Surface World April 2019 Surface World April 2019 - Page 58

WATER & EFFLUENT TREATMENT and reduce the contact time that the chemical reagents require during pH neutralisation. As the treatment tank and the high speed industrial mixer have been designed and assembled here at our Stafford factory we can ensure that all the constituent parts are working together as efficiently as possible. The high speed mixer is supported by the fabricated mixer bridge and the shaft and propellor have been designed to ensure that they accommodate the volume of liquid in the tank and the dimensions of the whole fabrication. To help matters further, the location of the mixer bridge ensures that when not operational, the half access lid can easily be opened for maintenance, cleaning and inspection. The TM2 high speed industrial mixer is ideal for applications such as the pH neutralisation of wastewater. By creating a vortex within the tank the chemical reagents dosed from the dosing pumps are forced through the waste water to give good distribution. Combining good and even mixing along with a pH controller offering PID control as well as proportional control dosing pumps - the customer can be confident in both the waste-water treatment process and that chemical reagents aren’t being needlessly dosed into the system. Dosing Pump One key component of the waster water treatment is for pH neutralisation to occur. The customer’s processes generate effluent on either the acidic or alkaline side of the pH scale, depending upon which combination of processes are operating during their production process. The waste-water treatment system is able to neutralise the pH of the incoming effluent if it’s on the acid end of the pH scale or the alkaline end, thanks to the system being able to dose from one of the two chemical dosing pumps. Working with an incoming signal from the tank mounted PS90s pH electrode assembly and the P7687 PID pH controller - the pH controller sends a signal to either the acid dosing pump or the caustic dosing pump. Each of the pumps are our AT4-AM proportional dosing pump series with wetted parts suitable for each chemical reagent. With a maximum output of 60 Litres / Hour each, the AT4-AM dosing pumps can be automatically speeded up or slowed down by the pH controller to ensure that just the right amount of chemical reagent is dosed into the process to neutralise the pH. 56 APRIL 2019 Suction Lance Assembly The suction lance assembly fitted to each of the chemical dosing pumps allows for easy manual handling of the chemical containers, and when operational, maintains the prime of the dosing pumps. The integrated low level float switch also provides a signal to the control panel which can prevent the unit from operating when the chemical reagent has been used. To ensure that operator is aware that an alarm condition has been entered, an audible alarm sounds; the alarm beacon is illuminated and the corresponding low chemical level indicator is illuminated on the front of the panel. A remote alarm connection is also included for the customer for integration into their internal process system so that they are aware that the chemical needs to be replenished to ensure the pH neutralisation system can resume correct operation. The pH neutralisation system uses model AC.LA.25A suction lances specifically designed for use with 25 litre chemical containers. The suction lance is placed into the container aperture with the lid removed. The suction lances can be located within the chemical container by using the adjustable mounting flange, which also creates a seal over the opening. Using suction lance assemblies combined with the chemical containers being placed in the bunded area of the enclosure, which in turn is located behind a transparent cover plate - ensures that chemical handling risks are minimised where possible. Changing the chemical container once the chemical has been used is simple, as the suction lance assembly can easily be lifted out from the empty vessel, and placed into the new vessel once it’s securely positioned into the bund. As well as assisting in the handling of the chemical reagents, each suction lance assembly includes an integral non-return valve to help ensure that the pump remains primed. Air Operated Diaphragm Transfer Pump As the customers’ effluent is collected in a sump arrangement located underneath the water treatment system, it has to be transferred to the dosing tank for pH correction. Contained within an enclosure, complete with a front mounted transparent cover are two double diaphragm pneumatic pumps which are ideal for the job. With wetted parts in polypropylene and PTFE the double diaphragm pneumatic pumps are resistant to the chemistry used in the customer’s processes. The control panel controls two solenoid valves which in turn control the air flow to the pumps, allowing them to be automatically turned on, based on the incoming signal from sump mounted float switches. The double diaphragm pneumatic pumps are arranged in a duty and assist formation, with the assist pump being switched on when the customer’s processes generate enough waste water to require the addition of the second transfer pump. The air operated double diaphragm pumps used were the AWE models PP50’s with 1/4” outlets and maximum flow rates of 50 Litres / Minute. There are many advantages that are available when using an air operated double diaphragm pump to transfer waste water, effluent or even chemical reagents. They offer exceptional flow rates which can be easily adjusted by using an air regulating valve. In addition - with relatively simple construction, the diaphragm can be easily removed and cleaned for periodic maintenance, and they are of simple design and proven construction meaning that there really is very little to go wrong with them. pH Neutralisation System Commissioning Following the customer briefing and the approval of the designs, the process of completing the fabrications, assembly and control panel build were completed within 6 weeks. As the plant was designed to be skid mounted, loading on to a flat bed truck for same day delivery, and then positioning the pH neutralisation system to it’s site location was a relatively simple procedure. From the customers perspective, once the inlet and discharge pipework were connected, power brought onto the system - the pH neutralisation was ready for commissioning. The commissioning of the pH neutralisation system was completed by two of our Service Engineers within 7 weeks of us receiving the order from our customer. 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