Acidic Water
Treatment
1.0 Basis of design
The plant is required to treat and discharge into the sewer effluent from a battery factory, which will discharge Sulphuric Acid and rinse water.
Discharge Limits
 | pH 6 to 9 |
| Total suspended solids 400 mg |
Should the above discharge limits vary for any reason, it may change the design.
We have based our design on the following assumptions:-
| Total acidic flow 25,000 liters. per hour with 3 grams per liter. of Sulphuric acid. |
| Total amount of acid is as follows:- |
| 25,000 x 3 = 75 kilos per hour of 100% Sulphuric acid 1,000 |
Reagent to be utilised is calcium hydroxide at approximately 10% concentration. It is presumed that re-agent will be available in a fine dry 100% concentrated powder and our calculations show a consumption of 700 kilos of powder per 8 hour shift.
2.0 Process description
The plant is designed to neutralise 250 m3 per day of waste water (from a lead acid battery plant) containing 3 g/1 of Sulphuric acid, at a maximum flow of 25000 liters. per hour. The neutralising reagent is calcium hydroxide. The waste water is received into an acid pit and is pumped from there into the first stage neutralisation tank. Pumping is by a positive displacement pump which runs until cut off by a low level probe. A high level probe switches on a standby pump when required.
The liquor in the first stage neutralisation tank is treated with calcium hydroxide. The flow of this re-agent is preset on a manual, diaphragm valve and a pneumatic valve opens to let in the re-agent whenever the acid pit pump runs. Operation of the standby pump opens a pneumatic valve in a second dosing point. The liquor is continuously stirred and overflow into the second stage neutralisation tank.
Control of pH in the second stage neutralisation tank is by pH feed back. When an acid pH is sensed, a pneumatic valve in a dosing line opens to allow calcium hydroxide into the tank. If the pH remains too acid after a preset time, a second valve opens in another dosing point to allow more re-agent in. The liquor is continuously stirred and overflow to a pumping tank which will transfer to settlement tank.
All pH corrected effluent will overflow into a pumping tank from which it is transferred automatically under level control to a lamina settlement tank. Design includes for a standby/boost pump which will automatically activate under level control.
All effluent entering the lamina settlement tank flow will be directed to the bottom of the rectangular up-flow tank, clear water will enter through the lamina plates and out onto the peripheral weir from which it will enter the discharge point or, if desired, recycle back to service.
All sludge accumulated on the bottom portion of the settlement tank will have to be, periodically, removed by opening an outlet valve located on the bottom of the cone portion of the tank, this sludge will have to be disposed of either by road tanker or some other means. Our quotation does not include for any further treatment but if required this can be incorporated.
3.0 Reagents
Calcium Hydroxide re-agent would be handled as follows:-
one make up which would be continuously stirred complete with level control, pipe work, valves etc. Tank would be complete with a pump to transfer the milk of lime to the next stage which is the dosing tank. This consists of a unit complete with stirrer, two pumps to transfer the re-agent in a recirculating loop which is drawn off automatically by the pH signal in the neutralisation stage 1 and 2.
4.0 Equipment specification
1. Acidic Sump
| One Reception balancing pit having a total volume of 27 cu. meters suitably constructed and lined against corrosion. Customer supply. |
| One Positive Displacement Pump manufactured from
stainless steel complete with all necessary inlet/outlet valves etc. suitable for 25 cu. meters per hour, 10 meters head. |
| One Positive Displacement Pump as per item 1.2. |
| One Manifold for above pumps, comprising of delivery valves, isolating valves and pipe-work and fittings. |
| One Geared stirrer manufactured from stainless steel
shaft, couplings and propeller, complete with a totally enclosed fan cooled motor. |
| One stirrer support manufactured from mild steel section
and suitable for locating across the pit. Support will be finished in hot dip galvanising. |
| One Double level probe system for automation of pumps
and stirrers (low level cut out and flood warning). Complete with necessary supports for
locating on pit. |
Approximate size 3.2 meters dia. x 3 meters high.
| One Stirrer manufactured from stainless steel shaft and complete with totally enclosed fan cooled motor. |
One Dosing comprising.:-
| One 1" pneumatic valve |
| Two 1" diaphragm valves |
| Two transparent connectors - to see dosing taking place |
One Drain valve manufactured from PVC size 25mm dia.
One pH probe complete with glass electrode.
3. Second Stage Neutralisation
Unit is to be identical to item 2 with the exception of the dosing which is as follows:-
| One Dosing comprising:- |
| Two 1/2" pneumatic valves |
| Three 1/2" diaphragm valves |
| Three inspection pipes |
4. Pumping Tank
| One Pumping tank 1.3 M3 capacity manufactured from carbon steel suitable painted internal and external with an epoxy material. Approximate size 1.4 meters dia x 1.3 meters high. |
| One Double level probe system manufactured from stainless steel and to give the following signals:- 1 - Low level (pump stops), 2- Flood alarm (starts second pump) |
| One Flooded suction pump manufactured from cast iron with a totally enclosed fan cooled motor and suitable for 25 cu. meters per hour at 10 meters head. |
| One Standby pump as per item 4.3. |
| One Pump manifold complete with isolating valve, strainer, non-return valves, flow regulating valves and all necessary pipe work and fittings. |
| One Drain valve manufactured from PVC 25 mm id. and complete with overflow paperwork. |
5. Lamina Settlement Stage
One Lamina settlement tank manufactured from carbon steel having a volume of approximately 27 cu. meters complete with manual dislodging valve. Unit would be painted with red oxide externally, bitumen internally and is complete with lamina sheets.
Approximate size 3 meters x 2.2 meters 4 meters overall height.
6. Lime Re-Agent
Re-agent consists of two tanks, one for the make-up of the re- agent and the other for the dosing of the re- agent which is as follows:
| One Make-up re-agent module 7.5 cu. meters capacity manufactured from carbon steel, painted externally to suit customer requirements. Approximate size 2.3 meters dia. x 1.8 meters high. |
| One Direct drive stirrer manufactured from stainless steel shaft propeller and complete with a totally enclosed fan cooled motor. |
| One Self priming pump manufactured from cast iron and complete with a totally enclosed fan cooled motor. |
| Duty - 5 meter cu. per hour located on top of the tank for the transfer of the milk of lime re-agent to the dosing tank/neutralisation. |
One Single level probe system manufactured from PVC and to give the following signals:-
| One set All necessary pipe work and fittings required for the transfer of the re-agent. |
| One Drain valve manufactured from PVC 25 mm dia complete with overflow pipe work. |
| One Re-agent tank 7.5 cu. meter capacity as described under item 6.1. |
| One Stirrer manufactured from stainless steel shaft and propeller, complete with a totally enclosed fan cooled motor. |
| One Self priming pump manufactured from cast iron and complete with a totally enclosed fan cooled motor. |
| Duty - 5 cu. meters per hour at 20 meters head located on top of the tank. |
| One Pump manifold complete with all necessary valves, pipe work and fittings. |
| One Drain valve manufactured from PVC 25 mm dia. complete with overflow pipe work. |
7. Instrument Control Console
One Instrument control console incorporating treatment and instrumentation consisting of:-
| 2 - pH meters |
| 9 - Level controllers |
| 12 - Motor starters, complete with auto-off-manual switches, alarm warning lights, audible alarms, relays etc. fully wired for operation. |
8. Interconnecting Pipe work
8.1 One set Pipe work and fittings required to inter-connect all the above equipment. It is presumed that all our plant will be located together in a closed and tidy site.
9. Cable and Conduit
One set Cable and conduit required to interconnect our control console to various items of our supply within the plant. It is presumed that the plant is located together in a tidy site.
10. Erection and Commissioning
All necessary positioning, commissioning, and interconnecting, customer supply.
11. Documentation
The following documentation is included in the offer price.
| Fully detailed flow sheet |
| Fully detailed plant layout |
| Outlined drawings of civil engineering works |
| Schematic wiring diagram of control console |
| External wiring diagram showing the connections between control console and electrical items within the effluent plant. |
| Fully detailed pipe work layout |
| Instruction manual |
12. Limits of Supply
Tender includes only those goods and services specified herein. For information only we list some items which are not included in the above tender price. It is not to be construed that this list is necessarily comprehensive:-
| Supply or detailed design of civil engineering works, including foundation pits, gulleys etc. |
| Supply of pipe work unless otherwise stated. |
| Supply, design and distribution of services to the whole of our plant. Services required are as follows:- |
Electrical supply - 380 volts 3 phase 50 cycles. Transformer will be supplied in our control console for the required 24 volt control gear. Water supply - 20 cu. meters per hour with 4 kg per cm2
| Compressed air supply of approximately 1.7 cu. meters per minute at 7 bar. |
| Supply of chemicals for the neutralisation of effluent. |
| Frost protection if required. |
| Supply of labour for all electrical equipment required for the wiring of all our materials. |
| Possible required raised platforms for access to re-agent tanks and neutralisation modules. |