Attachment_6_-_New_WSWPP_Process_Description.pdf

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Attachment 6 Wastewater Pretreatment Plant (WWPP) Chemical Treatment Process

New Wiping Solution Wastewater Pretreatment Plant (WSWPP)

PROCESS DESCRIPTION: The concentrate coming from the storage tank TK401 is sent to the treatment tank TK403, which is divided in two compartments. In the first one, where the effluent enters the tank until reaching the analog level LVA403EW2, the calcium chloride solution and the perlite are dosed, proportionally to the flow rate of screw pump PMV401. The effluent is kept stirred by mixer ST403A, operated by analog level LVA403EL.

Then the effluent gradually overflows to the second compartment, where the sulphuric acid is dosed, once reached the level control LVA403L, according to the pH-meter pH403 (set point range 7-8).

The effluent is continually stirred by mixer ST403B, operated by analog level

LVA403L.

The perlite is conveyed to the tank TK403, proportionally to the amount of concentrate from the tank TK401, by means of the motorized screw conveyor 432, whose speed is adjustable by the field inverter IN432 for flow rate adjustment.

The perlite addition is made by means of a motorized screw conveyor, inverter controlled, for which the frequency (or the rpm value) is proportionally linked to the flow rate of product; this system complies with the grade of accuracy required by the process.

The perlite, entering in TK403 through the pneumatic gate valve VL433, is stored in the stainless steel hopper TK406, equipped with the dust remover SC495, installed on top of it. This device is a self-cleaning filter connected to the blower 294.

The two automatic filter presses for recycling FP305 and FP405 operate by turn, so as to ensure the continuity of the production: when one of the filter reaches the end of cycle, meaning that its internal pressure reaches the saturation value (8-10 bars, adjustable via touch screen), and needs to be opened by the operator for sludge removal, the other can be started without affecting the process.

The pneumatic membrane pump PP301 (PP401), which feeds the filter press FP305 (FP405) via pneumatic ball valve PVC316 (PVC216), is actuated by the compressed air line through the 3-way proportional valve P3107 (PV407) by a feedback control loop based on the pressure value inside the filter press, as measured by the pressure transducer PS347 (PS447), installed together with the pressure gauge 346 (446) on the expansion vessel 345 (445).

A pressure regulator 802, a pressure gauge 308 (408) and a safety valve 311 (411) are also provided on the compressed air feeding line.

The filter press FP305 (FP405) is equipped with 60 PP filter plates by 800x800 mm and relevant PP filtering cloths.

It is also provided with a hydraulic power unit FP341 (FP441) to compact the plates at the required pressure as well as to open the filter press once reached the end of cycle: it also has a motorized plate shifting system FP342 (FP442) for sludge removal.

The sludge in form of cakes falls in proper containers placed beneath the filter frame.

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Before operating in production the automatic stand-by cycle makes the effluent circulate back to the second compartment of the feeding tank TK403 via pneumatic membrane valve PVO316B (PVO416B) for a preset time.

This represents the filtration warm-up (maximum 5 minutes) which properly distributes the pressure on the plate surface and removes impurities from the cloths before starting the production. Then the pneumatic membrane valve PVO316A (PVO416A) opens and the filtered effluent is sent to the storage tank TK501A until reaching the analog level control LVA501W2.

After reaching the pressure setpoint for the end of cycle, the system automatically activates a sludge dehydration phase by means of compressed air via pneumatic ball valve PVC316C (PVC416C); during this phase the liquid is sent back to tank TK403.

The piston metering pump PD403C1 (PD403C2 for treatment of waste solution occasionally contained in the emergency tanks TK100-100A) doses the calcium chloride solution directly from its supply drum via counter pressure valve VC403C; the flow rate of calcium chloride is read by the flow meter FM403C1 (FM403C2).

The proper amount of calcium chloride is preliminarily determined on the basis of the amount of suspended solids to get a proper flocculation (to be periodically checked).

The safety valve 735C intervenes activating a by-pass in case of overpressure in the feeding pipe and an alarm is activated by the mentioned flow meter.

The sulphuric acid storage tank TK480, equipped with analog level control LVA480 and mechanical overflow alarm LVM480, is fed by the relevant bulk tank via pneumatic ball valve PVC480.

The corresponding piston metering pump PD403A doses the sulphuric acid into the second compartment of treatment tank TK403 according to the pH-meter pH403 (set point range 7-8).

The safety valve 735A intervenes activating a by-pass in case of overpressure in the feeding pipe.

Finally, from tank 501A the filtered effluent is pumped to the treated solution tank TK501 by means of centrifugal pump PMC501A, activated by analog level LVA501AL until reaching LVA501W2.

The analog level activates the stirrer ST501 and the drain centrifugal pump

PMC501.

In case of treatment of the waste solution occasionally accumulated in the emergency tanks TK100-100A, the sulphuric acid is dosed into the tank TK501 by means of piston metering pump PD501A to correct the pH value according to the pH-meter pH503 before drain.

There is a service immersed pump available which can be used to recirculate the effluent back to the beginning of treatment in the unlikely event of a system up-set.

Moreover two manual valves will be mounted on the delivery of the pump PMC501A to give the possibility to divert the effluent back to TK403 or TK100.

PROCESS OPERATION: The Contractor shall operate the system with prudent engineering and operating practices. Operating the WSWPP includes, but is not limited to, the following tasks:

(1) The Contractor shall take readings every two (2) hours of the pumps data, Page 3 of 4 Pages flows, tank levels, data set points and operating conditions from the computer, and other set points throughout the system. It should be noted that in the future this may be at least partially performed by SCADA software.

(2) The Contractor shall perform an inspection of the system every two (2) hours or as often as needed for proper operation.

(3) The Contractor shall start, stop, empty filter presses, prepare the pallets, boxes, liners, fill each box to between >2,300 pounds and ≤ 2,400 pounds, band, properly label, and enter the data into the computer logging system which is furnished by the BEP, for the performance of this contract.

(4) The Contractor shall change/clean filter press filter cloths as needed when they become blinded or physically damaged.

(5) The Contractor shall mix the system materials as needed for the optimal operation of the system.

(6) The Contractor shall check pH set points, loop set points, and local set points; and calibrate pH meters weekly at a minimum or more often, as needed.

(7) The Contractor shall respond to all alarms, correcting the conditions to assure proper operation of the system.

(8) The Contractor shall clean and inspect the tanks at least annually as well as clean the tanks and affected equipment if there is a blockage (build-up) of sludge in any tank as necessary during the operation of the system.

(9) The Contractor shall order the materials/supplies as needed to assure continuous operation of the system.

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