BACKGROUND OF THE INVENTION

[0001] Field. This invention relates to wastewater treatment methods to produce Class A Biosolids, and recovered wastewaters suitable for land application or open stream discharge. More particularly, it relates a wastewater treatment method and apparatus for removing suspended solids from wastewater inflow streams and/or conventional process liquid streams to reduce loads on bioreactors, and then, sulfurous acid treats the removed solids containing heavy metals, and phosphorous, at a pH and dwell time to disinfect, acid leach heavy metals into solution for subsequent alkaline precipitation removal, and self-agglomerate the suspended solids for subsequent chemical dewatering to create a Class A biosolid. The separated liquid fraction is then bio remediated to reduce nitrogen, phosphorous and BOD, and then disinfected creating a Tertiary treated recovered wastewater for saline and pl-l adjustment using acid/base addition to create a custom recovered wastewater suitable for land application or open stream discharge.

[0002] State of the Art. Most large municipal systems employ a series of settling ponds sequentially concentrating the solids contained in wastewater either with or without polymers for separation from liquids via mechanical separation means, such as belt presses. To produce a clean effluent that can be safely discharged to watercourses, wastewater treatment operations use distinct stages of treatment to remove harmful contaminants. Preliminary wastewater treatment usually involves gravity sedimentation of screened wastewater to remove settled solids, Secondary wastewater treatment is accomplished through a biological process, removing biodegradable material This treatment process uses microorganisms to consume dissolved and suspended organic matter, producing carbon dioxide and other by- products. The removal capacity of these secondary bioreactors is dependent upon the influent suspended solids and dissolved solids and nutrient concentration loads placed on them. Tertiary or advanced treatment is used when extremely high-quality effluent is required with reduced solid residuals collected through tertiary treatment consisting mainly of chemicals added to clean the final effluent, which are reclaimed before discharge, and therefore not incorporated into bio-solids.

[0003] Wastewater treatment plants employ different types of bioreactors using microbes and bacteria to reduce BOD, nitrogen and phosphorous compounds contained in wastewater influent, and separate the suspended solids into Class A arid Class B Biosolids. To ensure that biosolids applied to the land do not threaten public health, the U.S. Environmental Protection Agency (EPA) created the 40 CFR Part 503 Rule. It categorizes biosolids as Class A or B, depending on the levels of pathogenic organisms in the material, and describes specific processes to reduce pathogens to these levels.

[0004] The 503 rule also requires heavy metals reduction and "vector attraction reduction" (VAR) - reducing the potential for spreading of infectious disease agents by vectors (i.e., flies, rodents and birds) - and spells out specific management practices, monitoring frequencies, record keeping and reporting requirements. Incineration of biosolids is also covered in the regulation.

[0005] As stated in www.water.siemens.com/en/applications/water _^ and wastewater...,

[0006] "Class A biosolids contain minute levels of pathogens. To achieve Class A certification, biosolids must undergo heating, composting, digestion or increased pH that reduces pathogens to below detectable levels. Some treatment processes change the composition of the biosolids to a pellet or granular substance, which can be used as a commercial fertilizer. Once these goals are achieved, Class A biosolids can be land applied without any pathogen-related restrictions at the site. Class A biosolids can be bagged and marketed to the public for application to lawns and gardens.

[0007] Class B biosolids have less stringent standards for treatment and contain small but compliant amounts of bacteria. Class B requirements ensure that pathogens in biosolids have been reduced to levels that protect public health and the environment and include certain restrictions for crop harvesting, grazing animals and public contact for ail forms of Class B biosolids. Class B biosolids similarly undergo heating, composting, digestion or increased pH processes before leaving a wastewater treatment plant. This semi-solid material can receive further treatment when exposed to the natural environment as a fertilizer, where heat, wind and soil microbes naturally stabilize the biosolids.

[0008] The biosolids rule spells out specific treatment processes and treatment conditions that must be met for both A or B classifications.

[0009] Technologies that can meet Class A standards include thermal treatment methods like composting, heat drying, heat treatment, thermophilic (heat generating) aerobic digestion and pasteurization. Class A technologies are known as PFRP - Processes that can Further Reduce Pathogens. The technologies must process the biosolids for a specific length of time at a specific temperature.

[0010] Composting. This is an environmentally friendly way to recycle the nutrients and organic matter found in wastewater solids. Composting systems turn wastewater biosolids, sawdust, yard waste and wood chips into high-quality compost. As the material decomposes, oxygen filters through the compost site, releasing water, heat and carbon dioxide. This process helps dry the organic material, while the generated heat increases the rate of decomposition and kills pathogens.

[0011] Heat Drying. This process applies direct or indirect heat to reduce the moisture in biosolids. It eliminates pathogens, reduces volume and results in a product that can be used as a fertilizer or soil amendment. Because dryers produce a 90 percent dry material, additional VAR is not required.

[0012] Digestion. In ATAD (autothermal thermophilic aerobic digestion) systems, biosolids are heated to 131°F to 140°F (55°C to 60°C) and aerated for about 10 days. This autothermal process generates its own heat, and reduces volume. The result is a high-quality Class A product acceptable for reuse as a liquid fertilizer.

[0013] Pasteurization. Pasteurization produces a Class A material When the biosolids are heated to at least 158°F (70°C) for 30 minutes. This extreme heat kills pathogens in the organic matter. When followed by anaerobic digestion, the VAR is attained and the biosolids can be land applied with minimal restrictions. The majority of the energy used in the pasteurization process is recovered with an innovative heat exchanger system and used to maintain the proper temperature in downstream anaerobic digesters.

[0014] The actual requirements for Class A Biosolids are spelled out in 40 CFR Part 503 issued in 1993, EPA entitled "Standards for the Use and Disposal of Sewage Sludge". This rule defined the management practices and numerical criteria for the three major use and disposal options - land application, incineration and surface disposal. In addition to limiting where and when biosolids can be applied, the rule requires processes to kill pathogens and strictly limits amounts of metals that can be applied to any piece of land.

[0015] According to Siemen's, there is more to biosolids than achieving Class A or Class B status. Effective biosolids management systems feature efficient thickening, dewatering and transportation processes to reduce moisture and convey and store the dewatered "cake." Without reliable thickening, dewatering and handling technologies, biosolids management would be a more difficult and expensive proposition.

[0016] Thickenings To thicken or concentrate biosolids (in excess of 5 to 6 percent solids), Siemens Water Technologies offers a variety of systems, depending on biosolids characteristics and results desired. Among these are gravity belt and rotary drum thickeners, centrifuges, dissolved air flotation thickeners, and gravity thickeners.

[0017] Dewatering. For dewatering, they provide belt presses and centrifuges, which are capable of producing biosolids cake of 25 to 35 percent solids. Siemen's line of filter presses can achieve solids levels as high as 45 percent. The J-Vap® system as well as direct and indirect drying systems can dry biosolids in excess of 90 percent solids.

[0018] Biosolids Handling. Siemen's biosolids handling capabilities include belt conveyors, shafted and shaftless screw conveyors, and bucket elevators as well as a wide range of live bottom silos and hoppers for sludge collection and storage. They also provide biosolids mixing and pumping equipment.

[0019] The 40 CFR § 503.13 Pollutant limits are as follows: [0020] (a) Sewage sludge. (1) Bulk sewage sludge or sewage sludge sold or given away in a bag or other container shall not be applied to the land if the concentration of any pollutant in the sewage sludge exceeds the ceiling concentration for the pollutant in Table 1 of §503.13.

[0021] (2) If bulk sewage sludge is applied to agricultural land, forest, a public contact site, or a reclamation site, either:

[0022] (i) The cumulative loading rate for each pollutant shall not exceed the cumulative pollutant loading rate for the pollutant in Table 2 of §503.13; or

[0023] (ii) The concentration of each pollutant in the sewage sludge shall not exceed the concentration for the pollutant in Table 3 of §503.13.

[0024] (3) If bulk sewage sludge is applied to a lawn or a home garden, the concentration of each pollutant in the sewage sludge shall not exceed the concentration for the pollutant in Table 3 of §503.13.

[0025] (4) If sewage sludge is sold or given away in a bag or other container for application to the land* either:

[0026] (i) The concentration of each pollutant in the sewage sludge shall not exceed the concentration for the pollutant in Table 3 of §503.13 ; or

[0027] (ii) The product of the concentration of each pollutant in the sewage sludge and the annual whole sludge application rate for the sewage sludge shall not cause the annual pollutant loading rate for the pollutant in Table 4 of §503.13 to be exceeded. The procedure used to determine the annual whole sludge application rate is presented in appendix A of this part.

|0028] (b) Pollutant concentrations and loading rates— sewage sludge— (1) Ceiling concentrations.

10029] Table 1 of §503.13— Ceiling Concentrations

'Dry weight basis.

(2) Cumulative pollutant loading rates.

[0030] Table 2 of §503.13— Cumulative Pollutant Loading Rates

(3) Pollutant concentrations,

[0031] Table 3 of §503.13— Pollutant Concentrations

'Dry weight basis.

(4) Annual pollutant loading fates.

[0032] Table 4 of §503.13— Annual Pollutant Loading Rates

Annual pollutant loading rate (kilograms per hectare per 365 day

Pollutant

period)

[0033] (c) Domestic septage. The annual application rate for domestic septage applied to agricultural land, forest, or a reclamation site shall not exceed the annual application rate calculated using equation (1),

10034] Where:

AAR=AnnuaI application rate in gallons per acre per 365 day period.

N=Amount of nitrogen in pounds per acre per 365 day period needed by the crop of vegetation grown on the land. [58 FR 9387, Feb. 19, 1993, as amended at 58 FR 9099, Feb. 25, 1994; 60 FR 54769, Oct. 25, 1995]

[0035] § 503.32 Pathogens.

[0036] (a) Sewage sludge—Class A. (1) The requirement in §503.32(a)(2) and the requirements in either §503.32(a)(3), (a)(4), (a)(5), (a)(6), (a)(7), or (a)(8) shall be met for a sewage sludge to be classified Class A with respect to pathogens. These standards vary based on time of application, type of land application for consumable crops vs. grasses and landscaping. Generally, current Class A regulations vary, but require fecal coliform in the sewage sludge be less than 1000 Most Probable Number (MPN) per gram of total solids (dry weight basis) or the density of Salmonella sp. Bacteria in the sewage sludge shall be less than 3 MPN at the time the sewage sludge is used or disposed or at the time the sewage sludge is prepared for sale or given away in a bag or other container for application to the land. The time of measurement thus varies, based on type and time of application, time of storage, temperature above 50 degrees Celsius or higher of the sewage sludge, percentage of solids above 7 percent, density of viable helminthes ova, time exposed to air, etc.

[0037] When the density of viable helminthes ova in the sewage sludge prior to pathogen treatment is equal to or greater than one per four grams of total solids (dry weight basis), the sewage sludge is Class A with respect to viable helminthes ova when the density of viable helminthes ova in the sewage sludge after pathogen treatment is less than one per four grams of total solids (dry weight basis). [0038] Other methods to condition sewage sludge that is used or disposed shall be treated in a process that is equivalent to a Process to Further Reduce Pathogens, as determined by the permitting authority .

[0039] (b) Sewage sludge— Class B. (1) (i) The requirements in either §503.32(b) (2), (b) (3), or (b) (4) shall be met for a sewage sludge to be classified Class B with respect to pathogens.

[0040] (ii) The site restrictions in §503.32(b) (5) shall be met when sewage sludge that meets the Class B pathogen requirements in §503.32(b) (2), (b) (3), or (b) (4) is applied to the land.

[0041] These conventional Class A Biosolids treatment methods are generally employed after a biological reactor reduces nitrogen and phosphorus producing WAS. To reduce the remaining WAS and remaining biosolids, anaerobic digestion is used to reduce biosolids mass. Anaerobic digestion methods produce undesirable odors and greenhouse gas emissions. The resultant biosolids are then treated using energy intensive applications to achieve rapid disinfection, or involve composting taking a long time for biodegradation. The wastewater treatment method described below provides a low energy treatment method to rapidly dewater and disinfect biomass with few heavy metals, containing less than 10% water by weight, and biosolids with a BTU content approximating that of wood chips suitable for either land application or burning.

[0042] SUMMARY OF THE INVENTION

[0043] The present method and apparatus is a wastewater treatment method for wastewater streams and/or conventional wastewater treatment plant process liquid streams containing suspended solids, pathogens, BOD, COD, nitrogen compounds, phosphorous, arid PPCPs. It comprises removing all or a portion of the suspended solids in influent wastewater streams and/or conventional wastewater treatment plant process liquid streams to form a liquid steam with reduced BOD, COD, and suspended solids suitable for supporting bacteria and microbe bioremediation of nitrogen, phosphorous, BOD, and other nutrients in a bioreactor. If there are not sufficient nutrients in the screened influent for bioremediation, some of the raw influent may be sent directly to the bioreactor selected to meet wastewater treatment plant effluent discharge standards. [0044] The separated suspended solids are sent to a solids treatment zone (open pond, tanks, containers, etc.) for admixing with waste activated sludge (WAS) and/or return activated sludge (RAS) from bioreactors. The liquid stream with reduced solids, COD, and BOD is sent to a bioreactor [aerated and anaerobic ponds, sequential batch reactors (SBRs), biological nutrient reduction (BNRs) reactors, etc.] selected to bio remediate and remove nitrogen, phosphorous, and nutrients producing secondary treated Waters to the degree required to meet wastewater treatment plant discharge requirements. These bioreactors generate different return activated sludge (RAS) and waste activated sludge (WAS), which are sent to the solids treatment zone. [0045] A portion of the liquid stream is diverted and injected with SO? to form a sulfurous acid solution with free SO2, sulfites and bisulfites suspended. The sulfurous acid is added to the suspended solids and WAS/RAS in the solids treatment zone. The ratio of sulfurous acid to solids varies based on the nature of the separated solids. For example, jar settling tests at the Montalvo Municipal Improvement District indicated that the sulfurous acid addition is approximately twice the amount of WAS/RAS at a pH and dwell time to:

[0046] i. disinfect and self-agglomerate the suspended solids and WAS/RAS, [0047] ii. acid leach heavy metals contained in and on the suspended solids and WAS into solution for subsequent removal and separation, and

[00481 iii. condition the suspended solids and WAS/RAS for subsequent dewatering by shedding water upon separation and drying leaving a sulfurous acid leachate, [0049] The S<¾ treated suspended solids and WAS/RAS are then mechanically separated with drum filters, dewatering baskets, centrifuges, belt presses, drain pads, etc. from the sulfurous acid leachate and sent to drying beds. [0050] The separated S0 ₂ treated solids and WAS/RAS are then allowed to chemically dewater on the drying beds to create a Class A disinfected, reduced metal biosolid with less than 10% by weight water with a BTU content comparable to wood. Usually chemical dewatering occurs in 24 hours, but varies based on temperature and humidity.

[0051] The sulfurous acid leachate solution from the dewatered solids may then be adjusted with lime or gypsum to precipitate and remove phosphorous, and metal hydroxides forming a saline adjusted filtrate at a pH suitable for land application or processing in a bioreactor. If dilution by the screened influent also entering the bioreactor is not sufficient to reduce heavy metals or phosphorous concentrations to meet discharge limits, lime or gypsum may be added to increase calcium concentrations where required to overcome sodium salinity effects when reclaimed wastewaters are applied to soils,

[0052] The bioreactor secondary treated waters are then disinfected to provide a tertiary treated wastewater meeting regulatory standards for land application and/or open stream discharge.

[0053] Preferably, the bioreactor secondary treated waters are exposed before land application to oxidizing agents and/or ozone and/or ultraviolet light to create tertiary disinfected waters with reduced PPCPs susceptible to oxidation and ultraviolet inactivation. This may be followed by sulfur dioxide treatment for further reduction of PPCPs susceptible to reducing agents.

[0054] The dewatered disinfected, reduced metal biosolids may then be land applied as Class A biosolids, land filled, or gasified, or burned as they have a BTU/lb value approximating wood chips. [0055] Hydrated or anhydrous lime and/οτ gypsum is used to precipitate heavy metals for removal and add calcium to off-set the sodium salinity of the treated wastewater.

[0056] The pH is of the sulfurous acid in the solids treatment zone is hel d between approximately 1.5 and 4.5, depending upon dwell time required for disinfection. For example, ten minute dwell time is all that is required for disinfection at pH < 2, 1 hour for disinfection at pH < 3.5.

[0057] The wastewater treatment apparatus for wastewater streams and/or conventional wastewater treatment plant process liquid streams containing suspended solids, BOD, COD, nitrogen compounds, phosphorous, and PPCPs comprises:

[0058] a. a filter (clarifier, centrifuge, dewalering strainer, etc. all hereinafter referred to as a 'filter") for removing all or a portion of the suspended solids in wastewater streams and/or conventional wastewater treatment plant process liquid streams forming a liquid steam with sufficient dissolved and suspended solids suitable to support bacteria and microbe bio reduction Of nitrogen, phosphorous, BOD, and other nutrients, and a solids stream,

[0059] b. a transporter (pipes, streams, pumps, auger, etc. all hereinafter referred to as a "transporter") for conveying the separated solids to a solids treatment zone (tank, container, clarifier, equalization tank, etc. all hereinafter referred to as "zone"), and the liquid stream to a bioreactor for bioremediation to remove nitrogen, phosphorous, and nutrients producing secondary treated waters to a degree required to meet wastewater treatment plant discharge requirements. The bioreactor is selected to meet the removal rates required by a discharge permit. These bioreactors as part of the bioremediation process produce different types of waste activated sludge (WAS) and return activated sludge (RAS), hereinafter referred to as WAS/RAS, which are seiit to the solids treatment zone,

[0060] c. a sulfurous acid generator or supply of S0 ₂ is adapted to receive a diverted portion of the liquid stream and inject S0 ₂ into the diverted portion forming a sulfurous acid solution with free SO¾ sulfites and bisulfites suspended, [0061] d. a mixer adding the sulfurous acid solution to the suspended solids and WAS/RAS in the solids treatment zone at a pH and dwell time to:

[0062] i. disinfect and self-agglomerate the suspended solids and WAS/RAS,

[0063] ii. acid leach heavy metals contained in and on the suspended solids and WAS/RAS into solution for subsequent removal and separation, and

[0064] iii. condition the suspended solids and WAS/RAS for subsequent dewatering by shedding water upon separation and drying leaving a sulfurous acid leachate,

[0065] e. a mechanical separator separating the S(¾ treated solids and WAS/RAS from the sulfurous acid leachate,

[0066] f. a liming filtration system adjusting the sulfurous acid leachate solution with lime to precipitate and remove phosphorous, and metal hydroxides forming a saline adjusted filtrate at a pH suitable for land application or processing in a bioreactor,

[0067] g, drying beds where the conditioned suspended solids chemically dewater to create a Class A disinfected, reduced metal biosolid with less than 10% by weight water and a BTU content comparable to wood,

[006S] h. a tank for admixing the saline adjusted filtrate with the secondary treated waters, and

[0069] i. a disinfection system (ozone or UV disinfection systems all hereinafter referred to as "disinfection system-') for disinfecting the saline adjusted filtrate and secondary treated waters to provide a tertiary treated disinfected wastewater without chlorine addition meeting regulatory standards for land application and/or open stream discharge.

[0070] The wastewater treatment apparatus liming filtration system may include filters for removal of heavy metals and phosphorous precipitates.

[0071] Secondary sludge pumping of the RAS/WAS is a part of the treatment plant process apparatus. Return activated sludge (RAS) is continuously pumped back into the secondary biological treatment tank as part of the treatment process. Excess from the settled sludge, which is waste activated sludge (WAS), is pumped to the sludge handling process.

[0072] Usually SO2 is produced on-site with a sulfurous acid generator and injected at a pH held between approximately 1.5 and 4.5, depending upon dwell time required for disinfection. For example, dwell time at pH 2 is 10 minutes; whereas at pH 4.5, it may require a day's storage.

[0073] All or a portion of the suspended solids are removed from the diverted portion of the wastewater streams and/or conventional wastewater treatment plant process liquid streams. The extent of solids removal varies and is dependent upon the type of bioreactor and the type of bacteria and microbes and their temperature sensitivity. Consequently, removal rates may have to be adjusted periodically to leave sufficient dissolved and suspended solids suitable to support bacteria and microbe bio reduction during varying growth periods of the year to meet a wastewater treatment plant's discharge requirements. Usually this is done by a variable flow splitter associated with the wastewater influent, which is adjusted periodically to insure sufficient solids are directed into the bioreactor to sustain microbe and bacteria metabolism.

[0074] The SO? injected solids are then mechanically separated into a solids fraction and a liquid fraction in the drying beds.

[0075] The liquid fraction is then transported back to the bioreactor for bioremediation to remove nitrogen, phosphorous, BOD, and nutrients to the degree required to meet wastewater treatment plant discharge requirements for land application or open stream discharge.

[0076] Preferably the heavy metals in liquid fraction solution are removed via alkalization precipitation, leaving acid leached biosolids meeting Class A biosolids standards upon drying. A recent test of the biosolids treated and separated with the present method at the Montalvo Municipal Improvement District showed fecal coliforms of 187 MPN/gram, dry, with a heating value of 6,932 BTU/lb with 7% moisture by weight. The heavy metals concentrations compared to the Table 3 monthly average §503. 13 standards were:

[0077] Thus, this Montalvo treated biosolids met both the Rule 503 disinfection standards of 1000 MPN, and the heavy metals standards shown above.

[0078] If biosolids disinfection is not sufficient to meet the Class A biosolids standards, the biosolids may be exposed to chemical oxidizing agents, such as peroxide, ozone, Fenton's reagent, chlorine, hypochlorites, etc., heat, ultraviolet light, pasteurization, composting and other disinfection means to further disinfect them.

[0079] Because of the cost, the heavy metals are preferably removed with hydrated or anhydrous lime used to precipitate them as metal hydroxides for removal. This also adds calcium to off-set sodium salts in the liquid fraction, which when added into the bioreactor adjusts salinity and improves SAR soil ratios when land applied.

[0080] Any number of mechanical configurations and devices may be used to implement this mechanical/bioremediation/chemical dewatering treatment method of the suspended solids. These usually involve:

[0081] A. means for diverting all or a portion of wastewater streams and/or conventional wastewater treatment plant process liquid streams entering a bioreactor, such as pumps with filters, splitters, valves, and combinations thereof. Preferably, a variable flow valving system is included to allow different flows to be diverted during the year to insure that sufficient solids enter the bioreactors at different flow rates and temperatures to maintain their bioremediation requirements. [0082] B. tanks of sulfur dioxide, sulfur generators, and other means for injecting S0 ₂ into the diverted portion of wastewater streams and/or conventional wastewater treatment plant process liquid streams are included at a pH and dwell time to generate sufficient sulfurous acid with free SO _2, sulfites and bisulfites to:

[0083] i. disinfect and self-agglomerate the suspended solids,

[0084] ii. acid leach heavy metals contained in and on the suspended solids into solution for subsequent removal and separation, arid

[0085] Hi. condition the suspended solids for subsequent dewatering by shedding water upon separation and drying.

[0086] C. means for removing all or a portion of the suspended solids from the diverted portion of the wastewater streams and/or conventional wastewater treatment plant process liquid streams to reduce the load on bioreactors, but with sufficient dissolved and suspended solids suitable to support bacteria and microbe bioreduction of nitrogen, phosphorous, BOD, and other nutrients, These include, but are not limited to clarifiers, centrifuges, screens, etc.

[0087] D. means for Conveying the liquids to the bioreactor for bioremediation to remove nitrogen, phosphorous, and nutrients to the degree required to meet wastewater treatment plant discharge requirements for land application or open stream discharge, and

[0088] E. means for drying the solids fraction to create a disinfected, reduced metal biosolids with less than 10% by weight water with BTU content comparable to wood, such as drying beds, belt presses, centrifuges, etc,

[0089] Preferably the separated chemically treated solids are land filled, gasified, or burned.

[0090] The preferred means for removal of heavy metals from the chemically treated liquid fraction is via alkalization precipitation to precipitate heavy metals as metal hydroxides and phosphates as calcium and ammonium phosphate for removal. Calcium or potassium hydroxide may be used with the liquid solutions to precipitate heavy metals for removal producing a demetalized chemically treated water for land application or addition to mechanically separated wastewater streams to dilute its heavy metal content. Ammonium hydroxide not only precipitates the metal hydroxides, but adds nitrogen to raise crops if required for land application

[0091] Preferably, the hydrated S0 ₂ is produced on site as needed by passing the inflow streams and/or conventional process liquid streams through a sulfurous acid generator,

[0092] Chemical treatment of biosolids with sulfurous acid reduces pathogens through bisulfite and sulfite kill, while: simultaneously acid leaching heavy metals from the solids into solution for subsequent liming removal. Field tests, such aS those discussed, have shown that this chemical pre-treatment results in biosolids with reduced heavy metals meeting either §503.32(a)(3), (a)(4), (a)(5), (a)(6), (a)(7), or (a)(8) and §503.13 heavy metals standards and having less than 10% water content; thus producing biosolids with BTU content approximating that of wood chips suitable for either land application or burning. Class A pathogen standards are generally met via S0 ₂ addition alone. However^ if further disinfection is required, the type of disinfection method may be supplemented with chemical, heat, ultraviolet, composting, or organic methods.

[0093] An example of a supplemental organic method is vermicomposting as opposed to using traditional composting methods for the management of organic wastes. Vermiprocessing produces a usable product in less time using worms producing worm eastings with greater soil value than aerobic composts. Salmonella, fecal coliform, enteric (intestinal) viruses, and helminthes ova (parasitic worm eggs) are pathogenic organisms present in the sludge composting. While all of these pathogens are present in soils, they can be concentrated in composting and vermicomposting.

[0094] As discussed above, traditional aerobic composting reduces pathogen levels by elevating temperatures between 135-160 degrees F for sufficient time for pathogen destruction to produce Class A compost suitable for use in areas where the public might come in contact with the compost product. Conversely, vermicomposting is managed to ensure temperatures in the organic material remain below 90 degrees F to support high levels of earthworm activity, which many assumed would not kill pathogens,

[0095] The present method thus removes all or a portion of the suspended solids in wastewater streams and/or conventional wastewater treatment plant process liquid streams to expand the capacity of bioreactors by reducing bioreactor loads. It produces Class A biosolids using S0 ₂ for disinfection and self-agglomeration of suspended solids, acid leaching heavy metals contained in and on the suspended solids into solution for subsequent removal and separation, and conditioning the suspended solids for subsequent dewatering by shedding water upon separation and drying. The tertiary treated waters are saline and pH adjusted for land application for open stream discharge. For land application, the tertiary treated waters may also be SAR and pH adjusted for improving local soil conditions to raise different crops.

[0096] DESCRIPTION OF THE DRAWINGS

[0097] Fig. 1 illustrates a proposed wastewater pre-treatment plant diagram for Grants, New Mexico.

[0098] Fig. 2 illustrates new hybrid combination mechanical screening/bioremediation/chemical treatment design

[0099] Fig. 3 illustrates an equipment layout for the design shown in Fig. 2.

[00100] DESCRIPTION OF THE ILLUSTRATED EMBODIMENTS

[00101] An example of the present invention will be best understood by reference to the drawings. The components, as generally described and illustrated, could be arranged and designed in a wide variety of different configurations. Thus, the description of the embodiments is not intended to limit the scope of the invention, as claimed, but is merely representative of presently preferred embodiments of the invention.

[00102] Fig. 1 illustrates a proposed wastewater pre-treatment plant design for Grants, New Mexico using chemical pre-treatment of the entire screened raw sewage. The diagram contemplates new headworks, micro screening, abandonment of the aerated lagoons, and a new BNR nitrogen reduction system to meet and exceed current permitting requirements for land application on an adjacent golf course. The diagram incorporates pre-treatment screening for the entire influent flows to reduce nitrogen, phosphorous, TSS, BOD, and COD loads entering the BNR assuming WTP peak daily flows of 1.8 MGD and average daily flows of 1.5 MGD for wastewater influent having TSS of 250 mg/1 BOD 250 mg/1, TKN 100 mg/1 ammonia of 50 mg/1, fecal conforms > 1600 MPN, and P of 8 mg/1. The effluent design goals are BOD: 10 mg/1, TSS: 10 mg/1, TKN: 10 mg/1, and Total P: 1 mg/i.

[00103] Prc-treating wastewater influent to remove the majority of the TSS also reduces the carbonaceous suspended solids materially reducing both the BOD and COD and some nitrogen. Lime adjustment removes approximately one half of the phosphorous along with the heavy metals and saline balances the salt loads, This also has the effect of reducing the loads on the BNR while adjusting the pH for optimal removal of the remaining nitrogen and phosphorous,

[00104] Chemically pre-treating and disinfecting both the entire influent and the suspended solids to provide disinfected treated waters for use on the adjacent golf course after passing through a BNR produced Class A dewatered biosolids, but used almost a ton of sulfur a day to reduce the pH 7.5 influent to below 3 with sulfurous acid for disinfection. The acidified disinfected wastewater would then have to be raised back to a pH of 6.5 to 7.5 for bioremediation in the BNR, taking a like amount of lime, resulting in O & M cost of $400K/year. Full flow pre-treatment would also require a full influent stream filter, such as the Kason Cross-Flow Dewatering Sieve with a 100 mesh (149 micron) separation capability, or a Westech CleanFlo Shear internally fed rotary drum screen of similar mesh. The high chemical cost for full treatment disinfection and a capital cost of ~$3M for solids screening and liming adjustment of the entire influent was not justifiable where there is a good likelihood of re-infection in the five day BNR nitrogen removal system when compared to the relatively inexpensive ~.5M cost of a Hydoz Wastewater Effluent Ozone post disinfection system with a $25K/year O & M cost.

[00105] A new design using mechanical screening, chemical solids treatment, and bioremediation is therefore required. The solution uses a primary clarifier to separate the solids, which also provides wastewaters, which don't have to be extensively screened before running through a sulfurous acid generator, resulting in a lower capital cost. The liquids leaving the BNR would then be tertiary post-treated with ozone or UV for disinfection to provide a Reuse class IB water for land application On the golf course. This avoids further salt damage to the golf course caused by chlorination.

[00106] A Hydromantis Capdet Works computer model of micro screening and primary clarifier indicates reductions of the BOD and COD loading on the BNR is approximately half. Specifically, this computer model shows that the micro screening and primary clarification reduces TSS from 250 mg/1 to 42 mg/1, BOD from 250 mg/1 to 85 mg/1, TKN from 100 mg/1 to 50 mg/1, phosphorous from 8 mg/1 to 8 mg/1, and ammonia from 50 mg/1 to 25 mg/1.

[00107] Field testing at the Montalvo Municipal Improvement District in California for sulfurous acid waste activated solids treatment shows fecal coliforms reduction from >1600 MPN to <187 MPN meeting Class A standards, and biosolids weight reductions of approximately 37% less than those produced by the conventional drying bed methods.

[00108] Based on the computer modeling and Montalvo biosolids field data, a new hybrid combination mechanical screening/bioremediation/chemical treatment design was developed as shown in Fig. 2 The mass flow assumes 5 gallons of WAS and screened solids per minute are treated in the process with 40 gallons per minute of clear water from the primary clarifier sent through a sulfurous acid generator to acid mix and treat the biosolids in an enclosed tank.

[00109] The equipment layout is shown in Fig. 3. Wastewater raw sewage (RS) influent enters the headworks 1 where major debris is removed via bar screens (not shown). The bar screened influent then enters a micro screen 2, which removes course solids. The micro screened influent then enters a primary clarifier 3» where a splitter 4 sends a portion of the clear water to a sulfurous acid generator for acidification to enter an acid tank 6 for treating separated solids. The remainder of the waters from the primary clarifier 3 is sent to the BNR 1 1 for nitrogen, phosphorous, and BOD reduction. Solids from the primary clarifier are sent to the acid tank % along with WAS from the secondary clarifier 12. The acid treated solids are then separated with a drum separator 8 and sent to a drain pad 13 to complete chemical dewatering. Basic solids from the dewatering box 10 are hauled off for disposal in an appropriate landfill or processing center.

[00110] Liquids from the acid tank 6 are treated with lime from a Lime Feed system 7 to raise the pH > 7 in a Lime Contact Tank 9. These lime treated liquids from the dewatering box 10 are then sent to the BNR 11 for nitrogen, phosphorous and BOD reduction.

100111] Treated liquids from the BNR are then sent to a secondary clarifier 12 to remove the WAS, which is sent to the acid tank 6 for additional acid/lime treatment. The liquids from the secondary clarifier 12 are then sent for tertiary treatment 14 for disinfection, preferably using ozone before being sent to the golf course.

[00112] This new wastewater treatment system provides Class A biosolids with fecal coliforms < 1000 MPN, and a treated effluent < 10 MPN, which is saline and pH adjusted using organic sulfurous acid and lime to improve the soil conditions on the golf course.

[00113] The advantages of this hybrid wastewater pre-treatment design are as follows:

[00114) 1. Reduces loads on the BNR expanding its capacity with N< 10 mg/1, P<1 mg/1, and tertiary waters < 10 MPN.

[00115] 2. Produces a drier odorless solids resulting in 37% weight haulage savings.

[00116] 3. No anaerobic digestion costs and associated H ₂ S production.

[00117] 4. Disinfected Class A biosolid (<187 MPN and reduced heavy metals), for use on the adjacent golf course— no landfill costs.

[00118] 5. Slightly acidic biosolid (pH -4.6) suitable for alkaline soils.

[00119] 6. Periodic separate disposal of heavy metals and phosphates.

[00120] 7. As a new biosolids treatment technology, it may qualify for special grant funding. [00121] 8. O & M costs of approximately $100K/year for solids treatment and tertiary disinfection.

[00122] The impact of reduced suspended solids on bioreactor processing capacity is dependent upon their carbonaceous content. Carbonaceous suspended solids materially impact BOD and COD. As a rule of thumb BOD comprises 40-60 of the TSS, according to Kemira,

As the cost for

carbonaceous suspended solids removal is considerably less than installing additional bioreactor capacity, by implementing suspended solids removal first improves bioremediation.

[00123] The wastewater treatment apparatus may include a controller associated with the liming filtration system, which comprises a lime supply tank and a gypsum supply tank These tanks are selectively activated by the controller to adjust the pH of the sulfurous acid leachate solution by adding lime where the pH is to be elevated, or gypsum where the pH is to remain approximately the same. Both add calcium to adjust the sodium/calcium ratio of the saline SAR adjusted filtrate. The sulfates from the reduced sulfurous acid off-sets chlorides in the wastewater. In this way the tertiary treated saline wastewater is periodically adjusted for land application soil conditions.

[00124] Usually the liming filtration system includes filters and storage for periodic removal of heavy metals and phosphorous precipitates that gradually accumulate relative to the separated acid treated suspended solids and WAS/RAS.

[00125] Preferably, the disinfection system comprises an ozonation system to not only disinfect, but reduce PPCPs susceptible to oxidation. A second sulfurous acid generator may then be included to adjust the acidity of the tertiary ozone treated wastewater to further reduce PPCPs susceptible to reduction.

[00126] The above mechanical/biological/chem ical wastewater treatment method and apparatus employs organic sulfurous acid and lime injected into wastewater inflow streams and/or conventional process liquid streams containing suspended solids, pathogens, PPCPs, ammonia, phosphorous, BOD, and COD at a pH and dwell time to:

[00127] a. generate sufficient sulfurous acid with free SQ ₂ , sulfites and bisulfites to disinfect and self-agglomerate the suspended solids,

[00128] b. acid leach heavy metals contained in and on the suspended solids into solution for subsequent separations

[00129] c. reduce loading on bioreactors reducing nitrogen, BOD, COD, and phosphorous,

[00130] d, condition the suspended solids for subsequent chemical dewatering shedding water upon separation and drying forming a Class A biosolid with less man 10% by weight water content and

[00131] e. create custom designed recovered wastewater suitable for land application or open stream discharge.

[00132] The present invention may be embodied in other specific forms without departing from its structures, methods, or other essential characteristics as broadly described herein arid claimed hereinafter. The described embodiments are to be considered in all respects only as illustrative, and not restrictive. The scope of the invention is, therefore, indicated by the appended claims, rather than by the foregoing description. AH changes that come within the meaning and range of equivalency of the claims are to be embraced within their scope.