This invention relates to a solids/liquid separator and more particularly the invention relates to a separator for separating floating and entrained bodies in liquid conduits, such as stormwater pipelines and channels.

Background of the Invention

Public concern over stormwater pollution has been heightened in recent years by the highly visible accumulations of litter and biodegradable matter despoiling urban beaches and waterways. The increase in these so-called "gross" pollutants (hereinafter referred to as gross pollutants) has been exacerbated by the adoption of non-biodegradable plastic, waxed materials and aluminium for takeaway food and beverage packaging.

Litter discarded in shopping centres and takeaway food outlets blows or washes into urban drainage systems that discharge to open water-bodies. During high flows, litter snags on shrubbery lining the banks of rivers and streams, presenting an aesthetically offensive appearance when the flow recedes . That portion that reaches bays and estuaries is driven ashore by prevailing winds and waves to remain stranded on beaches. Syringes often present in the litter are also a public health risk.

To mitigate the environmental damage and economic cost of these pollutants, drainage authorities frequently specify that gross pollutant traps (GPT ⁷ s) be installed in new urban shopping centre developments, urban sub-divisions and other types of building projects.

However experience with GPT' s has shown that if the biodegradable matter incidentally captured along with the

litter is held for long periods in the wet sumps of GPT' s, it will decompose and add to the pollution load in the receiving waters. When these types of GPT are pumped out the entire contents must be removed including the large volumes of contaminated water.

Summary of Invention

According to the present invention there is provided a separator for separating bodies from a liquid, the separator comprising a separator body through which liquid flows from a higher inlet port to a lower outlet port, the separator body including a bypass chamber, a separation chamber, a filter to remove bodies from liquid flowing through the separation chamber and a flow controller to control the flow through the separation chamber to the outlet port.

According to the present invention there is further provided a method of separating bodies entrained in a liquid flowing through a separator from a higher inlet port to a lower outlet port, including: diverting liquid entering the separator into a separation chamber; filtering bodies from liquid flowing through the separation chamber; and controlling the flow of liquid flowing through the separation chamber to the outlet; wherein at high flows liquid bypasses the separation chamber to flow to the outlet port.

Brief Description of the Drawings

One preferred embodiment of the invention will now be further described with reference to the following drawings in which:

Figure 1 is a plan view of a separator of the present invention with a ceiling removed;

Figure 2 is a side sectional view of a separator taken along the centre-line of the direction of a pipeline;

Figure 3 is a plan view of the separator taken at line A-A of Figure 2;

Figure 4 is an end sectional view of the separator taken at line B-B of Figure 2; and

Figure 5 is an end sectional view of the separator taken at line C-C of Figure 2.

Detailed Description of Preferred Embodiment

The separator shown in the Figures is designed to remove gross pollutants and other large matter from stormwater flows and to bypass excess flows without inducing energy- losses in the flow or causing loss of previously trapped matter. The separator may be installed in pipelines, open channels and other such conduits. Additionally, reference is made to use of the separator for stormwater treatment, but it is understood that the separator may be used for treatment of liquid other than stormwater including potable water, trade waste and sewage applications.

The present separator is a so-called "dry sump" that will prevent the decomposition of captured organic matter by draining excess water from the separator such that trapped dry matter remains. Such a separator is installed where the pipeline has a sudden drop, as perhaps at a junction pit, or far more commonly where the pipeline is discharging to an open water body such as an urban stream.

Here the last length of pipeline can be lowered to provide the necessary fall to provide a dry sump and a separator installed.

By providing a dry sump the quantity of matter to be removed is reduced and thus the ease and efficiency of cleaning and maintenance operations is increased because the need for a water pump to draw the waste from a separator is eliminated. Any dry suction apparatus, such as a street cleaner, may be employed instead.

An advantage of the present invention is to treat the highest proportion of the annual flow as economically as possible so as to provide effective removal of gross pollutants.

The rectangular separator body 1, shown in the Figures, incorporates an upper diversion/bypass chamber 2 that curves down to a separator outlet, an adjacent holding/separation chamber 3 and a lower screened liquid chamber 4. The usually rectangular separator body 1 is preferably formed from reinforced concrete although the other components may be fabricated from materials other than concrete .

Pipeline conduits 5 and 6 are typically already in service although conduit 6 may have to be lowered to provide the fall required between inlet and outlet ports 7 and 8.

As best seen in Figures 4 and 5, screened chamber 4 is located directly below bypass chamber 2 and both abut separation chamber 3 by way of a common wall 22 that extends the height of the separator body 1 from a floor 30 to a ceiling 31. Liquid communication between bypass chamber 2 and separation chamber 3 is provided by a diversion port 9 having an opening 23 in wall 22, and a

port exit 24. Liquid communication between separation chamber 3 and screened chamber 4 is through a bar screen 10 also contained in wall 22, but below diversion port 9, and which filters debris from flows.

An orifice slot 11 is provided in a vertical wall 14 that separates the screened chamber 4 from the bypass chamber 2 and outlet port 8. Orifice slot 11 provides liquid communication between chambers 4 and 2 and controls the flow rate of treated liquid flowing through separation chamber 3 and exiting the separator through the outlet port.

The floor of bypass chamber 2 is raised to form a smooth hump 12 that acts as a diversion weir during moderate flows 13. The hump 12 transitions to vertical wall 14 and terminates at the top edge of the orifice slot 11.

During high flows 17 liquid bypasses separation chamber 3 and screened chamber 4 by flowing over hump 12 and through bypass chamber 2. A gap 15 between the separator body 1 and vertical wall 14 forms a lower part of bypass chamber 2 and is sufficient for the bypass flows to fall to the separator floor 30 before exiting via outlet port 8.

Inspection and maintenance openings 16 are located in ceiling 31 of the separator body 1 and capped by covers 18.

In the first and most common mode of operation shown in the Figures, moderate flow 13 containing floating and entrained solid bodies/ 19 and 20, enters separator body 1 via inlet port 7 and is diverted by hump 12 into adjacent diversion port 9 and then drops into separation chamber 3. The flow 13 then passes into screened chamber 4 through screen 10 that retains floating and solid bodies 19 and 20

in chamber 3. The screened flow 13 exits screened chamber 4 via the orifice slot 11 and the separator body by the outlet port 8.

At higher inflows, the orifice slot 11 throttles flow 13 to separation chamber 3 via the diversion port 9 causing the liquid level 21 in chamber 3 to rise. When the liquid level 33 reaches the top of hump 12 or just below, as shown in Figure 5, the maximum treatable flow rate 13 has been attained.

At this flow rate the screen 10 is fully immersed with the average flow velocity through it regulated by the orifice slot 11 to a non-blocking velocity determined from laboratory tests. This high flow rate is expected to occur only several times a year during heavy rainfall or flash flooding. It is expected that under normal operation liquid will flow through the separator without constriction by the orifice slot. Once drained debris caught in the separation chamber dries and will eventually be removed during cleaning.

The maximum treatable flow through the separator is controlled and can be altered by varying the vertical dimension of the orifice slot 11. Slot 11 extends the full width of vertical wall 14 separating screened chamber 4 from bypass chamber 2. The vertical dimension of the orifice is determined according to the size of the separator and the desired attainable maximum flow by testing and trialling.

A portion 25 of the common wall 22 alongside screen 10 (see Figure 2) acts to keep long objects that may protrude through the screen into screened chamber 4 away from orifice slot 11 and so prevents obstruction of the orifice slot 11. It also acts to prevent long objects that have

passed through screen 10 into screened chamber 4 from snagging near orifice 11 and also assists to align these objects with the flow as it passes through the said orifice.

Wall portion 25 can also act as a baffle for moderate flows distributing the flow as evenly as possible along screen 10 to avoid build up of waste matter at one end of screen 10, which may occur as a result of fast flow through diversion port 9. As shown in Figure 1, diversion port 9 is acutely inclined off bypass chamber 2 to guide flow diverted from hump 12 into separation chamber 3. Flow through diversion port 9 and exiting diversion port exit 24 tends to head towards one end of the separation chamber 3. Portion 25 has the effect of re-distributing any concentration in flow along screen 10.

In the second or bypass mode of operation the total inflow exceeds the maximum treatable flow 13 and so the excess flow 17 passes over the smooth hump 12, down wall 14 and gap 15 to leave the separator together with treated flow 13 via outlet port 8.

At very high excess flows, occurring at super-critical velocity at or near pipe capacity, the hump allows the flow to pass over smoothly without inducing a hydraulic jump that would head upstream with possible local flooding.

A portion of the bypassing super-critical flow is diverted by hump 12 into the diversion port and into the separation chamber. By diverting an amount of the bypassing supercritical flow a positive flow is maintained in the separation chamber which prevents the so-called phenomenon of ^λ scavenging' whereby previously captured matter in the separation chamber is sucked back out of the separation

chamber through the diversion port by the bypassing supercritical flow.

This high excess flow may partially impact on the separator body wall 1, not having sufficient time to fall to the separator floor. However provided the separator body is securely bedded in its excavation, the reactive earth pressures generated can provide adequate resistance to these short-term forces.

Captured matter must be removed from chamber 3 when it is full and the separator checked for blockages or obstructions. Inspection can be carried out from ground level via the inspection/maintenance shafts 16. To pump out captured matter the covers 18 over shafts 16 are removed and the suction hose of the truck-mounted dry vacuum pump lowered into chamber 2.

This operation is simply and quickly conducted as no water is involved and so only blower-type suction air pumps are required. The quantity of matter to be removed is only a fraction of that associated with wet sumps and being dry, can be readily transported for disposal at sanitary landfills .

The frequency of cleaning will depend on the many factors that determine the quantities of matter generated in the upstream catchment and conveyed to the separator. Such factors include local rainfall, drain location and occurrence of storms. However experience suggests that cleaning would generally be once annually.

It will be seen that by applying established hydraulic principles in a novel synergy, a relatively simple yet effective and useful embodiment of the invention has been devised.

Many modifications of this embodiment of the invention will be apparent to those skilled in the art without departing from the spirit and scope of the invention.