WO2010089735A1 - Methods and systems for gaseous emission reduction from sewage management systems - Google Patents

Abstract

A method for reducing gaseous emission from a sewage management system including removing at least 20% of a solid biomass portion of a sewage suspension, which flows within the sewage management system, thereby reducing the gaseous emission.

Description

METHODS AND SYSTEMS FOR GASEOUS EMISSION REDUCTION FROM SEWAGE MANAGEMENT SYSTEMS

REFERENCE TO CO-PENDING APPLICATIONS

Applicant hereby claims priority of U. S. Provisional Patent Application Serial No. 61/150,007, filed on February 5, 2009, entitled "Methods and Systems for Gaseous Emission Reduction from Sewage Management Systems", incorporated herein by reference.

FIELD OF THE INVENTION

The present invention relates generally to methods and systems for reducing gaseous emission from sewage management systems and more specifically relates to methods and systems for reduction of carbon dioxide, methane, sulfur dioxide and nitrogen oxide emission from sewage management systems.

BACKGROUND

Carbon dioxide, one of the greenhouse gases, is produced during the combustion of fossil fuels, especially coal, in furnaces and power plants. Recent scientific studies have shown that emissions of carbon dioxide and other greenhouse gases, such as methane, sulfur dioxide, and nitrogen oxides, can have a significant effect on climate change. The prospect of climate change caused, at least in part, by emission of carbon dioxide and other greenhouse gases has led to international concern and to international treaties, such as the Kyoto Protocol.

The Kyoto Protocol specifies that the industrialized nations of the world are to significantly reduce carbon dioxide emissions. In addition to that requirement, the Kyoto Protocol allows "emission trading," under which countries with higher emission levels of greenhouse gases can buy "emission credits" from countries that are not emitting their allotted levels of greenhouse gases. The reduced gaseous emission is generally presented in Certified Emission Reduction (CER) units. CER is generally defined as a ton of carbon credits, which is an allowance for permitting an emission of a ton of carbon dioxide within a carbon credit system.

SUMMARY OF THE INVENTION

There is thus provided in accordance with an embodiment of the present invention a method for reducing gaseous emission from a sewage management system including removing at least 20% of a solid biomass portion of a sewage suspension, which flows within the sewage management system, thereby reducing the gaseous emission.

There is thus provided in accordance with another embodiment of the present invention a method for reducing gaseous emission from a sewage management system including removing at least 20% of a Total Suspended Solid (TSS) portion of a sewage suspension, which flows within the sewage management system, thereby reducing the gaseous emission.

There is thus provided in accordance with yet another embodiment of the present invention a method for reducing gaseous emission from a sewage management system including removing a solid biomass portion of a sewage suspension, which flows within the sewage management system, thereby reducing any one of the following: a carbon content of the sewage suspension by approximately 10% - 90%, an organic matter content of the sewage suspension by approximately 5% - 95%, a cellulose content of the sewage suspension by approximately 20% - 95%, a Biological Oxygen Demand or Biochemical Oxygen Demand (BOD) of the sewage suspension by approximately 10% - 90%, a Total Solid (TS) content of the sewage suspension by approximately 5% - 90%, and a Total Suspended Solid (TSS) content of the sewage suspension by approximately 10% - 90%, thereby reducing the gaseous emission.

In accordance with an embodiment of the invention the removal of at least emission. Additionally, reducing the gaseous emission includes at least one of the following: reduction of methane emission during anaerobic processing of the sewage suspension within the sewage management system following the removal of the solid biomass portion therefrom, reduction of methane emission during landfilling of sludge produced by processing of the sewage suspension within the sewage management system following the removal of the solid biomass portion therefrom, and reduction of carbon dioxide emission due to reduced electricity consumption during operation of the sewage management system. Accordingly, the removed solid biomass portion is processed so as to produce a combustion product for replacing fossil foils, thereby further reducing gaseous emission caused by combustion of fossil foils.

In accordance with another embodiment of the invention the gaseous emission includes a methane emission and a carbon dioxide emission. Additionally, the gaseous emission includes a methane emission, a carbon dioxide emission, a sulfur dioxide emission and a nitrogen oxide emission. Accordingly, Certified Emission Reduction (CER) units are earned by the reduction of the gaseous emission. Furthermore, the sewage management system is a Wastewater Treatment Plant.

There is thus provided in accordance with an embodiment of the present invention a system for reducing gaseous emission from a sewage management system including a solid biomass removal system operative to remove at least 20% of a solid biomass portion of a sewage suspension, which flows within the sewage management system, thereby reducing the gaseous emission.

There is thus provided in accordance with another embodiment of the present invention a system for reducing gaseous emission from a sewage management system including a solid biomass removal system operative to remove at least 20% of a Total Suspended Solid (TSS) portion of a sewage suspension, which flows within the sewage management system, thereby reducing the gaseous emission.

There is thus provided in accordance with yet another embodiment of the present invention a system for reducing gaseous emission from a sewage management system including a solid biomass removal system operative to remove a solid biomass portion of a sewage suspension, which flows within the sewage management system, thereby reducing any one of the following: a carbon content of the sewage suspension by approximately 10% - 90%, an organic matter content of the sewage suspension by approximately 5% - 95%, a cellulose content of the sewage suspension by approximately 20% - 95%, a Biological Oxygen Demand or Biochemical Oxygen Demand (BOD) of the sewage suspension by approximately 10% - 90%, a Total Solid (TS) content of the sewage suspension by approximately 5% - 90%, and a Total Suspended Solid (TSS) content of the sewage suspension by approximately 10% - 90%, thereby reducing the gaseous emission.

In accordance with an embodiment of the invention removal of at least 20% of the solid biomass portion results in a reduction of at least 20% of the gaseous emission. Accordingly, reducing the gaseous emission includes at least one of the following: reduction of methane emission during anaerobic processing of the sewage suspension within the sewage management system following the removal of the solid biomass portion therefrom, reduction of methane emission during landfilling of sludge produced by processing of the sewage suspension within the sewage management system following the removal of the solid biomass portion therefrom, and reduction of carbon dioxide emission due to reduced electricity consumption during operation of the sewage management system. Additionally, removed solid biomass portion is processed in a solid biomass processing system so as to produce a combustion product for replacing fossil foils, thereby further reducing gaseous emission caused by combustion of fossil foils.

In accordance with another embodiment of the invention the gaseous emission includes a methane emission and a carbon dioxide emission. Additionally, the gaseous emission includes a methane emission, a carbon dioxide emission, a sulfur dioxide emission and a nitrogen oxide emission. Accordingly, Certified Emission Reduction (CER) units are earned by the reduction of the gaseous emission. Furthermore, the sewage management system is a Wastewater Treatment Plant.

BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a simplified block diagram of a system for gaseous emission reduction from sewage management systems, constructed and operative in accordance with an embodiment of the present invention;

Fig. 2 is a graph of some sewage composition components prior to processing the sewage in the system of Fig. 1 Vs. the resulting composition components following processing in the system of Fig.1;

Fig. 3 is a simplified block diagram of a system for reducing gaseous emission caused by combustion of fossil fuels, by utilizing elements of the system of Fig. i;

Fig. 4 is a graph of Certified Emission Reduction (CER) units per year gained by use of the systems of Figs. 1 and 3 in a large scale WWTP; and

Fig. 5 is a graph of CER units per year gained by use of the systems of Figs. 1 and 3 in a small scale WWTP.

DETAILED DESCRIPTION

In the following description, various aspects of the present invention will be described. For purposes of explanation, specific configurations and details are set forth in order to provide a thorough understanding of the present invention. However, it will also be apparent to one skilled in the art that the present invention may be practiced without the specific details presented herein. Furthermore, well known features may be omitted or simplified in order not to obscure the present invention.

Reference is now made to Fig. 1, which is a simplified block diagram of a system for gaseous emission reduction from sewage management systems, constructed and operative in accordance with an embodiment of the present invention. As seen in Fig. 1, sewage 10 may be introduced into a solid biomass removal system 20.

Sewage 10 may be raw sewage, i.e. a sewage stream flowing within a sewerage waste system prior to standard wastewater treatment thereof. Raw sewage may flow from a municipal sewage waste system or any other sewerage system, such as, for example, domestic, industrial or agricultural waste systems. The municipal sewage waste system may include residential, commercial, and industrial waste discharges and stormwater runoff.

Raw sewage of the municipal sewage waste system is a suspension comprising approximately a 25 - 99.99% liquid portion and approximately a 0.01 - 75% solid portion. Typically, the municipal sewage waste system is a suspension comprising approximately a 75 - 99.99% liquid portion and approximately a 0.01 - 25% solid portion. The solid portion is partially suspended within the liquid portion and partially solved therein. Typically, the liquid portion comprises water and oils. The solid portion includes sand, non-organic matter, plastic particles, organic matter, organic fibers comprising cellulose fibers and other sewage refuse. The solid portion of raw sewage is an aggregate of particles containing generally up to 15% sand, 15% minerals, 20 - 90% cellulose fibers, 10 - 20% hemicellulose and 3 - 10% lignin. The solid portion also includes oil and water adsorbed to the particles. Typically, the solid portion of raw sewage includes 0.5 - 25% of oil therein.

Alternatively, sewage 10 may also be treated sewage, treated by standard wastewater treatment thereof and may be eflused into solid biomass removal system 20 from a municipal sewage waste system, a WWTP or any location within the WWTP prior to digestion of the sewage therein.

Sewage 10 may flow into solid biomass removal system 20 via a pipe or by any other suitable means.

Solid biomass removal system 20 is operative to remove solid biomass from sewage 10 by any suitable means. For example, solid biomass may be removed from sewage 10 by a method for removal of a solid portion from sewage disclosed in applicant's PCT patent applications PCT/US2008/009679 and PCT/US2009/33802, which are hereby incorporated by reference.

Additionally, solid biomass may be removed by employing Dissolved Air Floation (DAF) technology. DAF technology is a process for removal of suspended matter from a suspension. The removal is achieved by dissolving a gas, typically air, in the suspension under pressure and then releasing the gas at atmospheric pressure in a flotation tank or basin. The released gas forms small bubbles which adhere to the suspended matter causing the suspended matter to float to the surface of the suspension. The floating suspended matter is thereafter removed from the surface. Thus suspended solid biomass may be removed from the sewage suspension within the solid biomass removal system 20.

Alternatively the solid biomass may be removed by introducing sewage 10 into a solid particle entrapping device, which may be comprised of a single net or a multiplicity of nettings for entrapping the solid biomass portion of sewage 10. The multiplicity of nettings may be a series of nettings wherein each subsequent netting is formed with apertures of a smaller size than the previous netting so as to provide additional trapping of solid biomass particles from the sewage 10. A netting mesh may be substantially in the range of 5 - 400 microns, for example.

The nettings may be formed in any suitable configuration and may be formed of any suitable material such as a corrosive resistive material and/or a high pressure resistive material, typically aluminum, for example.

It is appreciated that removal of solid biomass from sewage 10 may be achieved in any suitable manner, such as by separation by conveyor belts formed of conveyor belt mesh; centrifiigation, such as flow centrifugation or hydrocyclonic centrifugation, for example; separation by screw presses; filtering by disk filters, filter presses, media filters, such as filters containing fibers, for example, biological filters, such as filters containing cellulose, for example, chemical filters, such as filters containing silica, for example, a filter employing backflushing technology, or any other suitable method for removing solid biomass from sewage 10.

A backflushing filter may be commercially available from the Salsnes Filter AS company of 279 Postboks, Namsos 7801, Norway, under the catalogue number of SF 6000. A backflushing filter comprises a screen or a filtration media operative to filter solids such that solids accumulate on a first surface of the screen or filtration media. Liquid, generally water, is introduced to flow from an opposite surface of the screen or filtration media to the first surface thereof. This reverse flow of liquid through the screen or filtration media is used for removing solids accumulated on the screen or filtration media during the filtration process. Thus solid biomass may be removed from the sewage 10 within the solid biomass removal system 20.

In accordance with an embodiment of the present invention approximately more than 20% of the solid biomass portion of sewage 10 may be removed by the solid biomass removal system 20. In accordance with another embodiment of the present invention a range of approximately 20 - 30% of the solid biomass portion of sewage 10 may be removed by the solid biomass removal system 20. In accordance with yet another embodiment of the present invention a range of approximately 30 - 40% of the solid biomass portion of sewage 10 may be removed by the solid biomass removal system 20. In accordance with still another embodiment of the present invention a range of approximately 40 - 50% of the solid biomass portion of sewage 10 may be removed by the solid biomass removal system 20. In accordance with another embodiment of the present invention a range of approximately 50 - 60% of the solid biomass portion of sewage 10 may be removed by the solid biomass removal system 20. In accordance with yet another embodiment of the present invention a range of approximately 60 - 70% of the solid biomass portion of sewage 10 may be removed by the solid biomass removal system 20. In accordance with still another embodiment of the present invention a range of approximately 70 - 80% of the solid biomass portion of sewage 10 may be removed by the solid biomass removal system 20. In accordance with another embodiment of the present invention a range of approximately 80 - 90% of the solid biomass portion of sewage 10 may be removed by the solid biomass removal system 20. In accordance with another embodiment of the present invention more than approximately 90% of the solid biomass portion of sewage 10 may be removed by the solid biomass removal system 20.

A substantially solid biomass portion 30 removed from the solid biomass removal system 20 is comprised of solid particles and liquids adsorbed to the solid particles, such as oil and water. The solid biomass portion 30 mainly includes organic matter such as cellulose, though inorganic matter may also adhere thereto.

A residual substantially liquid portion 40 is discharged from solid biomass removal system 20. Residual portion 40 comprises a smaller amount of solid biomass than sewage 10, following the removal of solid biomass portion 30 by the solid biomass removal system 20. An example showing some sewage composition components prior to removal of the solid biomass and following removal of the solid biomass within solid biomass removal system 20 is shown in Fig. 2 and will be described in detail hereinbelow.

Residual portion 40 may be discarded or may flow to a sewage management system 50, such as back to the municipal sewage waste system, a WWTP or any location prior to digestion within the WWTP, in any suitable manner, such as by conduits. The residual portion 40 may be treated within the sewage management system 50 by any conventional wastewater treatment methods.

It is well known in the art that gas, such as greenhouse gases, typically carbon dioxide and/or methane, are emitted during conventional treatment within sewage management system 50, typically a WWTP. Sewage management systems 50 that have a sewage stream introduced therein, without removal of the solid biomass portion 30 within the solid biomass removal system 20, emit carbon dioxide and/or methane during conventional treatment as follows: (1) the solid biomass portion of sewage 10 is introduced into the sewage management system 50 to be anaerobically aerated and digested into sludge. Greenhouse gases, mainly methane, are emitted during the anaerobic digestion of the solid biomass portion; (2) greenhouse gases, mainly carbon dioxide, are emitted due to conventional electricity consumption caused by operation of the sewage management system 50; and (3) greenhouse gases, mainly methane, are emitted from landfilled sludge.

It is a thus appreciated that removal of solid biomass portion 30 by use of the solid biomass removal system 20 allows for reducing the gaseous emission from sewage management system 50. This is due to the substantially reduced volume of solid biomass entering the sewage management system 50 following removal of solid biomass by solid biomass removal system 20. Subsequently, gaseous emission during anaerobic processing within the sewage management system 50 is substantially reduced. Additionally, the electrical consumption due to operation of the sewage management system 50 is reduced thus allowing for reduction of gaseous emission therefrom. Moreover, gaseous emission from landfilled sludge is substantially reduced due to the reduced volume of landfilled sludge. It is appreciated that removal of at least 20% of the solid biomass portion results in a reduction of at least 20% of the gaseous emission. Examples 1-5 hereinbelow show that reduced methane and carbon dioxide emission from a conventional WWTP was achieved due to removal of solid biomass by the biomass removal system 20.

The removed solid biomass portion 30 may be introduced into a solid biomass processing system 60, for further processing thereof, as will be described hereinbelow with reference to Fig. 3.

Removal of the solid biomass portion 30 by biomass removal system 20 reduces various components and parameters of the sewage composition, thus allowing reduction of gaseous emission from the sewage composition processed within a sewage management system 50. For example, the carbon content of the sewage 10 may be reduced by approximately 10% - 90%; the organic matter content of the sewage 10 may be reduced by approximately 5% - 95%; the cellulose content of the sewage 10 may be reduced by approximately 20% - 95%; the Biological Oxygen Demand or Biochemical Oxygen Demand (BOD) of the sewage 10 may be reduced by approximately 10% - 90%; the Total Solids (TS) of the sewage 10 may be reduced by approximately 5% - 90%; and the Total Suspended Solids (TSS) of the sewage 10 may be reduced by approximately 10% - 90%.

In accordance with an embodiment of the present invention a range of approximately 10 - 20% of the carbon content of sewage 10 may be removed by the solid biomass removal system 20. In accordance with another embodiment of the present invention a range of approximately 20 - 30% of the carbon content of sewage 10 may be removed by the solid biomass removal system 20. In accordance with yet another embodiment of the present invention a range of approximately 30 - 40% of the carbon content of sewage 10 may be removed by the solid biomass removal system 20. In accordance with still another embodiment of the present invention a range of approximately 40 - 50% of the carbon content of sewage 10 may be removed by the solid biomass removal system 20. In accordance with another embodiment of the present invention a range of approximately 50 - 60% of the carbon content of sewage 10 may be removed by the solid biomass removal system 20. In accordance with yet another embodiment of the present invention a range of approximately 60 - 70% of the carbon content of sewage 10 may be removed by the solid biomass removal system 20. In accordance with still another embodiment of the present invention a range of approximately 70 - 80% of the carbon content of sewage 10 may be removed by the solid biomass removal system 20. In accordance with another embodiment of the present invention a range of approximately 80 - 90% of the carbon content of sewage 10 may be removed by the solid biomass removal system 20. In accordance with another embodiment of the present invention more than approximately 90% of the carbon content of sewage 10 may be removed by the solid biomass removal system 20.

In accordance with an embodiment of the present invention approximately more than 5% of the organic matter content of sewage 10 may be removed by the solid biomass removal system 20. In accordance with another embodiment of the present invention a range of approximately 20 - 30% of the organic matter content of sewage 10 may be removed by the solid biomass removal system 20. In accordance with yet another embodiment of the present invention a range of approximately 30 - 40% of the organic matter content of sewage 10 may be removed by the solid biomass removal system 20. In accordance with still another embodiment of the present invention a range of approximately 40 - 50% of the organic matter content of sewage 10 may be removed by the solid biomass removal system 20. In accordance with another embodiment of the present invention a range of approximately 50 - 60% of the organic matter content of sewage 10 may be removed by the solid biomass removal system 20. In accordance with yet another embodiment of the present invention a range of approximately 60 - 70% of the organic matter content of sewage 10 may be removed by the solid biomass removal system 20. In accordance with still another embodiment of the present invention a range of approximately 70 - 80% of the organic matter content of sewage 10 may be removed by the solid biomass removal system 20. In accordance with another embodiment of the present invention a range of approximately 80 - 90% of the organic matter content of sewage 10 may be removed by the solid biomass removal system 20. In accordance with another embodiment of the present invention approximately 90 - 95% of the organic matter content of sewage 10 may be removed by the solid biomass removal system 20. In accordance with another embodiment of the present invention more than approximately 95% of the organic matter content of sewage 10 may be removed by the solid biomass removal system 20.

In accordance with an embodiment of the present invention a range of approximately 20 - 30% of the cellulose content of sewage 10 may be removed by the solid biomass removal system 20. In accordance with yet another embodiment of the present invention a range of approximately 30 - 40% of the cellulose content of sewage 10 may be removed by the solid biomass removal system 20. In accordance with still another embodiment of the present invention a range of approximately 40 - 50% of the cellulose content of sewage 10 may be removed by the solid biomass removal system 20. In accordance with another embodiment of the present invention a range of approximately 50 - 60% of the cellulose content of sewage 10 may be removed by the solid biomass removal system 20. In accordance with yet another embodiment of the present invention a range of approximately 60 - 70% of the cellulose content of sewage 10 may be removed by the solid biomass removal system 20. In accordance with still another embodiment of the present invention a range of approximately 70 - 80% of the cellulose content of sewage 10 may be removed by the solid biomass removal system 20. In accordance with another embodiment of the present invention a range of approximately 80 - 90% of the cellulose content of sewage 10 may be removed by the solid biomass removal system 20. In accordance with another embodiment of the present invention approximately 90 - 95% of the cellulose content of sewage 10 may be removed by the solid biomass removal system 20. In accordance with another embodiment of the present invention more than approximately 95% of the cellulose content of sewage 10 may be removed by the solid biomass removal system 20.

In accordance with an embodiment of the present invention a range of approximately 10 - 20% of the BOD of sewage 10 may be removed by the solid biomass removal system 20. In accordance with another embodiment of the present invention a range of approximately 20 - 30% of the BOD of sewage 10 may be removed by the solid biomass removal system 20. In accordance with yet another embodiment of the present invention a range of approximately 30 - 40% of the BOD of sewage 10 may be removed by the solid biomass removal system 20. In accordance with still another embodiment of the present invention a range of approximately 40 - 50% of the BOD of sewage 10 may be removed by the solid biomass removal system 20. In accordance with another embodiment of the present invention a range of approximately 50 - 60% of the BOD of sewage 10 may be removed by the solid biomass removal system 20. In accordance with yet another embodiment of the present invention a range of approximately 60 - 70% of the BOD of sewage 10 may be removed by the solid biomass removal system 20. In accordance with still another embodiment of the present invention a range of approximately 70 - 80% of the BOD of sewage 10 may be removed by the solid biomass removal system 20. In accordance with another embodiment of the present invention a range of approximately 80 - 90% of the BOD of sewage 10 may be removed by the solid biomass removal system 20. In accordance with another embodiment of the present invention more than approximately 90% of the BOD of sewage 10 may be removed by the solid biomass removal system 20.

It is noted that the BOD is generally defined as a measure of the capacity of water to consume oxygen during the decomposition of organic matter. The BOD is used to quantitate the degree of sewage refuse pollutants, such as solid biomass, within sewage.

In accordance with an embodiment of the present invention a range of approximately 5 - 20% of the TS of sewage 10 may be removed by the solid biomass removal system 20. In accordance with another embodiment of the present invention a range of approximately 20 - 30% of the TS of sewage 10 may be removed by the solid biomass removal system 20. In accordance with yet another embodiment of the present invention a range of approximately 30 - 40% of the TS of sewage 10 may be removed by the solid biomass removal system 20. In accordance with still another embodiment of the present invention a range of approximately 40 - 50% of the TS of sewage 10 may be removed by the solid biomass removal system 20. In accordance with another embodiment of the present invention a range of approximately 50 - 60% of the TS of sewage 10 may be removed by the solid biomass removal system 20. In accordance with yet another embodiment of the present invention a range of approximately 60 - 70% of the TS of sewage 10 may be removed by the solid biomass removal system 20. In accordance with still another embodiment of the present invention a range of approximately 70 - 80% of the TS of sewage 10 may be removed by the solid biomass removal system 20. In accordance with another embodiment of the present invention a range of approximately 80 - 90% of the TS of sewage 10 may be removed by the solid biomass removal system 20. In accordance with another embodiment of the present invention more than approximately 90% of the TS of sewage 10 may be removed by the solid biomass removal system 20.

In accordance with an embodiment of the present invention a range of approximately 10 - 20% of the TSS of sewage 10 may be removed by the solid biomass removal system 20. In accordance with another embodiment of the present invention a range of approximately 20 - 30% of the TSS of sewage 10 may be removed by the solid biomass removal system 20. In accordance with yet another embodiment of the present invention a range of approximately 30 - 40% of the TSS of sewage 10 may be removed by the solid biomass removal system 20. In accordance with still another embodiment of the present invention a range of approximately 40 - 50% of the TSS of sewage 10 may be removed by the solid biomass removal system 20. In accordance with another embodiment of the present invention a range of approximately 50 - 60% of the TSS of sewage 10 may be removed by the solid biomass removal system 20. In accordance with yet another embodiment of the present invention a range of approximately 60 - 70% of the TSS of sewage 10 may be removed by the solid biomass removal system 20. In accordance with still another embodiment of the present invention a range of approximately 70 - 80% of the TSS of sewage 10 may be removed by the solid biomass removal system 20. In accordance with another embodiment of the present invention a range of approximately 80 - 90% of the TSS of sewage 10 may be removed by the solid biomass removal system 20. In accordance with another embodiment of the present invention more than approximately 90% of the TSS of sewage 10 may be removed by the solid biomass removal system 20.

Reduction of methane and carbon dioxide emission from a conventional WWTP by removal of solid biomass by the biomass removal system 20 is described in Examples 1-5 hereinbelow.

EXAMPLE l

Approximately 40% of solid biomass, including cellulose, was removed from sewage prior to entering a relatively large scale WWTP of the municipality of Tel- Aviv, Israel. The solid biomass was removed by a solid biomass removal system comprising a series of nettings with apertures of a few microns.

As seen in Fig. 2, following removal of the solid biomass the carbon content of the sewage was reduced by approximately 60%; the organic matter content of the sewage was reduced by approximately 50%; the cellulose content of the sewage was reduced by approximately 70%; the BOD of the sewage was reduced by approximately 30%; the TS of the sewage was reduced by approximately 30%; and the TSS of the sewage was reduced by approximately 60%. Thus it is seen that the solid biomass portion of the sewage entering the WWTP was significantly reduced.

EXAMPLE 2

The gaseous emission reduction was assessed in the relatively large scale WWTP of the municipality of Tel- Aviv, Israel. The assessment was based on the assumption that the WWTP operates in open, anaerobic lagoons, i.e. the digestion of the sewage is performed anaerobically. The reduced gaseous emission is presented in Certified Emission Reduction (CER) units per year. CER is generally defined as a ton of carbon credits, which is an allowance for permitting an emission of a ton of carbon dioxide within a carbon credit system. The carbon credit system was ratified in conjunction with the Kyoto Protocol aiming to reduce global carbon dioxide emissions. Additional gaseous emissions are measured in equivalent CER units. For example, one ton of emitted methane is quantitated as 21 CER units, though it is appreciated that the quantification of methane to CER units may vary.

Approximately 40% of solid biomass, including cellulose, was removed from the sewage prior to entering the WWTP. The solid biomass was removed by a solid biomass removal system comprising a series of nettings with apertures of a few microns. The solid biomass portion of the sewage entering the WWTP was significantly reduced. Consequentially the methane emission, which is due to anaerobic processing within the sewage management system, was decreased by approximately 141,000 CER units per year. Additionally, the methane emission due to landfilled sludge, was decreased by approximately CER 10,000 units per year.

Removal of the solid biomass reduced the operational electrical consumption of the WWTP by approximately 18%, thereby reducing the gaseous emission by approximately 13,000 CER units per year.

A graph showing the CER units per year gained in Example 2 is shown in Fig. 4.

EXAMPLE 3

The gaseous emission reduction was assessed in a relatively large scale WWTP of the municipality of Tel-Aviv, Israel. The assessment was based on the assumption that the WWTP operates in open, aerobic lagoons, i.e. the digestion of the sewage is performed aerobically. The reduced gaseous emission is presented in CER units per year.

Approximately 40% of solid biomass, including cellulose, was removed from the sewage prior to entering the WWTP. The solid biomass was removed by a solid biomass removal system comprising a series of nettings with apertures of a few microns. Consequentially, methane emission due to landfilled sludge, was decreased by approximately 25,000 CER units per year.

Removal of the solid biomass reduced the operational electrical consumption of the WWTP by approximately 18%, thereby reducing the gaseous emission by approximately 13,000 CER units per year.

It is noted that due to aerobic operation of the WWTP methane is not emitted into the atmosphere during operation of the WWTP.

A graph showing the CER units per year gained in Example 3 is shown in Fig. 4.

EXAMPLE 4

The gaseous emission reduction was assessed in a relatively small scale WWTP of about a 15% of the size of the municipal Tel Aviv WWTP. The assessment was based on the assumption that the WWTP operates in open, anaerobic lagoons, i.e. the digestion of the sewage is performed anaerobically. Approximately 40% of solid biomass, including cellulose, was removed from the sewage prior to entering the WWTP. The solid biomass was removed by a solid biomass removal system comprising a series of nettings with apertures of a few microns. The solid biomass portion of the sewage entering the WWTP was significantly reduced. Consequentially the methane emission, which is due to anaerobic processing within the sewage management system, was decreased by approximately 21,150 CER units per year. Additionally, the methane emission due to landfilled sludge, was decreased by approximately CER 1,500 units per year.

Removal of the solid biomass reduced the operational electrical consumption of the WWTP by approximately 18%, thereby reducing the gaseous emission by approximately 1,950 CER units per year.

A graph showing the CER units per year gained in Example 4 is shown in Fig. 5.

EXAMPLE 5

The gaseous emission reduction was assessed in a relatively small scale WWTP of about a 15% of the size of the municipal Tel Aviv WWTP. The assessment was based on the assumption that the WWTP operates in open, aerobic lagoons, i.e. the digestion of the sewage is performed aerobically. The reduced gaseous emission is presented in CER units per year.

Approximately 40% of solid biomass, including cellulose, was removed from the sewage prior to entering the WWTP. The solid biomass was removed by a solid biomass removal system comprising a series of nettings with apertures of a few microns. Consequentially, methane emission due to landfilled sludge, was decreased by approximately 3,750 CER.

Removal of the solid biomass reduced the operational electrical consumption of the WWTP by approximately 18%, thereby reducing the gaseous emission by approximately 1,950 CER units per year.

A graph showing the CER units per year gained in Example 5 is shown in Fig. 5. Reference is now made to Fig. 3, which is a simplified block diagram of a system for reducing gaseous emission, resulting from combustion of fossil fuels, by utilizing elements of the system of Fig. 1, constructed and operative in accordance with an embodiment of the present invention. As seen in Fig. 3 the removed solid biomass portion 30 of Fig. 1 is introduced into the solid biomass processing system 60, for further processing thereof.

For example, the solid biomass portion 30 within the solid biomass processing system 60 may be sterilized by any suitable means. Additionally, the solid biomass portion 30 may be ground in a grinding device by any suitable means, such as by employment of a screw press, a filter or a blender, a ball grinder, a stone or knife grinder, for example. The solid biomass portion 30 may be ground to any suitable particle size, such as to particles with a length of approximately less than 1 mm, for example.

The solid biomass portion 30 may be introduced into a drying device for partially drying solid biomass portion 30. The drying device may employ any suitable method for partially drying the solid biomass portion 30, such as drying by evaporation employing heat treatment, cryogenic treatment, vacuum, a press, such as a screw press, a drum dryer or a combination thereof.

The solid biomass portion 30 may be thereafter pressed in a pressing device employing any suitable means, such as use of a screw press or a filter press. The solid biomass portion 30 may thereafter be packaged in a packaging device by any suitable means, such as by employing vacuum packing or pellet packing in a pellet machine, for example.

A resulting combustion product 70 is obtained from the system described hereinabove. The combustion product 70 is used for combustion of materials and may be used instead of fossil foil coal. For example, the combustion product 70 may be wood pellets. Thus, utilizing the combustion product 70 allows for reducing gaseous emission resulting from combustion of fossil fuels.

It is appreciated that the order of using the devices described hereinabove may be alternated so as to produce combustion product 70 from solid biomass portion 30.

A skilled artisan will appreciate that in the process of producing combustion product 70 some of the devices described hereinabove may be obviated without compromising the quality of the produced combustion product 70. Additionally, the solid biomass portion 30 may be used for combustion without processing thereof within the solid biomass processing system 60.

It is noted that additional products, operative to reduce gaseous emission during combustion, may be produced by processing the solid biomass portion 30 within the solid biomass processing system 60. For example biofiiels, such as ethanol may be produced.

Reduction of carbon dioxide emission due to processing the solid biomass portion 30 to produce a combustion product 70 is described in Examples 6 and 7 hereinbelow.

EXAMPLE 6

Approximately 40% of solid biomass, including cellulose, was removed from the sewage prior to entering the relatively large scale WWTP of the municipality of Tel-Aviv, Israel, described in reference to Examples 2 and 3 hereinabove. The solid biomass was removed by a solid biomass removal system comprising a series of nettings with apertures of a few microns. The removed solid biomass was sterilized and dried in a sterilization oven at 105°C. Thereafter the dried solid biomass was pressed and packaged in a pellet machine. A yield of approximately 22 ton of wooden pellets per year may be thus obtained. The potential heat produced by such a quantity of wooden pellets is approximately 50,544,054 Terajoules. Assuming that combustion efficiency is approximately 90%, the equivalent amount of oil needed to yield 50,544,054 Terajoules is approximately 1787.3 ton per year, thus resulting in a reduction of carbon dioxide emission by approximately 55,000 CER units per year.

A graph showing the CER units per year gained in Example 6 is shown in Fig. 4.

EXAMPLE 7 Approximately 40% of solid biomass, including cellulose, was removed from the sewage prior to entering a small scale WWTP described in reference to Examples 4 and 5 hereinabove. The solid biomass was removed by a solid biomass removal system comprising a series of nettings with apertures of a few microns. The removed solid biomass was sterilized and dried in a sterilization oven at 105°C. Thereafter the dried solid biomass was pressed and packaged in a pellet machine. A yield of approximately 3.3 ton of wooden pellets per year may be thus obtained. The potential heat produced by such a quantity of wooden pellets is approximately 7,581,608 Terajoules. Assuming that combustion efficiency is approximately 90%, the equivalent amount of oil needed to yield 7,581,608 Terajoules is approximately 268.095 ton per year, thus resulting in a reduction of carbon dioxide emission by approximately 8,250 CER units per year.

A graph showing the CER units per year gained in Example 7 is shown in Fig. 5.

It is noted that the method for reducing greenhouse gas emission described hereinabove may be used to reduce all greenhouse gases, such as carbon dioxide, methane, sulfur dioxide and nitrogen oxides.

It will be appreciated by persons skilled in the art that the present invention is not limited by what has been particularly shown and described herein above. Rather the scope of the present invention includes both combinations and subcombinations of the various features described hereinabove as well as variations and modifications which would occur to persons skilled in the art upon reading the specifications and which are not in the prior art.

Claims

CLAIMS:

1. A method for reducing gaseous emission from a sewage management system comprising: removing at least 20% of a solid biomass portion of a sewage suspension, which flows within said sewage management system, thereby reducing the gaseous emission.

2. A method for reducing gaseous emission from a sewage management system comprising: removing at least 20% of a Total Suspended Solid (TSS) portion of a sewage suspension, which flows within said sewage management system, thereby reducing the gaseous emission.

3. A method for reducing gaseous emission from a sewage management system comprising: removing a solid biomass portion of a sewage suspension, which flows within said sewage management system, thereby reducing any one of the following: a carbon content of said sewage suspension by approximately 10% - 90%; an organic matter content of said sewage suspension by approximately 5% - 95%; a cellulose content of said sewage suspension by approximately 20% - 95%; a Biological Oxygen Demand or Biochemical Oxygen Demand (BOD) of said sewage suspension by approximately 10% - 90%; a Total Solid (TS) content of said sewage suspension by approximately 5% - 90%; and a Total Suspended Solid (TSS) content of said sewage suspension by approximately 10% - 90%, thereby reducing the gaseous emission.

4. A method according to claim 1 wherein said removal of at least 20% of said solid biomass portion results in a reduction of at least 20% of said gaseous emission.

5. A method according to any one of claims 1-4 wherein said reducing of said gaseous emission is comprised of at least one of the following: reduction of methane emission during anaerobic processing of said sewage suspension within said sewage management system following said removal of said solid biomass portion therefrom; reduction of methane emission during landfilling of sludge produced by processing of said sewage suspension within said sewage management system following said removal of said solid biomass portion therefrom; and reduction of carbon dioxide emission due to reduced electricity consumption during operation of said sewage management system.

6. A method according to claim 1 or 3 wherein removed said solid biomass portion is processed so as to produce a combustion product for replacing fossil foils, thereby further reducing gaseous emission caused by combustion of fossil foils.

7. A method according to any one of claims 1-6 wherein said gaseous emission comprises a methane emission and a carbon dioxide emission.

8. A method according to any one of claims 1-7 wherein said gaseous emission comprises a methane emission, a carbon dioxide emission, a sulfur dioxide emission and a nitrogen oxide emission.

9. A method according to any one of claims 1-8 wherein Certified Emission Reduction (CER) units are earned by said reduction of said gaseous emission.

10. A method according to any one of claims 1-9 wherein said sewage management system is a Wastewater Treatment Plant.

11. A system for reducing gaseous emission from a sewage management system comprising: a solid biomass removal system operative to remove at least 20% of a solid biomass portion of a sewage suspension, which flows within said sewage management system, thereby reducing the gaseous emission.

12. A system for reducing gaseous emission from a sewage management system comprising: a solid biomass removal system operative to remove at least 20% of a Total Suspended Solid (TSS) portion of a sewage suspension, which flows within said sewage management system, thereby reducing the gaseous emission.

13. A system for reducing gaseous emission from a sewage management system comprising: a solid biomass removal system operative to remove a solid biomass portion of a sewage suspension, which flows within said sewage management system, thereby reducing any one of the following:: a carbon content of said sewage suspension by approximately 10% - 90%; an organic matter content of said sewage suspension by approximately 5% - 95%; a cellulose content of said sewage suspension by approximately 20% - 95%; a Biological Oxygen Demand or Biochemical Oxygen Demand (BOD) of said sewage suspension by approximately 10% - 90%; a Total Solid (TS) content of said sewage suspension by approximately 5% - 90%; and a Total Suspended Solid (TSS) content of said sewage suspension by approximately 10% - 90%, thereby reducing the gaseous emission.

14. A system according to any claim 11 wherein said removal of at least 20% of said solid biomass portion results in a reduction of at least 20% of said gaseous emission.

15. A system according to any one of claims 11-14 wherein said reducing of said gaseous emission is comprised of at least one of the following: reduction of methane emission during anaerobic processing of said sewage suspension within said sewage management system following said removal of said solid biomass portion therefrom; reduction of methane emission during landfilling of sludge produced by processing of said sewage suspension within said sewage management system following said removal of said solid biomass portion therefrom; and reduction of carbon dioxide emission due to reduced electricity consumption during operation of said sewage management system.

16. A system according to claim 11 or 13 wherein removed said solid biomass portion is processed in a solid biomass processing system so as to produce a combustion product for replacing fossil foils, thereby further reducing gaseous emission caused by combustion of fossil foils.

17. A system according to any one of claims 11-16 wherein said gaseous emission comprises a methane emission and a carbon dioxide emission.

18. A system according to any one of claims 11-17 wherein said gaseous emission comprises a methane emission, a carbon dioxide emission, a sulfur dioxide emission and a nitrogen oxide emission.

19. A system according to any one of claims 11-18 wherein Certified Emission Reduction (CER) units are earned by said reduction of said gaseous emission.

20_. A system according to any one of claims 11-19 wherein said sewage management system is a Wastewater Treatment Plant.