METHOD AND APPARATUS TO INCREASE WASTEWATER BIOREACTOR PROCESSING CAPACITY WHILE REDUCING GREENHOUSE GAS EMISSIONS

Abstract

A wastewater treatment method and apparatus separating suspended solids in influent wastewater streams, and injecting SO.sub.2 or sulfurous acid into the suspended solids at a pH and dwell time to generate sufficient sulfurous acid with free SO.sub.2, sulfites and bisulfites to self-agglomerate the suspended solids, acid leach heavy metals contained in and on the suspended solids into solution for subsequent separation, condition the suspended solids for chemical dewatering producing a dried biofuel biosolid with less than 10% by weight water and a BTU content between 6,000 and 9,000 BTU/lb., and gasifying or combusting the dried acid treated suspended solids to produce power or energy with reduced greenhouse gas emissions.

Claims

1. A wastewater treatment method for wastewater streams and/or wastewater treatment plant process liquid streams containing suspended negatively charged colloidal solids in solution comprising: a. removing all or a portion of the solids from solution, b. adding SO.sub.2 or sulfurous acid with free SO.sub.2, sulfites and bisulfites to the removed solids at a pH and dwell time to: i. self-agglomerate the solids, ii. acid leach heavy metals contained in and on the solids into the solution for subsequent removal and separation, and iii. condition the suspended solids to dewater; c. separating the SO.sub.2 or sulfurous acid treated solids allowing them to dry to create a biosolid with less than 10% by weight water and a BTU content between 6,000 and 9,000 BTU/lb., and d. gasifying or combusting the dried acid treated suspended solids to produce power or energy with greenhouse gas emissions less than emitted by landfilling and/or anaerobic digestion.

2. The wastewater treatment method according to claim 1, including transferring the solution with reduced solids and BOD to a bioreactor for bioremediation to remove remaining nitrogen, phosphorous, and nutrients to the degree required to meet wastewater treatment plant discharge requirements.

3. The wastewater treatment method according to claim 1, wherein the heavy metals in solution are removed via alkalization precipitation and filtration removal.

4. The wastewater treatment method according to claim 3, wherein hydrated or anhydrous lime is used to precipitate heavy metals for removal.

5. A wastewater treatment apparatus for wastewater streams and/or wastewater treatment plant process liquid streams containing suspended negatively charged colloidal solids in solution comprising: a. means for removing all or a portion of the solids from solution, b. means for adding SO.sub.2 or sulfurous acid with free SO.sub.2, sulfites and bisulfites to the removed solids at a pH and dwell time to: i. self-agglomerate the solids, ii. acid leach heavy metals contained in and on the solids into the solution for subsequent removal and separation, and iii. condition the suspended solids to dewater; c. means for separating the sulfurous acid treated solids allowing them to dry to create a biosolid with less than 10% by weight water and a BTU content between 6,000 and 9,000 BTU/lb., and d. means for gasifying or combusting the dried acid treated suspended solids to produce power or energy with reduced greenhouse gas emissions less than emitted by landfilling and/or anaerobic digestion.

6. The wastewater treatment apparatus according to claim 5, wherein the means for gasifying comprises a gasifier or plasma gasifier, and the means for combustion comprises a co-fired boiler or kiln.

7. The wastewater treatment apparatus according to claim 5, including alkalization means of the heavy metals in solution, and filtration means for removal of heavy metals precipitate and phosphates.

8. The wastewater treatment apparatus according to claim 7, wherein the alkalization means comprises liming equipment to precipitate heavy metals for removal.

5. wastewater treatment apparatus according to claim 5, wherein the means for adding sulfurous acid comprises a sulfurous acid generator combusting raw sulfur producing SO.sub.2 for injection into the wastewater and/or separated solids.

Description

DESCRIPTION OF THE DRAWINGS

[0052] FIG. 1 illustrates the source of greenhouse gas emissions for a typical wastewater treatment plant.

[0053] FIG. 2 illustrates the percentages of greenhouse gas emissions from various wastewater treatment plant processes.

[0054] FIG. 3 illustrates how suspended solids substrates adsorb PPCPs, pathogens, heavy metals, which are released when the substrate is broken down by microbes.

[0055] FIG. 4 illustrates salt balancing with bi-valent ions to repeal and leach away from the roots monovalent salts, retaining needed plant nutrients.

[0056] FIG. 5 illustrates the fuel value of anaerobically digested sludge vs. separated primary solids.

[0057] FIG. 6 illustrates acid cation agglomeration of colloidal biosolids without polymers.

[0058] FIG. 7 illustrates separated biosolids drying energy usage for polymer separated sludges vs. chemically dried separated solids.

[0059] FIG. 8 illustrates an example of a flow diagram removing upfront suspended solids for chemical drying, and conditioning the filtrate as reclaimed water for land application or further processing.

[0060] The patent or application file contains at least one drawing executed in color. Copies of this patent or patent application publication with color drawing(s) will be provided by the Office upon request and payment of the necessary fee.

DESCRIPTION OF THE ILLUSTRATED EMBODIMENTS

[0061] 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.

[0062] FIG. 1 illustrates the source of greenhouse gas emissions for a typical wastewater treatment plant.

[0063] FIG. 2 illustrates the percentages of greenhouse gas emissions from various wastewater treatment plant processes illustrated in FIG. 1. Land application produces 37% of the greenhouse gas emissions followed by anaerobic digestion producing 35% of the greenhouse gas emissions. Gasification/combustion of the upfront separated suspended solids avoids both these processes to significantly reduce greenhouse gas production while generating power.

[0064] For example, anaerobic digestion is used to reduce sludge disposal volume to at best 50%. The process generates low BTU biogas releasing methane and CO.sub.2 greenhouse gases, if not captured. Presently 600 wastewater treatment plants in the US flare off this biogas directly to atmosphere, losing any fuel benefit and compounding greenhouse gas emissions. More importantly, this process still requires landfilling of the balance of the sludge resulting in a large footprint as biological processes are slow to degrade these remaining sludges.

[0065] Land application decomposition produces CO.sub.2, H.sub.2S, SOx, NOx, and H.sub.2O greenhouse gas emissions. It also requires solids drying to reduce the disposal volume and has a long decomposition time in years, continually emitting greenhouse gases to atmosphere, while generating odors.

[0066] FIG. 3 illustrates how suspended solids substrates adsorb PPCPs, pathogens, heavy metals, which are released when the substrate is broken down by microbes. Their upfront removal significantly improves reclaimed water quality and reduces loading on a wastewater treatment plant's bioremediation equipment; thereby expanding its processing capacity. Gasification/Combustion of the separated solids then destroys the sorbed PPCPs, prions, pathogens. Heavy metals are separately acid washed from the solids substrate for chemical precipitation via lime addition to precipitate metal hydroxides for independent disposal.

[0067] FIG. 4 illustrates salt balancing with bi-valent ions to repeal and leach away from the roots monovalent salts, retaining needed plant nutrients.

[0068] FIG. 5 illustrates the fuel value of anaerobically digested sludge vs. separated primary solids. Separated primary solids have 25% more fuel value than anaerobically digested sludge as the anaerobic microorganisms first consume the high energy volatiles to produce biogas. Thus the fuel value of primary separated solids is approximately 9,000 BTU/lb. compared to waste activated separated sludge having a BTU value of approximately 6,500 BTU/lb.

[0069] FIG. 6 illustrates acid cation agglomeration of colloidal biosolids without polymers. Suspended solids are negatively charged, and when cation acid is added, they readily coagulate for easy separation. As the acid addition avoids hydrophilic polymers, the sulfurous acid chemically dried biosolids contain less than 10% water vs. 40% water of polymer separated solids.

[0070] FIG. 7 illustrates separated biosolids drying energy usage for polymer separated sludges vs. chemically dried separated solids. For gasification or combustion, the separated biosolids must be dried to less than 20% water content before power generation. This requires large drying energy usage of polymer separated solids, which constitutes approximately 60% of the fuel value according to Techno-Economic Analysis of Wastewater Biosolids Gasification by Nick Lumley et al; ww3.aiche.org/...?p325428.p..., supra. Chemically dried separated solids thus generates significantly more fuel value than dried polymer separated fuels.

[0071] FIG. 8 illustrates an example of a flow diagram removing upfront suspended solids for chemical drying, and conditioning the filtrate as reclaimed water for land application or further bioremediation processing. The saline wastewater is filtered using centrifuges, clarifiers, or mechanical filters removing the suspended solids with sorbed PPCPs/Prions/Pathogens for transfer to a mixing tank. Sulfurous acid at a pH less than 6.5 is then added and held for approximately 10 minutes The slurried acidified separated solids is then transferred to a drain Pad/Dryer, belt press, etc. for chemical drying without heat. After 24 to 48 hours, the chemically dried solids have less than 10% water and are transferred to a gasifier or combuster, such as a kiln, co-fired boiler, etc. This destroys sorbed PPCPs/Prions/Pathogens, while generating more power output with reduced greenhouse gases, as methane and nitrous oxide anaerobic production are avoided.

[0072] The filtrate is then lime adjusted in a dwell tank at a pH greater than or equal to 9 for precipitating metal hydroxides, calcium phosphates, and calcium carbonates for separation with a filter or settling tank. The second filtrate is then pH adjusted with sulfurous acid, producing a reclaimed wastewater which is metal free, salt balanced, and has reduced PPCPs/Prions/Pathogens and reduced N and P. It may be land applied or further bioremediated with loading reduced 40%.

[0073] Upfront TSS removal before biological reduction significantly increases the capacity of the wastewater treatment plant to reduce BOD, nitrogen, and greenhouse gas production. It also provides a renewable biofuel for co-firing with other fuels to reduce overall greenhouse gas production, particularly when co-fired with coal significantly reducing NOx and SOx production.

[0074] The present invention may be embodied in other specific forms without departing from its structures, methods, or other essential characteristics as broadly described herein and 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. All changes that come within the meaning and range of equivalency of the claims are to be embraced within their scope.