Process for removing active pharmaceutical ingredients from wastewater

Abstract

The present invention relates to a process for removing active pharmaceutical ingredients (API) from wastewater. Biological treatment and oxidation via ozonation, as well as suspended solids removal, is employed to ultimately reduce the concentration of API to an appropriate or acceptable level.

Description

[0001] PROCESS FOR REMOVING ACTIVE PHARMACEUTICAL INGREDIENTS FROM WASTEWATER

[0002] RELATED APPLICATIONS

[0003] This application claims priority to U.S. Provisional Patent Application Serial No. 63 / 568,199 filed on March 21 , 2024, which is incorporated herein by reference in its entirety.

[0004] FIELD OF INVENTION

[0005] The present invention relates to wastewater treatment systems and processes, and particularly to a wastewater treatment system and process that is configured to efficiently and effectively destroy or remove active pharmaceutical ingredients (API) from wastewater.

[0006] BACKGROUND OF THE INVENTION

[0007] It is difficult and challenging to efficiently and effectively remove API and other micropollutants from wastewater streams. Indeed, pharmaceutical residues or API typically pass through sewage treatment plants and end up in receiving water and sludge. While some conventional wastewater treatment technologies remove some API from wastewater, such conventional technologies are not likely to remove the API in wastewater down to regulatory or stringent permit limits. There are many processes that exist for micropollutant reduction. According to the removal mechanism, they can be categorized as following:

[0008] 1 . Adsorption processes: adsorption on activated carbon, using Powdered, Activated Carbon (PAC) or Granular Activated Carbon (GAC), adsorption on specific media as used for example within Macro-Porous Polymer Extraction (MPPE)

[0009] 2. Chemical oxidation using ozone, UV, hydrogen peroxide or a combination (collectively referred to as Advanced Oxidation Processes (AGP))

[0010] 3. High-pressure filtration such as nanofiltration (NF) and Reverse Osmosis (RO) membranes concentration processes 4. Biological processes: biological treatment using microorganisms

[0011] There is not a universal solution to handle all micropollutants. The treatment options available all have pros and cons. Some treatment processes show limited removal of micropollutants but may suffice in certain situations. Processes such as activated carbon adsorption, AOPs, RO may be more effective but have higher operating costs. Other treatment processes that concentrate the target compounds into a residual such as sludge, exhausted GAC / PAC, concentrate, or brine will require further handling. Another point of increasing interest is the fate of the micropollutants. Biological treatment in many cases can reach the mineralization of the targeted micropollutants, while chemical oxidation may transform the target molecule into another compound that may be less or more toxic than the parent compound (by-products) which, in the end, gives rise to problems and drawbacks. Biological treatment: advanced biological treatments Conventional activated sludge (CAS) systems are effective in reducing some micropollutants, mostly the easily degradable compounds. However advanced biological treatments generally achieve higher reduction rates than CAS. Membrane BioReactor (MBR): the combination of activated sludge and ultrafiltration membranes gives good reduction rates on a reasonable spectrum of micropollutants. In the activated sludge tank, the easily degradable compounds are oxidized by the biomass, then the membrane acts as a selective barrier and retains some organic molecules (macromolecules with size between 0.1 and 0.01 pm) which would not be retained on a clarifier in a CAS system.

[0012] Moving Bed Biofilm Reactor: eXeno™, this Veolia technology typically involves multiple MBBR reactors in series with conditions to encourage the development of specialized microorganisms in each reactor tank to target a variety of complex compounds. In the first stage, more easily degradable compounds are removed while the more difficult compounds are removed in the succeeding reactors. The low load conditions in late stages allow for the development of specific microorganisms capable of degrading the more complex compounds. However, a standalone MBBR biological process is often unable to meet stringent API permit limits or high removal rates required by industry.

[0013] Therefore, there is a need for an efficient and cost effective process for destroying or removing API in wastewater down to ultralow or stringent permit limits.

[0014] SUMMARY OF THE INVENTION

[0015] The present invention relates to a system and process that employs one or more MBBRs, a solid-liquid separator, and one or more ozone reactors, and which is designed to treat a wastewater stream containing API. The MBBR-technology relies on microorganisms, such as bacteria or micro-fungi, growing on carriers which are retained in the reactor. MBBR-technology allows for the development of biomass with significantly longer sludge retention times (SRT) compared to conventional systems. This encourages the development of slower growing organisms capable of removing difficult compounds.

[0016] Some of the aims of the present invention are to provide an MBBR-ozone process for reducing the concentrations of API in wastewater streams that: (1) maximizes API destruction rates with minimum ozone doses; (2) increases overall API removal efficiency and rates; and (3) defines the minimum, maximum and optimum ozone / total organic carbon ratios for cost effectively reducing API concentrations in wastewater streams to ultralow limits.

[0017] Typically, wastewater streams containing API also include suspended solids and inorganic and organic compounds that give rise to chemical oxygen demand (COD). The present invention entails a process for destroying API in a wastewater stream that strategically addresses the suspended solids and COD in ways where the presence of suspended solids and COD in the wastewater does not adversely impact the process of using ozone to destroy the API. In this regard, in one embodiment, an ozone reactor is located downstream from at least one MBBR and a solid-liquid separator. Hence, the MBBR addresses the COD (while typically removing some API) in the wastewater stream and the solid-liquid separator removes suspended solids from the wastewater stream before residual API in the wastewater stream is subjected to ozonation in the ozone reactor. This underlies one of the significant principles discovered by the inventors. That is, the efficiency and cost effectiveness of destroying residual API by ozonation is enhanced by removing suspended solids and chemical oxygen demand from the wastewater prior to attacking the residual API via ozonation.

[0018] A further discovery by the inventors relates to a method of determining efficient and cost effective ozone dosage requirements based on the concentration of total organic carbon (TOC) in the wastewater. Hence, the present invention entails monitoring or measuring the TOC concentration in the wastewater influent into an ozone reactor and based on the TOC concentration, determining the amount of ozone that is dosed into the wastewater in the ozone reactor. In other words, the ozone dosage is a function of TOC concentration in the wastewater.

[0019] In one embodiment, the present invention entails a method for treating the wastewater stream containing suspended solids, API, and other biodegradable inorganic and organic compounds. The method entails directing the wastewater into a first MBBR. After removing the suspended solids from the wastewater, the method entails directing the wastewater into an ozone reactor and ozonating the wastewater therein to reduce the concentration of API in the wastewater.

[0020] In another embodiment, the present invention entails a method of treating wastewater containing suspended solids and API and comprising: a. directing the wastewater into an MBBR; b. biologically treating the wastewater to remove biodegradable inorganics and organics a portion of the API in the wastewater, leaving the wastewater with residual API, which normally are complex and non-biodegradable organics; c. after treating the wastewater in the MBBR, directing the wastewater to a solidliquid separator and removing the suspended solids from the wastewater; d. after removing the suspended solids from the wastewater, directing the wastewater containing the residual API to an ozone reactor; e. reducing the concentration of residual API in the wastewater by: i. monitoring the TOC concentration in the wastewater in the ozone reactor or at a point upstream of the ozone reactor; ii. based on the TOC concentration in the wastewater, determining an ozone dosage and dosing the wastewater in the ozone reactor accordingly; and ill. wherein dosing the wastewater in the ozone reactor results in ozonating the residual API in the wastewater, which in turn reduces the concentration of the residual API in the wastewater.

[0021] One embodiment of the present invention includes a method of treating a secondary or pre-treated wastewater effluent comprising active pharmaceutical ingredients (API), suspended solids, and biodegradable inorganic and organic compounds, comprising: directing the secondary or pre-treated wastewater effluent (wastewater) into a first moving bed bioreactor (MBBR); reducing the chemical oxygen demand (COD) of the wastewater in the first MBBR by biodegrading the inorganic and organic compounds in the wastewater; biodegrading a portion of the API in the wastewater in the first MBBR, leaving a residual portion of the API in the wastewater; after treating the wastewater in the first MBBR, directing the wastewater to a downstream solids-liquid separator and removing the suspended solids from the wastewater; after removing the suspended solids from the wastewater, directing the wastewater containing the residual API to an ozone reactor located downstream from the first MBBR and the solids-liquid separator; reducing the concentration of the residual API in the wastewater in the ozone reactor by: i. measuring the total organic carbon (TOC) concentration in the wastewater at a point downstream of the first MBBR and upstream from the ozone reactor; ii. using the measured TOC concentration in the wastewater to determine an ozone dosage rate for the ozone reactor based on dosing the wastewater with approximately 3-5 Mg O3per mg of TOC in the wastewater; ill. after determining the ozone dosage rate, dosing the wastewater in the ozone reactor at the determined ozone dosage rate; and iv. wherein dosing the wastewater in the ozone reactor results in ozonating the residual API in the wastewater, which in turn reduces the concentration of the residual API in the wastewater.

[0022] Another embodiment of the present invention includes a method of treating a secondary or pre-treated wastewater effluent comprising active pharmaceutical ingredients (API), suspended solids, and biodegradable inorganic and organic compounds, comprising: directing the secondary or pre-treated wastewater effluent (wastewater) into a first moving bed bioreactor (MBBR); reducing the chemical oxygen demand (COD) of the wastewater in the first MBBR by biodegrading the inorganic and organic compounds in the wastewater; biodegrading a portion of the API in the wastewater in the first MBBR, leaving a residual portion of the API in the wastewater; after treating the wastewater in the first MBBR, directing the wastewater containing the residual API into a first ozone reactor; reducing the concentration of the residual API in the wastewater in the first ozone reactor by: i. measuring a first total organic carbon (TOC) concentration in the wastewater at a first point downstream of the first MBBR and upstream of the first ozone reactor; ii. using the first measured TOC concentration to determine a first ozone dosage rate based on dosing the wastewater with approximately 5-10 Mg O3 per mg of TOC in the wastewater; ill. after determining the first ozone dosage rate, dosing the wastewater in the first ozone reactor at the determined first ozone dosage rate; and iv. wherein dosing the wastewater in the first ozone reactor results in ozonating the residual API in the wastewater, which in turn reduces the concentration of the residual API in the wastewater but wherein there remains a further residual API concentration in the wastewater in the first ozone reactor; after reducing the residual API concentration in the first ozone reactor, directing the wastewater containing the further residual API to a second MBBR and biologically treating the wastewater and the further residual API in the second MBBR; after treating the wastewater and further residual API in the second MBBR, directing the wastewater to a downstream solids-liquid separator and removing the suspended solids from the wastewater; after removing the suspended solids from the wastewater, directing the wastewater containing the further residual API to a second ozone reactor located downstream from the second MBBR and the solids-liquid separator; reducing the concentration of the further residual API in the wastewater in the second ozone reactor by: i. measuring a second TOC concentration in the wastewater at a second point downstream of the second MBBR and upstream from the second ozone reactor; ii. using the second measured TOC concentration to determine a second ozone dosage rate for the second ozone reactor based on dosing the wastewater with approximately 3-5 Mg O3 per mg of TOC in the wastewater; iii. after determining the second ozone dosage rate for the second ozone reactor, dosing the wastewater in the second ozone reactor at the determined second ozone dosage rate; and iv. wherein dosing the wastewater in the second ozone reactor results in further ozonating the further residual API in the wastewater, which in turn reduces the concentration of the further residual API in the wastewater.

[0023] Other objects and advantages of the present invention will become apparent and obvious from a study of the following description and the accompanying drawings which are merely illustrative of the invention.

[0024] BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 is a schematic illustration of a first process for removing residual API from a wastewater stream containing API where the process entails treating the wastewater stream in a first MBBR, followed by removing suspended solids from the wastewater in a solid-liquid separator, and finally treatment in an ozone reactor.

[0026] Figure 2 is a schematic illustration of a second process that is similar in many respects to the process depicted in Figure 1 except in this case the wastewater stream is subjected to treatment in two MBBRs upstream of the solid-liquid separator.

[0027] Figure 3 depicts a third process for destroying or reducing the concentration of API in a wastewater stream where the process includes two MBBRs, a solid-liquid separator, and two ozone reactors.

[0028] DESCRIPTION OF EXEMPLARY EMBODIMENTS

[0029] With further reference to the drawings, various processes shown therein include one or more MBBRs, a solid-liquid separator, and one or more ozone reactors, all used to treat wastewater streams that include API, suspended solids, and inorganic and organic compounds. Before discussing the various processes shown in Figures 1 -3 in detail, it may be beneficial to briefly review the basic structure and function of MBBRs, solid-liquid separators, and ozone reactors.

[0030] Details of the MBBR and the processes performed therein are not dealt with here because such is not per se material to the present invention. Furthermore, MBBRs and the processes carried out therein are well known and appreciated by those skilled in the art. Suffice it to say that an MBBR process is an attached growth biological treatment process. That is, microorganisms specializing in the wide variety of complex compounds are attached to a medium which is referred to as a biofilm carrier. This encourages the development of slower growing organisms capable of removing difficult compounds.

[0031] Biofilm carriers are kept suspended in the wastewater by a diffused aeration system for an aerobic process or by a mechanical mixing system for an anoxic process. In this case, the MBBR functions to biodegrade inorganic and organic compounds and during the course of the processes shown in Figures 1-3 typically biodegrade some API. However, the aim of the present invention is to provide a total system and process that will destroy or remove API to extreme low permit limits that cannot generally be obtained solely through MBBR treatment. In any event, wastewater contained in an MBBR is generally sufficiently mixed and flows continuously through the MBBR. Generally, MBBRs include an aeration system that supplies air from a source through one or more air diffusers located in the bottom of the MBBR. From the air diffusers, the air is evenly distributed throughout the MBBR.

[0032] Various types of solid-liquid separators can be employed in the present processes. Three examples are: (1) disc filters; (2) ballasted flocculation systems; and (3) a solid-liquid separation system comprising both a disc filter and a ballasted flocculation system. Disc filters for removing suspended solids from wastewater streams are known and appreciated by those skilled in the art. For a more detailed understanding and appreciation for disc filters, one is referred to the disclosure found in U.S. Patent 8,961 ,785, the disclosure of which is incorporated herein by reference.

[0033] An example of a ballasted flocculation system is a system marketed by Veolia Water

[0034] Technologies under the brand name “Actiflo”. Generally, a ballasted flocculation process is a specialized method used for solid-liquid separation. It involves adding a dense, inert material (the “ballast”), such as sand, to the wastewater along with a coagulant and flocculant. These chemicals cause small particles and contaminants, i.e. suspended solids, to clump together into larger aggregates called flocs. The ballast material helps to increase the settling velocity of the flocs, allowing them to settle more rapidly in a sedimentation tank. This speeds up the separation process, resulting in removing suspended solids from an effluent.

[0035] An ozone reactor is a process component that can be used in a wastewater treatment system to generate and inject ozone into the wastewater for various purification purposes. Ozone is a powerful oxidizing agent and is effective in water and wastewater treatment for oxidizing organic and inorganic substances. In the case of the present invention, one or more ozone reactors are employed to degrade residual API that remains in the wastewater after treatment in one or more MBBRs. Ozone injected into the wastewater readily reacts with complex slowly or non-biodegradable organic compounds, including API, present in the wastewater. When ozone comes into contact with the API, it reacts with the chemical bonds within molecules, breaking them apart and oxidizing the compounds. As the ozone oxidizes the API, it transforms them into smaller, less complex molecules. In some cases, this process can completely mineralize the API, converting them into carbon dioxide, water, or other harmless by-products.

[0036] Now turning to Figure 1 , there is shown a process for removing API from a wastewater stream. The system employed generally includes a single stage MBBR coupled with a solid-liquid separator which is followed by an ozonation process occurring in an ozone reactor. The MBBR biodegrades inorganic and organic compounds and in doing so substantially reduces the COD of the wastewater. Likewise, the MBBR biologically reduces a substantial portion of the API in the wastewater. However, the wastewater effluent leaving the MBBR typically includes residual amounts of API. In order to reduce the API concentrations to ultralow levels, the process shown in Figure 1 is designed to achieve this downstream of the MBBR. As noted above, one of the discoveries by the inventors is that the position in the process where residual API is addressed is important, especially with respect to systems and processes that address COD and the removal of suspended solids. Indeed, it was determined that residual API can be best addressed from an efficiency and cost perspective after COD has been reduced and suspended solids have been removed from the wastewater stream. Hence, in the process depicted in Figure 1 , the effluent from the MBBR is directed to ta solid-liquid separator where suspended solids are removed from the wastewater stream. As discussed above, the solid-liquid separation process can be carried out by various devices, such as a disc filter, ballasted flocculation system, or a combination of the two. After the suspended solids have been removed from the wastewater stream, the wastewater including residual amounts of API is directed into the ozone reactor. Here, ozone is dispersed throughout the wastewater in the ozone reactor, which effectively destroys or further reduces API concentration in the wastewater.

[0037] One of the challenges faced by the inventors was that of developing a means of determining an optimum amount of ozone dosage for the wastewater in the ozone reactor. An optimum amount of ozone is an amount that minimizes the ozone dosage, and at the same time reduces residual API concentration to a selected level. It was determined that an optimum ozone dosage can be a function of TOC in the wastewater. In this regard, the inventors discovered that the optimum ozone dosage for the Figure 1 configuration is about 3-5 mg Oa / mg TOC at 30 minutes HRT HRT of the MBBR is between 4-6 hours, depending on the wastewater temperatures.

[0038] The process depicted in Figure 1 and discussed above is ideal or best suited for secondary effluents that: include low to medium biodegradable and slowly biodegradable carbon sources; include high residual API concentrations; require medium to low API removal rates.

[0039] Turning to Figure 2, a second embodiment of the API process is shown therein. It is similar to the process depicted in Figure 1 and discussed above, but includes two MBBRs in series which are referred to as Stage 1 MBBR and Stage 2 MBBR. Here, the optimum ozone dosage is again about 3-5 mg Oa / mg TOC at 20 minutes HRT. The HRT of each MBBR stage is between 4-6 hours so that the total HRT for the wastewater in this embodiment is between 8-12 hours, again depending on wastewater temperatures. This process is ideal for secondary effluents that: include some residual readily biodegradable and medium biodegradable carbon source; include a high residual API concentration; require high API removal rate.

[0040] Turning to Figure 3, a third embodiment for the process for removing API from a wastewater stream is depicted therein. This process configuration is similar to that depicted in Figure 2 and discussed above except that a second ozone reactor is interposed between the first and second MBBR stages. The purpose of the ozone reactor positioned between the two MBBRs is to break down slowly biodegradable COD and some of the API for better removal rates in the stage 2 MBBR. As discussed above, the effluent from the second stage MBBR is subjected to a solid-liquid separation process where suspended solids in the wastewater are removed. Since the effluent from the solid-liquid separator includes substantially less suspended solids compared to the suspended solids concentration in the effluent from the first stage MBBR, the optimum ozone dosage for the two ozone reactors may vary. Generally speaking, in many cases the ozone dosage for the first ozone reactor, the one disposed between the two MBBRs, is greater than the ozone dosage for the final ozone reactor. It was found, generally speaking, that the optimum ozone dosage for the first ozone reactor is about 5-10 mg O3 / mg TOC at 30 minutes HRT while the optimum ozone dosage for the final or second ozone reactor is about 3-5 mg O s / mg TOC at 30 minutes HRT. Again, HRT for each of the MBBR stages is approximately 4-6 hours so that the total HRT is between approximately 8 and 12 hours, depending on the wastewater temperatures.

[0041] This particular process and configuration is ideal for secondary effluents that: include relatively high biodegradable and medium biodegradable carbon sources; include relatively low solids concentration from upstream treatments; include high residual API concentrations; require very high API removal rates.

[0042] The inventors have conducted a number of tests comparing API removal rates for a purely biological process (MBBR) on the one hand and an ozonation process, such as that shown in and depicted in the drawings. Table 1 appearing below shows these results.

[0043] Table 1 : API Removal Results: MBBR vs MBBR + O3

[0044] For many of the API species the use of the present process (biological treatment followed by solid-liquid separation, followed by ozonation) substantially increased API removal rate. For example, in the case of Piroxicam, the test reveals an average reduction rate of 85.54% using a purely biological process. However, when the process of the present invention was employed using an MBBR, followed by a solid-liquid separation which was followed with ozonation, the removal rate for Piroxicam was increased to 99.78%. These test results indicate that biological treatment alone is not very effective for some API species, but that ozonation treatment according to the processes shown in Figures 1-3 is more effective in reducing the concentration of these API species.

[0045] Thus, it is appreciated that the present invention is directed to a cost effective and efficient process for removing API, and particularly residual API, from wastewater that employs one or more MBBRs, a solid-liquid separation step, and one or more stages of ozonation. One or more MBBRs biologically treat the wastewater and in doing so biodegrade inorganic and organic compounds in the wastewater. But also, the one or more MBBRs can biodegrade substantial amounts of certain API species. However, MBBRs and the processes performed therein are not efficient in biologically degrading some API species. This means that the effluent from one or more upstream MBBRs will typically include significant residual amounts of API. The amount of residual API will depend on a number of factors, such as the identity of API species in the wastewater, the number of MBBRs employed, the efficiency of the MBBRs, etc. Thus, the final ozonation process employed in the processes depicted in Figures 1-3 effectively form a polishing operation in destroying or reducing all or most of the residual API.

[0046] One of the significant aspects of the present invention is the recognition and discovery that the efficiency of breaking down API compounds with ozone is increased and made cost effective by removing suspended solids and substantial amounts of inorganic and organic compounds from the wastewater prior to a final ozonation step. Hence, this underlies the rationale of utilizing one or more MBBRs and a solid-liquid separator upstream of a final ozonation process.

[0047] There are many advantages of the process described above. The process: encourages the development of slower-growing microorganisms capable of removing difficult and complex compounds in MBBR reactor(s); maximizes slowly or non-biodegradable pharmaceutical destruction rate through the ozonation process; - maximizes the overall pharmaceutical removal rate through the processes described above; minimizes ozone dosage as measured by the ratio of ozone to TOC; defines the optimum ozone dosage as determined by the ratio of ozone to TOC in the wastewater. The present invention may, of course, be carried out in other specific ways than those herein set forth without departing from the scope and the essential characteristics of the invention. The present embodiments disclosed herein are therefore to be construed in all respects as illustrative and not restrictive and all changes coming within the meaning and equivalency range of the appended claims are intended to be embraced therein.

Claims

CLAIMSWhat is claimed is:1 . A method of treating a secondary or pre-treated wastewater effluent comprising active pharmaceutical ingredients (API), suspended solids, and biodegradable inorganic and organic compounds, comprising: directing the secondary or pre-treated wastewater effluent (wastewater) into a first moving bed bioreactor (MBBR); reducing the chemical oxygen demand (COD) of the wastewater in the first MBBR by biodegrading the inorganic and organic compounds in the wastewater; biodegrading a portion of the API in the wastewater in the first MBBR, leaving a residual portion of the API in the wastewater; after treating the wastewater in the first MBBR, directing the wastewater to a downstream solids-liquid separator and removing the suspended solids from the wastewater; after removing the suspended solids from the wastewater, directing the wastewater containing the residual API to an ozone reactor located downstream from the first MBBR and the solids-liquid separator; reducing the concentration of the residual API in the wastewater in the ozone reactor by: i. measuring the total organic carbon (TOC) concentration in the wastewater at a point downstream of the first MBBR and upstream from the ozone reactor; ii. using the measured TOC concentration in the wastewater to determine an ozone dosage rate for the ozone reactor based on dosing the wastewater with approximately 3-5 Mg O3per mg of TOC in the wastewater; ill. after determining the ozone dosage rate, dosing the wastewater in the ozone reactor at the determined ozone dosage rate; andiv. wherein dosing the wastewater in the ozone reactor results in ozonating the residual API in the wastewater, which in turn reduces the concentration of the residual API in the wastewater.

2. The method of claim 1 including maintaining the hydraulic residence time (HRT) in the ozone reactor at approximately 30 minutes and maintaining the HRT of the first MBBR at between 4-6 hours.

3. A method of treating a secondary or pre-treated wastewater effluent comprising active pharmaceutical ingredients (API), suspended solids, and biodegradable inorganic and organic compounds, comprising: directing the secondary or pre-treated wastewater effluent (wastewater) into a first moving bed bioreactor (MBBR); reducing the chemical oxygen demand (COD) of the wastewater in the first MBBR by biodegrading the inorganic and organic compounds in the wastewater; biodegrading a portion of the API in the wastewater in the first MBBR, leaving a residual portion of the API in the wastewater; after treating the wastewater in the first MBBR, directing the wastewater containing the residual API into a first ozone reactor; reducing the concentration of the residual API in the wastewater in the first ozone reactor by: i. measuring a first total organic carbon (TOC) concentration in the wastewater at a first point downstream of the first MBBR and upstream of the first ozone reactor; ii. using the first measured TOC concentration to determine a first ozone dosage rate based on dosing the wastewater with approximately 5-10 Mg O3 per mg of TOC in the wastewater;iii. after determining the first ozone dosage rate, dosing the wastewater in the first ozone reactor at the determined first ozone dosage rate; and iv. wherein dosing the wastewater in the first ozone reactor results in ozonating the residual API in the wastewater, which in turn reduces the concentration of the residual API in the wastewater but wherein there remains a further residual API concentration in the wastewater in the first ozone reactor; after reducing the residual API concentration in the first ozone reactor, directing the wastewater containing the further residual API to a second MBBR and biologically treating the wastewater and the further residual API in the second MBBR; after treating the wastewater and further residual API in the second MBBR, directing the wastewater to a downstream solids-liquid separator and removing the suspended solids from the wastewater; after removing the suspended solids from the wastewater, directing the wastewater containing the further residual API to a second ozone reactor located downstream from the second MBBR and the solids-liquid separator; reducing the concentration of the further residual API in the wastewater in the second ozone reactor by: i. measuring a second TOC concentration in the wastewater at a second point downstream of the second MBBR and upstream from the second ozone reactor; ii. using the second measured TOC concentration to determine a second ozone dosage rate for the second ozone reactor based on dosing the wastewater with approximately 3-5 Mg O3 per mg of TOC in the wastewater; iii. after determining the second ozone dosage rate for the second ozone reactor, dosing the wastewater in the second ozone reactor at the determined second ozone dosage rate; andiv. wherein dosing the wastewater in the second ozone reactor results in further ozonating the further residual API in the wastewater, which in turn reduces the concentration of the further residual API in the wastewater.

4. The method of claim 3 including maintaining the HRT in each of the first and second ozone reactors at approximately 30 minutes and maintaining the total HRT of the first and second MBBRs at between 8 and 12 hours.

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