IES20110097A2

IES20110097A2 - Improvements in and relating to an effluent treatment assembly

Info

Publication number: IES20110097A2
Application number: IE20110097A
Authority: IE
Inventors: Philip Patrick Peter O'brien
Original assignee: Philip Patrick Peter O'brien
Priority date: 2010-03-02
Filing date: 2011-03-02
Publication date: 2011-10-12
Also published as: WO2011107524A1

Abstract

The present invention concerns an effluent treatment assembly and process for reducing the amount of phosphate in effluent sourced from a primary and/or secondary waste water treatment facility. The effluent treatment assembly comprises phosphate removal filters containing phosphate removing filter media. Each of the phosphate removal filter media comprises a macroporous ion exchange bead which has been impregnated with an ion adsorption material. The advantage of the invention is that both an ion adsorption process and an ion exchange process take place to remove phosphates from effluent in a more efficient manner than has been heretofore known. The phosphate removing filter media is intermittently regenerated using regeneration solution. The effluent treatment process advantageously comprises means for recovering the regeneration solution after use for further re-use. The phosphate removed from the effluent is harvested and may be dehydrated and pelletised to be used as fertiliser pellets.

Description

true copy AS lodged cks re hsbuc ibspkticb iaoEB kbics :? m Bin » Ukl ae.S;i?2fc^. ct :44^1 ΙμΜΜΜ·ΜΜ)ΜΜΜ«ΜΜΙΙΜΙΜ9Η«ΧβΜ>ΜΙ •E 1 1 0097 unci' “Improvements in and relating to an Effluent Treatment Assembly” Introduction This invention relates to an effluent treatment assembly, in particular, the present invention relates to an effluent treatment assembly for carrying out processing on final effluent that has already undergone prior treatment in a waste water treatment plant.

A significant challenge facing local authorities is to ensure that adequate effluent treatment facilities are provided so as to make certain that treated effluent released into the environment does not pose any threat, or at least poses as minimal a threat as possible to the environment. The effluent, which includes but is not limited to raw sewage, factory effluent, processing plant effluent and waste water, must be treated prior to discharge into the environment as surface water.

Typically the effluent will have undergone a number of treatments in primary and secondary waste water treatment plants before being discharged as surface water in the environment. The majority of harmful substances in the effluent will have been removed from the effluent at this stage however not ali contaminants will have been removed. It is desirable to remove as much of the contaminants from the effluent prior to discharge of the effluent into the environment so that said discharge can be carried out in a safe and hygienic manner.

A particular problem with known effluent treatment processes is that the effluent which has been already treated in the primary and secondary waste water treatment plants still contains high levels of contaminants such as phosphates, suspended solids, chemical oxygen demands (CODs) and biological oxygen demands (BODs), all of which are harmful to the environment. In particular, phosphates can be particularly harmful to water systems as they can lead to eutrophication of the water system and this eutrophication encourages the growth of oxygen-depleting plants in the water system which can harm other organisms, such as fish that inhabit the water system. As a result of these environmental concerns, many regulatory bodies including those in Ireland, the United Kingdom, other European countries and the USA, have recently set more stringent limits on the total amount of phosphate which is permitted in effluent discharged as surface water. These limits have been set to IE 1 10097 -2minimise the amount of eutrophication which occurs. Eutrophication is known to take place when phosphate levels in the water system, such as rivers, lakes and the like, rise to above 0.03 mg of phosphate per litre of water. Many primary and secondary waste water treatment plants cannot meet these new low phosphate emission ievels and specific phosphate reducing effluent treatment assemblies are required to work in conjunction with waste water treatment plants to lower the phosphate levels to acceptable levels.

A known type of phosphate removal assembly Is described in the Applicant’s own European Patent Application, EP 09164465, filed on July 2, 2009. In EP 09164465, a tertiary effluent treatment process is applied to effluent received from an effluent source such as primary and secondary waste water treatment plants. The tertiary effluent treatment process is designed to reduce the phosphate levels in the effluent to below the levels which are legally permitted by the various regulatory bodies and associated licences.

The assembly of EP 09164465 comprises a primary filter which is provided to remove suspended solids from the effluent which is received from a preceding waste water treatment plant. The primary filter feeds the filtered effluent to one or more phosphate removal filters which are arranged in series and hold phosphate removal media in columns or filter tanks. The phosphate removal media treats the effluent and reduces the amount of phosphate in the effluent. The phosphate is removed and trapped by the phosphate removal media in the phosphate removal filters. The trapped phosphate builds up until a saturation point is reached whereby the phosphate removal media is no longer effective in removing and trapping phosphate. In order to clean and reactivate the phosphate removal filters for re-use, a regeneration solution comprising a caustic agent is passed through the phosphate removal filters. The regeneration solution dislodges phosphate from the phosphate removal media source regenerating the phosphate removal media to be re-used subsequently. The regeneration solution comprising the removed phosphate is collected in a sedimentation tank. According to the teaching of EP 09164465, the regeneration solution and removed phosphate is allowed to settle over an extended period of time in the sedimentation tank, in this manner, some of the regeneration solution would separate from the removed phosphate such that the separated regeneration solution can be drained off for re-use.

IE 1 1 0 097 -3As disclosed in EP 09164465, once the regeneration solution has removed substantially all of the phosphate from the phosphate removal media in the phosphate removal filters, the pH levels in the phosphate removal filters need to be reduced. Pursuant to the teachings in EP 09164465, the pH levels in the phosphate removal filters is reduced by passing a brine and CO2 mixture through the phosphate removal filters. It is also disclosed that the brine and CO2 mixture may be advantageously made up using treated substantially phosphate-free water from the output of the phosphate removal filters. This treated phosphate-free water is stored in a treated water tank to allow the assembly to pump a portion of this treated water into a mixing tank so as to create the brine and CO2 mixture. Once the pH levels in the phosphate removal filters is reduced to operative levels, the process of removing phosphate by passing the effluent to be treated through the phosphate removal filters can continue.

A number of problems have been found to exist with this known assembly and method as described in EP 09164465.

It was previously understood that the regeneration solution would become separated from the phosphate over time in the sedimentation tank. However, further research has shown that this is not the case, or at least the time required in order to allow the separation take place is quite extensive. The phosphate has a tendency to remain suspended in the regeneration solution and the separation is not as effective as was previously thought. Thus, the regeneration solution cannot be re-used as desired when the invention as described in EP 09164465 is carried out. This results in relatively high operating costs for the effluent treatment assembly as the quantity of regeneration solution which is recovered for re-use is not as large as had previously been hoped for, and larger amounts of regeneration solution are required in order to operate the effluent treatment assembly. This is understandably undesirable for iocat authorities and councils who would most likely have to facilitate the higher operating costs for the effluent treatment assembly.

Moreover, the operating costs of the known system in EP 09164465 are also considered to be relatively high as the phosphate removal filters require a brine and CO2 mixture to be formed to wash through the filters so as to reduce their pH levels.

IE 1 1 0 097 -4This requires provision of a treated water tank and a discharge tank to allow a portion of the treated water to be pumped into a mixing tank within the effluent treatment assembly to form the brine and CO2 mixture.

European Patent Publication Number EP 1 900 691 A1 (Asahi Kasei Chemical Corporation) discloses an effluent treatment process which goes some way to overcoming some of the above mentioned problems. The effluent treatment process of EP 1 900 691 uses fibril-based porous formed adsorption articles, the articles having a structure formed from a fibril carrying an ion adsorbing coating of iron oxide, as the phosphate removal media in the phosphate removal filters.

The fibril-based porous formed adsorption articles are used to adsorb ions from water to be treated, including fluorine ions, borate ions, phosphate ions, chlorine ions and other types of contaminate ions. The porous formed articles are packed into a column or adsorption tower forming the phosphate removal filter and effluent to be treated is passed through the phosphate removal filter, contacting the effluent to be treated with the porous formed article sufficiently so as to effect a high contact efficiency.

According to European Patent Publication Number EP 1 900 691, the porous formed article must be constructed from a fibril. The fibril is made of an organic polymer resin and the fibril is a fibrous structure which has internal cavities forming communicating pores within the fibril itself whereby the opening of these communicating porous is on the surface of the fibril. The fibril is arranged to form a three-dimensional article which is highly porous as the three-dimensional article is formed to comprise a number of through channels which in conjunction with the communicating pores of the fibril itself result in a large surface area on the fibril-based porous formed article.

The large surface area on the fibril-based porous formed article supports an inorganic ion adsorbing material which adsorbs ions from the effluent to be treated. Therefore, the contaminate ions are adsorbed by the inorganic material using an ion adsorption process. In order to allow the adsorption process to take place effectively, pH levels of the effluent which is supplied to the ion adsorption filters (phosphate removal filters) must be closely monitored and maintained to be within an acceptable range, which is described as a pH of approximately 3. The requirement for the IE 110097 -5effluent entering the effluent treatment process of EP 1 900 691 to have a relatively pH is a cumbersome requirement of the effluent treatment process of EP 1 900 691 and it is desirable that this requirement be obviated. This is particularly true as the vast majority of primary and secondary waste water treatment plants expel effluent which will generally, under regulatory licence and/or local council control, have a pH in the range of 6 to 9. Therefore, the effluent treatment process of EP 1 900 691 requires this pre-treatment pH adjustment step which is costly to install as part of the assembly and also costly and time consuming to run continually as part of the effluent treatment process.

As previously described, the inorganic ion adsorbing material which acts as the phosphate removing material on the phosphate removal media has a saturation point beyond which the efficiency of the inorganic ion adsorbing material is lessened. The inorganic ion adsorbing material needs to be regenerated as described in EP 09164465. EP 1 900 691 describes passing regeneration solution through the phosphate removal filters to regenerate the inorganic ion adsorbing material on the fibril-based porous formed articles which are the phosphate removal media in EP 1 900 691. Again, the regeneration solution is passed through the phosphate removal filters and is subsequently collected in a tank. In order to assist with the precipitation of the phosphate within the phosphate-enriched regeneration solution, a precipitating agent (sedimentation agent) in the form of a hydroxide, preferably calcium hydroxide according to EP 1 900 691 is added to assist with the precipitation of phosphate within the phosphate-enriched regeneration solution. Thus, the desorbed ions, which for the purposes of this discussion are assumed to be phosphate ions, may be easily removed and recovered.

Furthermore, as described with reference to EP 09164465, the pH levels in the phosphate removal filters need to be adjusted after the regeneration solution has been passed through. The pH levels in the phosphate removal filters are returned and stabilised to an operable level by passing a pH neutralising solution through the phosphate removal fitters.

The effluent treatment assembly in EP 1 900 691 describes an ion adsorbing process which is carried out using a fibril-based porous ion adsorption article. The assembly removes phosphate from the effluent, however, an improvement in the operating IE 1 1 ο θ 9 ζ -6costs and efficiency of the process is desirable. In particular, the effect of the ion adsorption process on the pH levels in the phosphate removal filters requires a relatively high degree of monitoring and maintenance. A pH-adjusting agent is required to maintain the pH level of the effluent to be treated in the phosphate removal filters to be within an acceptable range. This pH-level monitoring and maintenance is costly and time-consuming to carry out and adds to the overall operating costs of the assembly.

Moreover, the assembly described in EP 1 900 691 is also disadvantageous as the fibril-based porous formed article, whilst having a certain advantages as described in EP 1 900 691, is relatively complicated to construct. Thus, the use of the fibril results in a relatively expensive filter media which is costly to produce. This increases the overall operating cost of the phosphate removal assembly described in EP 1 900 691.

It is an object of the present invention to provide an effluent treatment process and assembly for carrying out the treatment of final effluent that overcomes at least some of the problems with the afore-mentioned known processes. In particular, it is an object of the present invention to provide an effluent treatment process and assembly for carrying out a process that removes high levels of phosphate from the effluent in an efficient and operational cost effective manner.

Statements of Invention The present invention is directed towards an effluent treatment assembly for treating effluent by reducing phosphate content in the effluent, the assembly comprising a primary inlet filter for filtering effluent received from an effluent source, one or more phosphate removal filters to treat the filtered effluent and a discharge outlet for discharging treated effluent into an environment, wherein, the one or more phosphate removal filters each comprise phosphate removing filter media, the phosphate removing filter media comprising a plurality of macroporous ion exchange beads which have been each impregnated with an ion adsorption material.

The advantage of using a macroporous ion exchange bead material is that the bead itself removes phosphate from the effluent in addition to the typical ion adsorption process which will be effected by the ion adsorption material which is impregnated on JE 1 1 Ο ο 9 7 -7each bead. Therefore there is a double effect of ion exchange and ion adsorption which is more effective at removing phosphate from effluent over known effluent treatment process from the prior art. According to the present invention a contact time of between 1 and 3 minutes, and preferably 2 minutes is all that is required between the phosphate rich effluent and the phosphate removing filter media in order for effective ion exchange and ion adsorption to take place so as to reduce the levels ot phosphates in the effluent to acceptable levels. This contact time is far lower than contact times needed in known systems and therefore the effluent treatment assembly of the present invention is more economic to operate and will operate at faster rates than known effluent treatment systems.

In a further embodiment, the ion adsorption material is iron oxide (FeO).

In a further embodiment, the effluent treatment assembly further comprises a regeneration solution tank which is connected to the one or more phosphate removal filters to provide a regeneration solution which is passed through the one or more phosphate removal filters; and, the regeneration solution comprises less than 20% caustic agent by volume.

In a further embodiment, the effluent treatment assembly further comprises a regeneration solution tank which is connected to the one or more phosphate removal filters to provide a regeneration solution which is passed through the one or more phosphate removal filters; and, the regeneration solution comprises 0.5% to 5% caustic agent by volume.

In a further embodiment, the effluent treatment assembly further comprises a regeneration solution tank which is connected to the one or more phosphate removal filters to provide a regeneration solution which is passed through the one or more phosphate removal filters; the regeneration solution comprises 2% to 3.5% caustic agent by volume. This range of 2% to 3.5% caustic agent by volume in the regeneration solution has been found to be particularly optimal.

In a further embodiment, the ratio of regeneration solution passed through the one or more phosphate removal filters to phosphate removing filter media is in the range of 5:1 to 5.5:1.

IE 1 1 ο ο 9 7 -8Ιη a further embodiment, the ratio of regeneration solution passed through the one or more phosphate removal filters to phosphate removing filter media is in the range of 7:1 to 8:1. This range of ratio of regeneration solution passed through the one or more phosphate removal filters to phosphate removing filter media has been found to be particularly optimal.

In a further embodiment, the caustic agent is Sodium Hydroxide (NaOH).

In a further embodiment, the effluent treatment assembly further comprises a caustic agent measurement device to measure the level of caustic agent in the regeneration solution in the regeneration solution tank to determine if fresh caustic agent is required, and, the regeneration solution tank is connected to a fresh caustic agent source to allow the regeneration solution in the regeneration solution tank to be topped up with fresh caustic agent as required. In a preferred embodiment, fresh caustic agent may be added to the regeneration solution in the regeneration solution tank, instead of adding fresh regeneration solution. In one embodiment, treated water from the effluent treatment process is firstly directed into the regeneration solution tank to bring the volume of fluid in the regeneration solution tank up to a predetermined level and then caustic agent is added to the regeneration solution tank until a desired alkalinity condition is met. in this manner, fresh caustic agent, rather than pre-mixed fresh regeneration solution, is added to the regeneration solution tank as required. This reduces the requirement to have a further pre-mixed regeneration solution storage tank for providing pre-mixed regeneration solution to top up the regeneration solution tank.

This reduces the cost of the effluent treatment assembly.

In a further embodiment, the effluent treatment assembly further comprises a caustic agent measurement device to measure the level of caustic agent in the regeneration solution in the regeneration solution tank to determine if fresh regeneration solution is required, and, the regeneration solution tank is connected to a fresh regeneration solution source to allow the regeneration solution in the regeneration solution tank to be topped up with fresh regeneration solution as required.

In a further embodiment, the caustic agent measurement device is a toroidal conductivity monitor.

IE 1 1 Ο Ο 9 7 -9Ιη a further embodiment, the assembly further oomprises a sedimentation tank which is connected to the one or more phosphate removal filters to receive a phosphateenriched regeneration solution which has passed through the one or more phosphate removal filters and has removed phosphate from the phosphate removing filter media; and, a calcium chloride storage tank which is fluidly connected to the sedimentation tank to allow Calcium Chloride (CaCI2) to be added to the phosphate-enriched regeneration solution so as to form a sedimentation mixture in the sedimentation tank; wherein, the sedimentation tank comprises an upper outlet to allow recovered regeneration solution which has separated from the sedimentation mixture to be bled off and passed into the regeneration solution tank for re-use in the effluent treatment assembly, and, a lower outlet for releasing a sedimentation sludge.

The advantage of using Calcium Chloride (CaCI2) over known precipitating agents in the prior art is that the CaCI2 causes a chemical reaction to occur in the sedimentation tank and a sedimentation sludge, which will typically be Hydroxyapatite, namely Ca5(PO4)3OH, is formed and the phosphate which was removed from the phosphate removal filters by the regeneration solution is removed from the regeneration solution. Hence, the regeneration solution may be reused in the effluent treatment process. This is cost-effective as the regeneration solution does not need to be newly formed on each occasion that the media in the filters are to be regenerated. In particular, the use of a CaCI2 in the sedimentation tank has been found to cany out the sedimentation and separation in a relatively fast manner in comparison to prior art assemblies. This is advantageous as the entire effluent treatment process can thus be sped up.

In a further embodiment, the sedimentation sludge is dehydrated and pelletised. This is advantageous as the harvested phosphate may be used commercially and sold as fertiliser for example.

In a further embodiment, the assembly further comprises a connection between the sedimentation tank and the regeneration solution tank to allow regeneration solution which has been recovered from the sedimentation tank to be returned to the regeneration solution tank, and, a monitoring unit in the regeneration solution tank to monitor the effective quality of the regeneration solution in the regeneration solution IE 1 1 Ο 097 -10tank and determine if fresh caustic agent and/or fresh regeneration solution needs to be added to the regeneration solution tank.

In a further embodiment, the one or more phosphate removal filters comprise separated media retaining column compartments which are fluidly connected in series.

By providing the one or more phosphate removal filters with separated media retaining column compartments which are fluidly connected in series, the separated media retaining column compartments behave as if they are separated filter columns and therefore an advantage can be gained by passing the regeneration solution through each of the separated media retaining column compartments in turn, as described in greater detail further below.

In a further embodiment, the separated media retaining column compartments are fluidly connected by internal piping which passes effluent through divider walls creating the separated media retaining column compartments.

In a further embodiment, the separated media retaining column compartments are fluidly connected by external piping which passes effluent through divider walls creating the separated media retaining column compartments.

In a further embodiment, the effluent treatment assembly further comprises a carbon dioxide storage tank which is connected to the one or more phosphate removal filters to allow carbon dioxide (CO2) to be passed through the one or more phosphate removal filters to reduce the pH levels in the one or more phosphate removal filters after the regeneration solution has been passed through the one or more phosphate removal filters.

This is advantageous over the known method as only CO2 is used to reduce the pH level in the one or more phosphate removal filters. Brine is not required and therefore the cost of regenerating tiie filters is reduced. The CO2 may be stored in a CO2 storage tank and may be injected into water and stored in a tank prior to being passed through the one or more phosphate removal filters.

The CO2 may be injected into water and stored in a CO2 water mixture tank prior to IE11 Ο Ο 9 7 -11 being passed through the one or more phosphate removal filters to reduce the pH levels in the one or more phosphate removal filters. Alternatively, in a preferred embodiment, the CO2 is injected into a backwash water stream and is passed directly through the one or more phosphate removal filters without being stored in any CO2 water mixture tank, in a further embodiment, the CO2 is injected directly into a stream of water and passed directly through the one or more phosphate removal filters without storage of the CO2 water mixture in any CO2 water mixture tank prior to passing through the one or more phosphate removal filters. The contact time required for pH neutralisation using a CO2 only agent has been found to be in the range of 2 to 4 minutes and preferably 3 minutes.

Alternatively, as mentioned above, to reduce assembly infrastructure and costs, the CO2 may be injected directly into a backwash pipe and passed immediately through the one or more phosphate removal filters to reduce the pH levei in the phosphate removal filters. As only CO2 is used in this pH neutralisation step, the pH levels in the one or more phosphate removal filters will be reduced in less amount of time when compared to having to pass a brine solution injected with CO2 through the one or more phosphate removal filters. The contact time required for pH neutralisation using a CO2 only agent has been found to be in the range of 2 to 4 minutes and preferably 3 minutes. in a further embodiment, the assembly further comprises a treated water tank tor receiving and storing treated effluent from the one or more phosphate removal filters for use as treated water in the effluent treatment process, and, discharging the remainder of the treated water from the one or more phosphate removal filters directly into the environment.

In a further embodiment, untreated effluent may be advantageously by-passed, using a side stream, to the outlet of the phosphate removal filters for mixing with the treated effluent from the phosphate removal filters to produce a mixed treated and untreated effluent output which is just within the limit of regulatory conditions tor the amount of phosphate which may be in a water system. Thus, only the minimum amount of effluent is treated to produce a treated effluent mixture which is within regulatory requirements.

In a further embodiment, the assembly further comprises an actuated valve directing treated effluent away from the discharge outlet and back into the effluent treatment IE 1 1 0 0 9 7 -12assembly for use as treated water in the effluent treatment assembly. This is advantageous as it removes the need for a treated water tank.

In a further embodiment, an ultraviolet (UV) light is provided in the assembly to irradiate any bacteria in the treated water which is to be used in the effluent treatment assembly.

This is advantageous as only the treated effluent which is to be used as treated water in the effluent treatment assembly will be irradiated by the UV light. This wiil lower the operating cost in comparison to the existing processes where all of the treated effluent may have been used as treated water in the effluent treatment assembly, thus necessitating more irradiation to be used. Alternatively, the UV light may be located at the iniet of the effluent treatment assembly prior to the primary filter, or alternatively the UV light may be installed between the primary filter and the one or more phosphate removal filters. In a further embodiment, an ultraviolet (UV) light is provided in the assembly to irradiate bacteria in all of the effluent entering the effluent treatment assembly. This is advantageous as all of the effluent entering the effluent treated assembly will have been irradiated.

The present invention is further directed towards an effluent treatment process for treating effluent by reducing phosphate content in the effluent, the process comprising the steps of filtering effluent received from an effluent source using a primary inlet filter; treating the filtered effluent using one or more phosphate removal filters; and, discharging the treated effluent into an environment through a discharge outlet, wherein, the process further comprises the step of treating the filtered effluent using phosphate removing filter media, the phosphate removing filter media comprising a plurality of macroporous ion exchange beads which have been each impregnated with an ion adsorption material.

The advantage of using a macroporous ion exchange bead material is that the bead itself removes phosphate from the effluent in addition to the typical ion adsorption process which will be effected by the ion adsorption material which is impregnated on each bead. Therefore there is a double effect of ion exchange and ion adsorption which is more effective at removing phosphate from effluent over known effluent treatment process from the prior art. According to the present invention a contact time of between 1 and 3 minutes, and preferably 2 minutes is all that is required between the phosphate It 1 1 0 0 9 7 -13rich effluent and the phosphate removing filter media in order for effective ion exchange and ion adsorption to take place. This contact time is far lower than contact times needed in known systems and therefore the effluent treatment process of the present invention is more economic to operate and will operate at faster rates than known effluent treatment systems.

In a further embodiment, the ion adsorption material is iron oxide (FeO).

In a further embodiment, the effluent treatment process further comprises the step of intermittently regenerating the one or more phosphate removal filters using a regeneration solution which is passed through the one or more phosphate removal filters; whereby, the regeneration solution comprises less than 20% caustic agent by volume.

In a further embodiment, the effluent treatment process further comprises the step of intermittently regenerating the one or more phosphate removal filters using a regeneration solution which is passed through the one or more phosphate removal filters; whereby, the regeneration solution comprises 0.5% to 5% caustic agent by volume.

In a further embodiment, the effluent treatment process further comprises the step of intermittently regenerating the one or more phosphate removal filters using a regeneration solution which is passed through the one or more phosphate removal filters; whereby, the regeneration solution comprises 2% to 3.5% caustic agent by volume. This range of 2% to 3.5% caustic agent by volume in the regeneration solution has been found to be particularly optimal. in a further embodiment, the ratio of regeneration solution passed through the one or more phosphate removal filters to phosphate removing filter media is in the range of 5:1 to 5.5:1.

In a further embodiment, the ratio of regeneration solution passed through the one or more phosphate removal filters to phosphate removing filter media is in the range of 7:1 to 8:1. This range of ratio of regeneration solution passed through the one or more phosphate removal filters to phosphate removing filter media has been found to be IE 1 1 0 0 9 7 -14particularly optimal.

In a further embodiment, the caustic agent is Sodium Hydroxide (NaOH).

Ina further embodiment, the effluent treatment process further comprises the steps of measuring level of caustic agent in the regeneration solution in the regeneration solution tank to determine if fresh caustic agent is required; and, topping up the regeneration solution in the regeneration solution tank with fresh caustic agent as required. In a preferred embodiment, fresh caustic agent may be added to the regeneration solution in the regeneration solution tank, instead of adding fresh regeneration solution. Treated water from the effluent treatment process is firstly directed into the regeneration solution tank to bring the level of fluid in the regeneration solution tank up to a predetermined level and then caustic agent is added to the regeneration solution tank until a desired mixture condition is met. In this manner, fresh caustic agent, rather than pre-mixed fresh regeneration solution, is added to the regeneration solution tank as required. This reduces the requirement to have a further pre-mixed regeneration solution storage tank for providing pre-mixed regeneration solution to top up the regeneration solution tank. This reduces the cost of the effluent treatment assembly.

Ina further embodiment, the effluent treatment process further comprises the steps of measuring level of caustic agent in the regeneration solution in the regeneration solution tank to determine if fresh caustic agent is required; and, topping up the regeneration solution in the regeneration solution tank with fresh regeneration solution as required.

In a further embodiment, the process further comprises the steps of receiving a phosphate-enriched regeneration solution which has passed through the one or more phosphate removal filters and has removed phosphate from the phosphate removing filter media; adding Calcium Chloride (CaCI2) to the phosphate-enriched regeneration solution so as to form a sedimentation mixture in a sedimentation tank; and, allowing the sedimentation mixture to settle and separate in the sedimentation tank such that recovered regeneration solution settles atop a sedimentation sludge; passing the recovered regeneration solution which has separated from the sedimentation sludge IE 1 1 0 0 9 7 - 15into the regeneration solution tank for re-use in the effluent treatment assembly; and, removing the sedimentation sludge from the sedimentation tank.

The advantage of using Calcium Chloride (CaCI2) over known precipitating agents in the prior art is that the CaCI2 causes a chemical reaction to occur in the sedimentation tank and a sedimentation sludge, which will typically be Hydroxyapatite, namely Ca5(PO4)3OH, is formed and the phosphate which was removed from the phosphate removal filters by the regeneration solution is removed from the regeneration solution. Hence, the regeneration solution may be reused in the effluent treatment process. This is cost-effective as the regeneration solution does not need to be newly formed on each occasion that the media in the filters are to be regenerated. In particular, the use of a CaCI2 in the sedimentation tank has been found to carry out the sedimentation and separation in a relatively fast manner in comparison to prior art assemblies. This is advantageous as the entire effluent treatment process can thus be sped up.

In a further embodiment, the removed sedimentation sludge is dehydrated and pelletised for use as a fertiliser. This is advantageous as commercial use can be made of the harvested phosphate.

By providing the one or more phosphate removal filters with separated media retaining column compartments which are fluidly connected in series, the separated media retaining column compartments behave as if they are separated filter columns and therefore an advantage can be gained by passing the regeneration solution through each of the separated media retaining column compartments in turn.

In a further embodiment, the separated media retaining column compartments are fluidly connected by external piping which passes effluent through divider walls creating IE 1 1 0 097 - 16the separated media retaining column compartments. in a further embodiment, the effluent treatment process further comprises the step of passing carbon dioxide (CO2) through the one or more phosphate removal filters to reduce the pH levels in the one or more phosphate removed filters after the step of passing the regeneration solution through the one or more phosphate removal filters has been effected.

This is advantageous over the known method as only CO2 is used to reduce the pH level in the one or more phosphate removal filters. Brine is not required and therefore the cost of regenerating the filters is reduced. The CCb may be stored in a CO2 storage tank and may be injected into water and stored in a tank prior to being passed through the one or more phosphate removal filters. The contact time required for pH neutralisation using a CO2 only agent has been found to be in the range of 2 to 4 minutes and preferably 3 minutes.

The CO2 may be injected into water and stored in a CO2 water mixture tank prior to being passed through the passed through the one or more phosphate removal filters to reduce the pH levels in the one or more phosphate removal filters. Aiternatively, in a preferred embodiment, the CO2 is injected into a backwash water stream and is passed directly through the one or more phosphate removal filters without being stored in any CO2 water mixture tank. In a further embodiment, the step of passing the CO2 through the one or more phosphate removal filters oomprises injection the CO2 directly into a stream of water and passing the CO2 enriched water stream directly through the one or more phosphate removal filters without storing the CO2 enriched water in a tank prior to passing it through the one or more phosphate removal fitters.

Alternatively, to reduce assembly infrastructure and costs, the CO2 may be injected directly into a backwash pipe and passed immediately through the one or more phosphate removal filters to reduce the pH level in the phosphate removal filters. As only CO2 is used in this pH neutralisation step, the pH levels in the one or more phosphate removal filters will be reduced in less amount of time when compared to having to pass a brine solution injected with 002 through the one or more phosphate removal filters. The contact time required for pH neutralisation using a CO2 only agent has been found to be in the range of 2 to 4 minutes and preferably 3 minutes.

IE 11 0 0 9 7 -17ln a further embodiment, the process further comprises the steps of receiving and storing treated effluent from the one or more phosphate removal filters for use as treated water In the effluent treatment process; and, discharging the remainder of the treated water from the one or more phosphate removal filters directly into the environment.

In a further embodiment, the process further comprises the step of actuating a valve to direct treated effluent away from the discharge outlet and back into the effluent treatment assembly for use as treated water in the effluent treatment assembly. This is advantageous as it removes the need for a treated water tank.

In a further embodiment, the process further comprises the step of irradiating any bacteria in the treated water which is to be used in the effluent treatment assembly with an ultraviolet (UV) light.

This is advantageous as only the treated effluent which is to be used as treated water in the effluent treatment assembly will be irradiated by the UV light. This will lower the operating cost in comparison to the existing process where all of the treated effluent may have been used as treated water in the effluent treatment assembly, thus necessitating more irradiation to be used. Alternatively, the UV light may be located at the inlet of the effluent treatment assembly prior to the primary filter, or alternatively the UV light may be installed between the primary fitter and the one or more phosphate removal filters. In a further embodiment, the process further comprises the step of irradiating any bacteria in the effluent entering the effluent treatment assembly with an ultraviolet (UV) light. This is advantageous as all of the effluent entering the effluent treatment process wiil have been irradiated.

According to the invention there is provided an effluent treatment process comprising the steps of filtering effluent received from a waste water treatment plant with a primary inlet filter; passing the filtered effluent through one or more phosphate removal filters to treat the filtered effluent; discharging the treated effluent into the environment; passing regeneration solution intermittently through the phosphate removal filters to take phosphate out of the phosphate removal filters; collecting the regeneration solution and the phosphate in a sedimentation tank; wherein the method further comprises adding a IE 110097 - 18calcium-based substance to the sedimentation tank to create a sedimentation mixture; allowing the sedimentation mixture to settle in the sedimentation tank so as to leave the regeneration solution, substantially devoid of phosphate, and a sedimentation sludge comprising the phosphate and the calcium-based substance; recovering the regeneration solution for re-use in the effluent treatment process; and releasing the sedimentation sludge from the sedimentation tank.

The present invention is advantageous over the known prior art as the present invention uses a calcium-based substance to carry out the sedimentation process in the sedimentation tank. The caicium-based substance causes a chemical reaction to occur in the sedimentation tank and a sedimentation sludge, which will typically be Hydroxyapatite, namely Ca6(PO4)3OH, is formed and the phosphate which was removed from the phosphate removal filters by the regeneration solution is removed from the regeneration solution. Hence, the regeneration solution may be reused in the effluent treatment process. This is cost-effective as the regeneration solution does not need to be newly formed on each occasion that the media in the filters are to be regenerated.

The use of a calcium-based substance in the sedimentation tank also causes the sedimentation of the phosphate to be carried out in a relatively fast manner. This is advantageous as the entire effluent treatment process can be sped up.

In a further embodiment, the process further comprises the step of passing carbon dioxide (CO2) through the phosphate removal filters to reduce the pH levels in the filters, after the regeneration solution has been passed through the filters.

This is advantageous over the known method as only CO2 is used to reduce the pH level in the one or more phosphate removal filters. Brine is not required and therefore the cost of regenerating the filters is reduced. The CO2 may be stored in a CO2 storage tank and may be injected into water and stored in a tank prior to being passed through the one or more phosphate removal filters. Alternatively, to reduce assembly infrastructure and costs, the CO2 may be injected directly into a backwash pipe and passed immediately through the one or more phosphate removal filters to reduce the pH level in the phosphate removal filters. As only CO2 is used in this pH neutralisation step, the pH levels in the one or more phosphate removal filters will be reduced in less IE 11 ο ο 9 7 amount of time when compared to having to pass a brine solution injected with CO2 through the one or more phosphate removal filters.

In a further embodiment, the process further comprises the steps of passing the regeneration solution from the sedimentation tank to a regeneration solution tank; storing the regeneration solution in the regeneration solution tank, ready to be passed intermittently through the phosphate removal filters; and, topping up the regeneration solution in the regeneration solution tank with fresh caustic agent and water and/or fresh regeneration solution as required.

In a further embodiment, the process further comprises the step of measuring the level of caustic agent in the regeneration solution in the regeneration solution tank to determine if fresh caustic agent and/or fresh regeneration solution is required. In a preferred embodiment, fresh caustic agent may be added to the regeneration solution in the regeneration solution tank, instead of adding fresh regeneration solution. Treated water from the effluent treatment process is directed into the regeneration solution tank to bring the level of fluid in the regeneration solution tank up to a predetermined level and caustic agent is then added to the regeneration solution tank until a desired mixture condition is met. In this manner, fresh caustic agent, rather than pre-mixed fresh regeneration solution, is added to the regeneration solution tank as required. A toroidal conductivity monitor may be advantageously used to measure the level of caustic agent in the regeneration solution.

In a further embodiment, the process further comprises the step of supplying some of the treated water from the filters to a treated water tank for use as treated water in the effluent treatment process, and, discharging the remainder of the treated water from the filters into the environment. In yet a further embodiment, treated water is directed to parts of the effluent treatment assembly, such as the regeneration solution tank or a phosphate removal filter backwash piping system, directly from the discharge outlet pipe without being stored in a treated water tank first.

In a further embodiment, the calcium-based substance is Calcium Chloride (CaCI2).

In a further embodiment, the regeneration solution comprises a caustic agent. In a further embodiment, the caustic agent is caustic soda. In a further embodiment, the IE 1 1 ο ο 9 7 -20percentage of caustic soda in the regeneration solution is maintained to be lower than 20%, and preferably in the range of 0.5% to 5%.

The present invention is further directed towards an effluent treatment assembly comprising an inlet to receive effluent from a waste water plant, a plurality of phosphate removal fitters arranged to treat the received effluent and a discharge outlet to discharge the treated effluent into the environment; whereby, the effluent treatment assembly further comprises a regeneration solution tank which is connected to the plurality of filters to allow a regeneration solution to be passed through the plurality of filters, a sedimentation tank which is connected to the plurality of phosphate removal filters to receive the regeneration solution passed through the filters and phosphate removed from the filters by the regeneration solution, and, a calcium-based substance storage tank which is connected to the sedimentation tank to allow a calcium-based substance to be added to the regeneration solution and the phosphate to form a sedimentation mixture in the sedimentation tank; wherein, the sedimentation tank comprises an upper outlet to allow regeneration solution which has separated from the sedimentation mixture to be passed into the regeneration solution tank for re-use in the effluent treatment assembly, and, a lower outlet for releasing a sedimentation sludge.

In a further embodiment, the effluent treatment assembly further comprises a carbon dioxide storage tank which is connected to the phosphate removal filters to allow carbon dioxide to be passed through the filters to reduce the pH levels in the filters after the regeneration solution has been passed through the filters.

In a further embodiment, the effluent treatment assembly further comprises a regeneration solution tank to store the regeneration solution for use in the effluent treatment assembly and a fresh regeneration solution source connected to the regeneration solution tank to aliow the regeneration solution in the regeneration solution tank to be topped up with fresh regeneration solution as required. in a further embodiment, the effluent treatment assembly further comprises a caustic agent measurement device to measure the level of caustic agent in the regeneration solution in the regeneration solution tank to determine if fresh regeneration solution is required. In a further embodiment, the caustic agent measurement device is a toroidal conductivity monitor.

IE 1 1 0 0 97 -21 In a further embodiment, the effluent treatment assembly further comprises a treated water tank to receive some of the treated effluent from the filters for use as treated water in the effluent treatment assembly. In a preferred embodiment, an ultraviolet (UV) light is provided to irradiate any bacteria in the treated water which is to be used in the effluent treatment assembly. This is advantageous as only the treated effluent which is to be used as treated water in the effluent treatment assembly will be irradiated by the UV light. This will lower the operating cost in comparison to the existing process where all of the treated effluent may have been used as treated water in the effluent treatment assembly, thus necessitating more irradiation to be used.

The present invention is further directed towards a method of regenerating media in a phosphate removal filter by passing a regeneration solution over the media to remove phosphate from the media and subsequently passing carbon dioxide over the media to reduce the pH levei of the media in the filter.

The present invention is further directed towards a method for recovering regeneration solution for re-use in an effluent treatment assembly comprising the steps of passing the regeneration solution through one or more filters in the effluent treatment assembly to remove phosphate from the filters; passing the regeneration solution comprising the phosphate to a sedimentation tank; adding a calcium-based substance to the regeneration solution and the phosphate in the sedimentation tank; allowing the regeneration solution to become separated from the phosphate and the calcium-based substance in the sedimentation tank; and, bleeding off the regeneration solution from the sedimentation tank to allow the regeneration solution to be re-used in the effluent treatment assembly.

Detailed Description of the Invention The invention will now be more clearly understood from the following description of some embodiments thereof given by way of example only, in which: Figure 1 is a diagrammatic representation of an effluent treatment assembly in accordance with the present invention; IE 11 ο ο 9 7 -22Figure 2 is a table showing the percentage of phosphate removed from a media retaining column compartment in a phosphate removal filter for different passes of regeneration solution through the effluent treatment assembly in accordance with the present invention; and, Figure 3 is a diagrammatic representation of a pair of phosphate removal filters for use in an effluent treatment assembly in accordance with the present invention, wherein each of the phosphate removal filters has been divided into separated media retaining column compartments.

Referring to Figure 1, there is provided an effluent treatment assembly indicated generally by the reference numeral 100.

A waste water treatment plant 102 delivers partially treated effluent to a sump 104. It will be readily appreciated that the effluent source is commonly a primary or secondary waste water treatment plant, however the effluent source could also be factory effluent, processing plant effluent and/or residential waste water effluent which may not necessarily have been treated in a primary or secondary waste water treatment plant.

The partially treated effluent is delivered by a pump 106, or gravity in an alternative embodiment, at a pre-determined rate, from the sump 104 through a conduit 108 into the effluent treatment assembly 100, to a primary filter 110. The partially treated effluent, which will be interchangeable used with the term effluent throughout this specification, may be preferably analysed using a determining means 112 to determine flow rate, pH level, turbidity and/or phosphate content of the effluent whilst the effluent is delivered towards the primary filter 110.

The primary filter 110 is preferably a glass media filter however it will be understood that any suspended solid (SS) filter may be used such as a sand filter or a micro screen drum filter. The pore size of the SS primary filter 110 should be preferably less than 10 micron. The determining means 112 may alternatively be installed directly subsequent to the primary filter 110, within the effluent treatment assembly 100. If the effluent does not meet required criteria, such as the effluent comprising suspended solids which are too large and/or too plentiful, or the pH of the effluent II 1 1 0 097 -23being outside an operable range which is generally 6 to 9 pH, then control valves (not shown) will divert the effluent back from the effluent treatment assembly 100 to the waste water treatment plant 102 or to by-pass the one or more phosphate removal filters and discharge the untreated effluent along with the treated affluent into a water system. The untreated effluent would only be allowed to by-pass the effluent treatment assembly 100 if the treated effluent contains phosphate of sufficiently low levels such that the combination of the treated effluent and untreated effluent results in discharged effluent which does not increase the level of phosphate in the water system above regulatory permitted thresholds. In a further embodiment, a user (not shown) may set the levels of the above mentioned criteria for acceptance or rejection of effluent into the effluent treatment assembly 100 using a controller unit 188.

The effluent is passed through the primary filter 110 to a series of three phosphate removal filters 114,116, 118 via conduits 113,120 and 122. The phosphate removal filters 114, 116, 118 treat the effluent by reducing the amount of phosphate in the effluent. In a preferred embodiment, the phosphate removal filters 114, 116, 118 each comprise phosphate removal media of polymer based beads impregnated with iron oxide nano-particles. In a preferred embodiment, the phosphate removal media is in the form of a macroporous ion exchanging resin impregnated with the iron oxide (FeO) nano-particles. Macroporous materials are generally understood to have average pore diameters which are greater than 50 nm. Therefore, the phosphate removal media removes phosphate ions from the effluent through both an ion exchange process and through an ion adsorption process which has been found to be more operational efficient and cost effective than the ion adsorption only processes which are known from the prior art. The preferred contact time between the effluent to be treated and the phosphate removal media in the phosphate removal filters 114,116,118 is between 1 and 3 minutes and is optimally 2 minutes.

After a period of use, the phosphate removal media will become saturated with phosphate ions and the effectiveness of the phosphate removal media is lessened. In order to allow for a cost effective effluent treatment assembly 100, the phosphate removal media is regenerated for re-use by passing regeneration solution through the phosphate removal filters 114, 116,118. This process will be described in greater detail below.

IE 110 097 -24The effluent is finally passed out of the phosphate removal filters 114,116,118 along a conduit 124 towards a discharge outlet 128. The treated effluent, or treated water at this stage, is discharged as surface water into the environment through the discharge outlet 128. A discharge monitoring unit 126 monitors the phosphate level, pH level and/or bacterial content of the treated effluent which is being discharged as surface water. It will be understood that such a discharge monitoring unit 126 may not form part of the assembly. In one embodiment, should the treated effluent not meet certain criteria, such as appropriately low levels of phosphate, the effluent may be redirected away from the discharge outlet 128 and passed through the effluent treatment assembly 100 for further treatment via a return conduit (not shown).

Although three phosphate removal filters 114, 116, 118 are shown in Figure 1, any number of filters may be used. The use of three filters allows for one or more of the filters to be backwashed or regenerated whilst the remaining filter, or filters, continue to operate as normal as the filters 114,116, 118 are shown to be arranged in parallel. This could allow the effluent treatment assembiy 100 to operate continuously without having to stop for maintenance to be carried out.

A portion of the treated effluent is supplied to a treated water tank 134 via a conduit 130. An ultraviolet (UV) light 132 is provided along the conduit 130 to irradiate any bacteria in the treated effluent which is being supplied to the treated water tank 134. It will be understood that the provision of the UV light 132 is not an essential feature of the invention, and in a further embodiment, the conduit 130 may not be provided with any UV light 132. In yet a further embodiment, alternative bacteria depleting means such as an ozone injector may be used, it will be understood that the UV light 132 may be installed at any point in the effluent treatment assembly, for example before the primary inlet filter 110 or between the primary inlet filter 110 and the phosphate removal filters 114,116,118.

Treated water from the treated water tank 134 is used to backwash the primary filter 110 and/or one or more of the phosphate removal filters 114,116,118. Conduits and associated pumps 136,138,140,142 are provided to ensure that the treated water is pumped through the primary filter 110 and the phosphate removal filters 114, 116, 118. The backwash from the primary filter 110 and/or the phosphate removal filters IE 1 1 0 097 -25114,116,118 is returned to the waste water treatment plant 102 via an outlet conduit 144.

It will be understood that the phosphate removal media in the phosphate removal filters 114, 116, 118 has a certain capacity to adsorb a particular amount ot phosphate after which it must be regenerated. That is to say, the phosphate removal media has to be intermittently flushed out with a regeneration solution to desorb and remove the phosphate ions from the phosphate removal media so that the phosphate removal media can be continued to be used in the effluent treatment assembly 100. It has been found that the phosphate removal media has a capacity to collect phosphate up to 1.8 g of phosphate per 1 kilogram of phosphate removal media at a level of 0.03 mg of phosphate per litre of treated effluent output from the one or more phosphate removal filters 114,116, 118. After 1.8 g of phosphate has been removed from the effluent per every kilogram of phosphate removal media, the regeneration solution must be passed through the phosphate removal media.

Typically, the regeneration solution will be a dilute alkaline solution. In this embodiment, the dilute alkaline solution, comprised of a certain percentage of a caustic agent such as Sodium Hydroxide (NaOH), otherwise known as caustic soda.

The amount of caustic agent in the regeneration solution will be in the range of 1% to 20% by volume, and is preferably lower than 16% by volume. In yet a further preferred embodiment, the percentage of caustic agent in the regeneration solution is between 2% and 3.5% by volume. The regeneration solution is used to remove the accumulated phosphate from the phosphate removal filters 114, 116, 118. The preferable contact time for the regeneration solution with the phosphate removing filter media in the phosphate removal filters 114, 116, 118 is between 1 and 3 minutes, and optimally 2 minutes.

It has been found that a preferable ratio of regeneration solution to phosphate removal media is between 5:1 and 5.5:1, and, preferably 7:1 and 8:1. Therefore, in a phosphate removal filter holding 100 litres of phosphate removal media, 700 litres to 800 litres is preferably passed through the phosphate removal filer to fully regenerate the phosphate removal media. Prior to each regeneration procedure, and between each regeneration procedures, the one or more phosphate removal filters 114, 116, 118 are backwashed for a period between 2 and 4 minutes, and preferably 3 IE 1 1 Ο 097 -26minutes. The backwash comprises water from the treated water discharge outlet 128.

A regeneration solution tank 146 is provided in the effluent treatment assembly 100 to act as a source of regeneration solution for the phosphate removal filters 114,116, 118. A pump 148 pumps the regeneration solution through a conduit 150 from the regeneration solution tank 146 to the phosphate removal filters 114, 116, 118. In an alternative embodiment, a pump sucks regeneration solution through the phosphate removal filters 114, 116, 118 so that any remaining effluent is removed from the phosphate removal filters 114, 116, 118 prior to the regeneration solution entering the phosphate removal filters 114,116,118. In this manner, the regeneration solution will not be diluted.

Once the regeneration solution has passed through the phosphate removal filters 114,116,118, the regeneration solution and the phosphate which has been removed from the filters 114,116, 118 travels along a conduit 152 into a sedimentation tank 156. A calcium-based substance, which will typically be the Calcium Chloride (CaCI2), is added to the sedimentation tank 156. The calcium-based substance is stored in a storage tank 158 and is pumped to the sedimentation tank 156 using a pump 160 and an associated conduit 162.

The calcium-based substance is stirred to form a bond with the phosphate which was removed from the phosphate removal filters 114, 116, 118 and forms into a sedimentation sludge 166 which settles at the bottom of the sedimentation tank 156.

The time taken for the calcium-based substance to bond with the phosphate and form into the sedimentation sludge 166 is in the range of 15 minutes to 60 minutes. Typically the amount of time taken has been found to be less than 30 minutes. A molar ratio of 2.7:1 of Ca to P has been found to be optimally effective.

Recovered regeneration solution 164 in the sedimentation tank 156 separates from a sedimentation sludge 166 as the sedimentation process takes place and the recovered regeneration solution 164 sits on top of the sedimentation sludge 166 in the sedimentation tank 156. The recovered regeneration solution 164 is passed back into the regeneration solution tank 146 via an upper outlet on the sedimentation tank 156, a conduit 168 and an associated pump 170. The Hydroxyapatite (Ca5(PO4)3OH) IE 1 1 0 097 -27which forms the sedimentation sludge at the bottom of the sedimentation tank 156 may be recovered through a lower outlet 172 of the sedimentation tank 156.

The Hydroxyapatite recovered from the sedimentation tank may be advantageously used as a fertiliser. In a preferred embodiment, the Hydroxyapatite is dehydrated and pelletised for use as a fertiliser.

The regeneration solution is fed from the sedimentation tank 156 and is passed back into the regeneration solution tank 146 for reuse in the effluent treatment process. A caustic agent level measurement device 174 determines if the recovered regeneration solution is suitable for reuse. A fresh regeneration solution source 176 can pass fresh regeneration solution into the regeneration solution tank 146 via conduit 180 using an associated pump 178 if required. The fresh regeneration solution mixes with the recovered regeneration solution in the regeneration solution tank 146 to form a regeneration solution which is suitable for passing through the phosphate removal filters 114, 116, 118 in order to regenerate the phosphate removal medium in the phosphate removal filters 114, 116, 118. Treated water from the treated water tank 134 may be also feed into the regeneration solution tank 146 via conduit 182 and an associated pump 142. In an alternative embodiment, fresh caustic agent (not shown) may be added to the regeneration solution tank 146 instead of fresh regeneration solution.

After the regeneration solution has been passed through the phosphate removal filters 114, 116,118, carbon dioxide (CO2) is passed through each of the phosphate removal filters 114,116,118 so as to reduce the pH level in the filters 114,116, 118 to a suitable level. The CO2 is supplied into each of the phosphate removal filters 114, 116, 118 in turn. The CO2 is supplied from a CO2 supply tank 184 and is subsequently discharged through the outlet oonduit 144. It will be understood that it is also envisaged to pass the CO2 through each of the phosphate removal filters 114, 116, 118 at the same time. In a preferred embodiment, only CO2 is passed through the phosphate removal filters 114,116,118 to reduce the pH level in the one or more phosphate removal filters 114, 116, 118 after the regeneration solution has been passed through them. Based on an alkalinity of 750mg/litre of caustic agent remaining in the phosphate removal filter, the effluent treatment assembly would require a volume of CO2 equal to or greater than 0.75% of the volume of the IE 1 1 0 097 -28phosphate removing filter media, in order to reduce the pH level in the filters 114, 116,118 from a pH ievel of 13 to a pH level of at least 9.

A pH level analyser 186 may be provided in order to monitor the pH level of each of the phosphate removal filters 114, 116, 118 in turn as the CO2 is passed through each of the phosphate removal filters 114, 116, 118 in turn. The pH level analyser 186 is located along the outlet conduit 144 so that the pH levels of each of the phosphate removal filters 114, 116, 118 may be determined as the CO2 that has passed through the phosphate removal filter 114,116,118 is discharged through the outlet conduit 144.

A control unit 188 is also provided in the effluent treatment assembly 100 to control a number of valves (not shown), pumps and various components of the effluent treatment assembly 100.

Referring to Figures 2 and 3, a pair phosphate removal filters 114,116 may be split internally into three separated media retaining column compartments, indicated by reference numerals 302, 304, 206, 308, 310, 312 for phosphate removal filters 114, 116 respectively. The separated media retaining column compartments are also indicated by reference letters A, B, and C for a first phosphate removal filter 114 and D, E and Ffor a second phosphate removal filter 116. Each of the separated media retaining column compartments 302, 304,206, 308, 310, 312 are fluidly connected in series by internal piping 314, 316, 318, 320 and external piping 326. It will be understood that all of the piping could be internal or external piping with appropriate valves (not shown) in place. Any number of compartments may be used, not necessarily three as is shown in Figure 3. A similar effect can be achieved by linking a plurality of column adsorption towers in series. The internal piping 314, 316, 318, 320 each comprise an inlet 322 and an outlet 324.

It will be generally understood that whilst the compartmentalisation of a filter, tank or column, allows for the advantage of reusing regeneration solution on a separate compartment of phosphate removing filter media, and thus advantageously remove, desorb and collect more phosphate ions than would be possible with any compartmentalised filter, the filters themselves may be connected in parallel and not necessarily in series as is shown in Figure 3. Moreover, during the filtration stage, the IE 11 Ο 097 -29compartments may work in parallel to each other, even within the same filter tower/column. Appropriate valves and other such controls as are well known in the art are required to achieve a serial/paraliel arrangement.

The table indicated by reference numeral 200 in Figure 2 shows that on a first pass of regeneration solution through the first and second filters 114, 116, 50% of the phosphate ions in media retaining column compartment A are removed, and no other phosphate ions are removed from any other media retaining column compartments B, C, D, E or F. On the second pass of regeneration solution through the first and second filters 114, 116, 25% of the phosphate ions in media retaining column compartment A are removed and 25% of the phosphate ions in media retaining column compartment B are removed. On the third pass of regeneration solution through the first and second filters 114, 116, 12% of the phosphate ions in media retaining column compartment A are removed and 38% of the phosphate ions in media retaining column compartment β are removed. On the fourth pass of regeneration solution through the first and second filters 114, 116, 6% of the phosphate ions in media retaining column compartment A are removed, 19% of the phosphate ions in media retaining column compartment B are removed and 25% of the phosphate ions in media retaining column compartment C are removed.

Therefore, as can be seen, the regeneration solution removes, at most, approximately half of the phosphate ions in a media retaining column compartment as the regeneration solution passes through. In total 16 passes of regeneration solution would be required to completely regenerate the first and second filters 114, 116 which would approximately be a ratio of 2.6:1 of regeneration solution to phosphate removal media in the compartments 302, 304, 206, 308, 310, 312 of the filters 114,116. As can be seen, this ratio is significantly less than if the regeneration solution was disposed of after a single pass through a single compartment 302, 304, 206, 308, 310, 312 which is typically in the range of 5:1 to 8:1. By running the regeneration solution through a plurality of serially linked compartments 302, 304, 206, 308, 310, 312, the regeneration solution has a greater effect on removing phosphate ions and the amount ratio of the volume of regeneration solution required to the volume of filter media is significantly reduced.

It should be noted that the percentages shown in Figure 2 are only representative of approximate phosphate ion removal percentages based on passing a filter bed IE 11 0 0 97 -30volume of regeneration solution through one of the one or more phosphate removal filters. As can be seen from Figure 2, only 93% of phosphate is removed from each of the compartments as it is considered to be uneconomical to pursue further removal of phosphate from the phosphate removing filter media due to the law of diminishing returns, in another embodiment, the regeneration solution may be passed through until substantially ail of the phosphate has been removed and desorbed from the phosphate removing filter media.

In a particular embodiment, the entire effluent treatment assembly 100 is enclosed within a housing 190. For example, the housing 190 may be a standard sized transport container. Although the sedimentation tank 156, the fresh regeneration solution source 176 and their associated conduits, are not shown to be within the housing 190 in Figure 1, it will be appreciated that in another embodiment, all the components of the effluent treatment assembly 100 are contained within the housing 190.

It will be appreciated that the various valves which allow the effluent, regeneration solution, calcium-based substance solution, sedimentation mixture in the sedimentation tank 156, sedimentation sludge 166, treated water and so on to flow around the effluent treatment assembly 100 as hereinbefore described have not then explicitly disclosed in Figure 1 but will be understood by the person skilled in the art to be implicitly disclosed in this specification.

In a further embodiment, it is envisaged that an untreated effluent, as in phosphate25 rich effluent may by-pass the effluent treatment assembly 100 and be mixed with treated effluent prior to being discharged as surface water so that a maximum legally allowable phosphate level can be achieved in the discharged surface water. This avoids unnecessary phosphate removal treatment and maximises the operating cost efficiency of the effluent treatment assembly 100.

Throughout the preceding description, it should be understood that the term “phosphate” may refer to either a chemical composition comprising phosphorus or to the chemical element phosphorus itself, and, that any reference to “phosphate” should be interpreted as such.

IE 1 1 0 0 97 -31 In this specification, the terms “comprise, comprises, comprised and com prising and the terms “include, includes, included and including, including all forms of grammatical variations, are all deemed totally interchangeable and should be afforded the widest possible interpretation.

The invention is not limited to the embodiments hereinbefore described and each of the terms used in the preceding specification should be afforded the widest possible interpretation. It will be appreciated that many of the features in all of the above described embodiments may be combined together to form further embodiments of the present invention.

Claims

1. An effluent treatment assembly for treating effluent by reducing phosphate content in the effluent, the assembly comprising a primary inlet filter for filtering 5 effluent received from an effluent source, one or more phosphate removal filters to treat the filtered effluent and a discharge outlet for discharging treated effluent into an environment, characterised in that, the one or more phosphate removal filters each comprise phosphate removing filter media, the phosphate removing filter media comprising a plurality of 10 macroporous ion exchange beads which have been each impregnated with an ion adsorption material.

2. An effluent treatment assembly as claimed in any of the preceding claims, wherein, the effluent treatment assembly further comprises a regeneration 15 solution tank which is connected to the one or more phosphate removal filters to provide a regeneration solution which is passed through the one or more phosphate removal filters; the regeneration solution comprises 2% to 3.5% caustic agent by volume. 20

3. An effluent treatment assembly as claimed in any of the preceding claims, wherein, the assembly further comprises a sedimentation tank which is connected to the one or more phosphate removal filters to receive a phosphateenriched regeneration solution which has passed through the one or more phosphate removal filters and has removed phosphate from the phosphate 25 removing filter media; and, a calcium chloride storage tank which is fluidly connected to the sedimentation tank to allow Calcium Chloride (CaCI 2 ) to be added to tiie phosphate-enriched regeneration solution so as to form a sedimentation mixture in the sedimentation tank; wherein, the sedimentation tank comprises an upper outlet to allow 30 recovered regeneration solution which has separated from the sedimentation mixture to be bled off and passed into the regeneration solution tank for re-use in the effluent treatment assembly, and, a lower outlet for releasing a sedimentation sludge. 35

4. An effluent treatment assembly, as claimed in any of the preceding claims, IE 1 1 0 097 -33wherein, the one or more phosphate removal filters comprise separated media retaining column compartments which are fluidly connected in series. An effluent treatment assembly as hereinbefore described with reference to the accompanying figures.