply it to the common effluent treatment plant. The effluent from the Younas Nagar and Dingargh is collected through the pumping station whereas the gravity flow is used for the other two clusters of tanneries. Coarse screens and grit chamber is installed for individual tannery to protect drainage from clogging with coarse, settling and floating materials. It will also help to cut off loading on the common effluent treatment plant. Flow meters are installed in the tanneries to make sure the economical use of the water in the process. COMMON EFFLUENT TREATMENT PLANT The common effluent treatment plant is the common facility to treat the total effluent discharge from all of the four clusters of tanneries.


The plant has following major components: § Screens § Equalization tanks § Clarifiers (Settling tank) § Effluent treatment lagoons § Permanent sludge lagoons The effluent is treated in four major steps in the plant. These steps are as follows: 1. Screening The effluent is screened at the first stage. The screens are fitted in the channels, made of silicon resisted cement. The property of this cement is that it will resist any erosion effect. The manually cleaned coarse screen is made up of stainless steel SS316 having the mesh size of 50mm. The maximum flow through the screen can be 980 m3/h. the screen has a gradient of 700 with the horizontal. The raw form of the fleshing and suspended solids larger than 50 mm size will be screened out at this stage. After it the automatically cleaned fine screening is done. The fine screen is made up of same material but has the mesh size of 6mm. The fine screen is automatically controlled through a control unit in the screen house. The max. flow through the screen cannot be more than 980 m3/h. The building area of screen house is 12 by 5 m and height is 3.5 m. The purpose of the screening is to remove the heavy pieces of flesh, hair and skins from the effluent. The by-pass channels are provided to divert the passage of flow of effluent to equalization tank. It is required when the screens are to be cleaned and serviced. The alternative path contains similar screens. The flow is regulated with the help of the flow gates. Flow gates are made of the SS316 and are manually operated. 2. Storage The effluent after screening is supplied to equalization tank. They are two in number and have the maximum capacity of 12,700 cubic meter.


The purpose of equalization tank is to store the effluent for 24 hours. The effluent is mixed with the help of aerators. The purpose is to homogenize the suspended particles concentration through the effluent. The aerators also provide to lower the BOD of the effluent. Sixteen aerators in total will be installed for two equalization tanks, they are surface type aerators suspended through cables. Aerators are imported equipment from Australia provided through technical assistance of UNDP. The equalization tank is made of silicon resistant cement having dimensions 65 by 32.5 meters and 3 meters working depth. The slope of 3 mm in 1 meter is provided to assist the gravity flow of effluent out of the tanks. The effluent then goes to the pump house. The aerators have following specifications: § Power 30KW § Oxygen transfer 1.8 kg O2/kWh § Overall mixing power 38 W/m3 § Oxygen required for sulfide oxidation 0.75 kg O2/kg S-2


The pump has three pumps of 350 cubic meter per hour discharge capacity. Out of these three one will be used in emergency operations. The pumps are made by A.B.S. 1. Settling Tanks The pumping station will pump the effluent into sedimentation tanks where the coagulation process will be carried out. The coagulant used will be lime (sodium carbonate Na2 CO3). Coagulation is followed by primary sedimentation. Due to the coagulation, the flocs are produced which coalesce with each other to form thick sludge. The sludge will eventually settle down at the bottom of tank. The sludge is mechanically separated from effluent in settling tank by equipment called 'scraper'. The effluent is


discharged from the top weirs at the periphery of the tank. The settling tank is 18 meter in diameter and has working depth of 2.5 meter. The settling tank has the retention time of 2.5 hrs. The total volume being 611 m3.


The effluent is then passed to effluent treatment lagoons for further treatment and the sludge is dumped into permanent sludge lagoons. 4. Effluent Treatment Lagoons The effluent is filled in effluent treatment lagoons where it is biologically treated to lower down the BOD of the effluent. The oxygen from the air is allowed to react with dissolved particles. The oxidation will take place and particles will settle down. For this purpose sufficient is required and that's why effluent will remain in lagoons for 5 to 6 days before it is discharged.


There are 16 lagoons in total of 112 by 30 by 1.5 meter in dimensions. There are made up of compacted local soil under, which is the layer of clay having plasticity index PI ³ 14 and having the liquid limit of 35. Under clay is the layer of 1 mm high density polyethylene. The last layer is of geo membrane. 5. Permanent Sludge Lagoons The permanent sludge lagoons are space where the sludge from the settling tank is treated. The sludge, which already contains a high content of water, is then separated from water on drying beds. The process is quite similar to the settlement. The supernatant thus obtained is supplied back in equalization tanks through special piping and pumping arrangement. The permanent sludge lagoons are similar to effluent treatment lagoons in construction. They are two in number having dimensions 250 by 59 by 2.5 meters having life of 20 years.


6. Final OutFall The water after treatment is useable for any purpose will be discharged into Pandoki Drain through final outfall. The final outfall is made 1.78 Km open drain of 3 meter width and 5.88 Km sewer line 54 inches wide. The water will finally go into Sutlej River. SOLID WASTE DISPOSAL SITE The sole purpose of this site is to dispose off the solid waste generated from the tanneries. It is located on 2.2 Km long approach road. The solid waste has the average life of 15 years. The local municipal corporation will dump the solid here. The dimension of the site is 750 by 64 by 2 meters.


The plant also incorporates the following facilities: § Sub-station room § Generator room ( 694 kV electric generation capacity ) § Workshop § Offices ( main building ) § Tube well ( 6oo ft. working depth )