GB2062604A - Liquid waste treating apparatus - Google Patents

Abstract

A liquid waste treatment apparatus comprises a tank for containing the liquid waste, inlet means for a silicate setting agent, means for mixing the setting agent and the waste, an outlet nozzle tor the mixed waste and setting agent, a vessel for containing silicate solution in communication with the outlet nozzle and means at or near the outlet nozzle for mixing the silicate solution with the mixture of waste and setting agent.

Description

SPECIFICATION Waste treating apparatus This invention relates to a mobile apparatus for the treatment of liquid waste.

The disposal of liquid waste by industrial plants presents a problem because the waste should be disposed of in such a manner that it does not pollute the environment, and yet at a cost that is not too great. The dumping of waste into rivers and other bodies of water is now prevented to a large extent and many industries have built ponds or lagoons, to which they deliver the liquid waste.

Such a system is not entirely satisfactory because the waste sometimes breaks out of its confinement, due to dike failure and substrate seepage, and large areas of land are required for the holding ponds. One solution to the disposal problem is to remove the liquid waste or sludge from the ponds, mix it with an alkali metal silicate and a setting agent such as Portland cement and then pump it out onto land of little value where the waste immediately or in a very short time solidifies into a dirt-like material in which the pollutants are trapped. This waste material meets environmental standards and can be used as land fill.Since, in the case of large volumes, it would be very expensive to transport the liquid waste from the holding ponds to a central treatment plant and then carry the treated material to a disposal area, it is highly desirable to be able to transport the treatment equipment to the source of waste, the ponds, and/or the disposal areas.

The invention seeks to provide a simple and economical mobile apparatus which can be filled at the source of the waste and discharged at a desired disposal area.

According to the present invention there is provided an apparatus which comprises a tank for containing liquid waste, inlet means for silicate setting agent, mixing means for mixing the setting agent with the waste, a vessel for containing silicate solution in communication with an outlet nozzle for the mixed waste and setting agent, and means at or near the outlet nozzle to mix the silicate solution with the waste and setting agent.

The means for mixing the setting agent with the waste may be any suitable mixing blades, and is preferably an auger. Ideally the inlet for the setting agent is adjacent the mixing means, and when the latter is an auger it may also serve the purpose of carrying the setting agent into the tank as well as mixing it with the liquid waste.

The outlet nozzle can be connected to the tank by a suitable conduit and will be located in a convenient position for discharging the treated waste to a disposal area. The silicate solution is preferably injected into the oulet conduit near to the nozzle just before the means to mix the solution with the waste, which may be, for example, mixing blades, baffles, or the like. Since the setting time for the mixture once the silicate has been added is short, possibly as low as 10 seconds, the silicate injection should be as close to the nozzle as possible.

The apparatus of the invention is intended to be carried, e.g. on a lorry, or may be fitted with wheels and towed as a trailer. One of the advantages of the apparatus is that it is not restricted to operation near a source of waste product, but may be filled, for instance at a factory, and taken to a disposal area possibly many miles away where the waste is treated and discharged. It can eliminate the need for a central waste pond, and can be operated by one man acting as a driver/operator.

The invention will be described further, by way of example, with reference to the accompanying drawings, in which: Figure 1 is side elevational view, partly in section, of an apparatus constructed according to the invention; Figure 2 is a partial plan view of the apparatus of Figure 1; Figure 3 is a diagrammatic end view of the apparatus of Figure 1; Figure 4 is an enlarged view, partly in section, of one form of silicate mixing means; Figure 5 is top view of the mixer of Figure 4; Figure 6 is a similar to Figure 4 of an alternative mixer; Figure 7 is a top view of the mixer of Figure 6; and Figure 8 is partial side elevational view of an outlet nozzle.

Referring mainly to Figures 1 to 3, the treatment apparatus 10 comprises a tank 12 mounted on a chassis 14 provided with wheels 16 and adapted to be towed behind a vehicle. The tank may be fitted with liquid waste from the top or through an inlet coupling 18. Silicate setting agent, for example Portland cement, can be introduced through inlet means comprising an inlet pipe 20, having a valve 22, connected to suitable hopper (not shown). The inlet pipe 20 opens into an induction chamber 24 which partly encloses an auger or Archimedes screw 26 which serves not only to carry the cement into the waste but also to effect thorough mixing of the two. The auger 26 is externally driven via a shaft 28 passing through a seal and bearing arrangement in the end of the tank 12. The cement may be inducted by using compressed air, or by reducing the pressure within the tank 12.

A vessel 30 is mounted on the tank 12 to hold the silicate solution, usually sodium silicate, and is connected via a conduit 32 and a valve 34 to a mixer unit 36, such as that shown in Figures 4 and 5. The coupling 18 also couples the slurry in the tank 12 with the mixer unit 36, and such slurry flows in the direction of arrow 'A' in Figure 4. The mixer has a centrally disposed turbine 38 coupled with mixing blades 40 on a common shaft 42.

Passage of the slurry turns the turbine and hence the mixing blades 40. The silicate conduit 32 connects with a pair of silicate discharge tubes 44 which inject silicate solution into the slurry just upstream of the mixing zone 46. From the mixing zone 46 the mixture passes to an outlet nozzle 48 (Figure 8) which, as illustrated, is provided with a baffle plate 50 which has the effect of spraying the mixture in all directions rather than directing it in a solid stream. As the mixture often gels or solidifies before it reaches the ground, this is advantageous.

In operation, the tank 12 is filled with liquid waste, e.g. dyehouse effluent, and the apparatus towed to a disposal area such as a tip or landfill area. There the auger drive is connected to a power source, e.g. the towing vehicle power take off shaft, and Portland cement is sucked in through the inlet pipe 20 and mixed with the waste by means of the auger 26 to form a slurry. A compressor 52, driven from the auger drive, supplies compressed air which ejects the slurry through the coupling 18 towards the nozzle 48.

Compressed air is also fed to the silicate tank 30 forcing silicate solution along the conduit 32 and out of the discharge tubes 44 into the slurry. The silicate is thoroughly mixed with the slurry in the zone 46 and the mixture exits through the outlet nozzle 48. The setting time of the mixture may be as little as 4 to 6 seconds to form a soft solid, and after some further time it hardens further to a clay or sand-like consistency when it is impervious to water. Consequently the silicate injection and mixing should be quick and efficient, and take place as near to the outlet nozzle as possible.In order to prevent the nozzle 48 blocking with residual solidified mixture after use, the valve 34 in the silicate conduit 32 may be operated, e.g. by means of a hydraulic ram 54, to shut off the supply of silicate solution shortly before the discharge of slurry is halted, thus ensuring that silicate-charged mixture if flushed from the system.

The ram may be arranged also to shut off a slurry valve 56 in the coupling 18 with a delay built into the ram linkage to shut off the silicate valve 34 in advance of the slurry valve 56.

The compressor 52 may be used in reverse to fill the tank 12 by lowering the pressure therein and causing the liquid waste to be sucked in, e.g.

through the coupling 18.

Figures 6 and 7 illustrate an alternative form or mixer. Slurry flows in the direction of arrow 'A' as before and there are silicate discharge tubes 44.

Swirl is imported to the slurry by means of a spiral throw plate 58 and suitably located baffles 60 cause turbulence and hence mixing. This form of mixer is simpler than that of Figures 4 and 5 and is less susceptible to clogging through foreign bodies in the waste, but is somewhat less efficient in mixing and hence requires a smaller ratio of waste: silicate/setting agent.

In a particular example an apparatus according to the invention was filled with 5,500 litres of flocced dye effluent, containing inter alia white spirit, and 500 kg of Portland cement was introduced by means of the auger, which was operated until an evenly mixed slurry was obtained. This was taken to a discharge area and discharged while metering 225 litres of sodium silicate solution into the mixing zone. On leaving the nozzle the mixture set to soft solid within 10 to 15 seconds. The amount of chemicals needed was substantially less than would be needed to operate the process without the apparatus of the invention, owing to the superior mixing of the latter.

The apparatus of the invention simple, reliable and economical, and enables troublesome liquid effluents to be disposed of in a non-polluting manner.

Claims (10)

1. An apparatus for the treatment of liquid waste which comprises a tank for containing the liquid waste, inlet means for a silicate setting agent, mixing means for mixing the setting agent with the waste, a vessel for containing silicate solution in communication with an outlet nozzle for the mixed waste and setting agent, and means at or near the outlet nozzle to mix the silicate solution with the waste and setting agent.

2. An apparatus as claimed in claim 1 in which the means for mixing the setting agent with the waste comprises an auger.

3. An apparatus as claimed in either of claims 1 or 2 in which the inlet for the setting agent is adjacent the mixing means.

4. An apparatus as claimed in claim 3 in which the mixing means is an auger which is capable of carrying the setting agent into the tank as well as mixing it with the liquid waste.

5. An apparatus as claimed in any one of claims 1 to 4 in which the outlet nozzle is connected to the tank by conduits.

6. An apparatus as claimed in claim 5 in which the silicate solution is injected into the outlet conduit near to the nozzle just before the means to mix the solution with the waste.

7. An apparatus as claimed in any one of claims 1 to 6 in which the means to mix the solution with the waste comprises mixing blades or baffles.

8. An apparatus as claimed in any one of claims 1 to 7 adapted to be carried on a vehicle.

9. An apparatus as claimed in any one of claims 1 to 7 fitted with wheels and adapted to be towed as a trailer.

10. An apparatus for the treatment of liquid waste substantially as hereinbefore described with reference to the accompanying drawings.