AU2011339363A1

AU2011339363A1 - Anaerobic treatment method and device

Info

Publication number: AU2011339363A1
Application number: AU2011339363A
Authority: AU
Inventors: Takao Hagino; Naoaki Kataoka; Masato Nishiwaki
Original assignee: Swing Corp
Current assignee: Swing Corp
Priority date: 2010-12-10
Filing date: 2011-12-09
Publication date: 2013-09-05
Anticipated expiration: 2031-12-09
Also published as: JP2016117066A; JPWO2012077778A1; JP6121165B2; CN103347824A; KR20140032362A; KR101885070B1; CN103347824B; JP6121589B2; WO2012077778A1; AU2011339363B2

Abstract

The purpose of the present invention is to provide an anaerobic processing method and a device, whereby: an anaerobic digestion device can be made more compact; the generation of phosphorous, siloxane, and other precipitates is reduced; sludge generated at wastewater processing facilities, etc., is stably and efficiently anaerobically digested; biogas (especially methane gas) can be efficiently recovered; digested sludge can be efficiently dewatered; and cost is reduced. Provided is an anaerobic processing method that includes: a preprocessing step that solid/liquid separates a coagulated sludge, which is prepared by adding a coagulant to sludge, into a sludge concentrate with a sludge concentration of 4-12% and a separated liquid; an anaerobic digestion step that anaerobically digests the sludge concentrate and also recovers biogas; a step for preparing a digested sludge coagulant by mixing a coagulant and at least one of either the separated liquid and water, with the anaerobically digested sludge prepared in the anaerobic digestion step; and a step for dewatering a digested sludge concentrate obtained by solid/liquid separating the digested sludge coagulant. Also provided is a device for implementing said processing method.

Description

DESCRIPTION ANAEROBIC TREATMENT PROCESS AND APPARATUS TECHNICAL FIELD [0001] The present invention relates to a process and an apparatus for the anaerobic treatment of sludge. BACKGROUND ART [0002] The anaerobic digestion treatment of sludge is a technology that has b-en applied as an energy saving process for a long time, since the treatment produce less sludge than an aerobic treatment, quickly kills off pathogenic microorganisms and parasite eggs and stabilizes the sludge, consumes little power since it requires no oxygen supply, and produces biogas whose main component is methane gas. On the other hand, the technology holds many problems in view ofthe large capacity required for an anaetobic digestion tank facility, the high cost of chemicals used in treating digested-sludge, and the difficulty in reducing the water content of dewatered sludge due to its lox dewaterabilitv [0003] Thus, it is still common lin the present method for disposing sludge to dewater and dispose sludge in a landfill or dewater and incinerate it, without anaerobically digesting sludge.. An example of a conventional anaerobic treatment of sludge is shown as a flowchart in Figure 6. The process flow is described below [0004] Sludge I is sent to a storage system 2, then it is sent to a solid-liquid separation device 6 fM solid-iquid separation into a concentrated sludge 7 and a separation effluent of which the concentrated sludge 7 is sent to an anaerobi digestion device 9 where biogas 10 and an anaerobically-digested-sludge I are produced. Biogas 10 is sent toabiogas tank 101, then t is sent to a gas-using facility 102 (eg. gas turbine, biogas i er ga s l uap. or a drier heat source) or to a surplus gas combustion system 1 03 The anaerobically-digested sludge 11 is sent to a digested-sludge flocculation device 12 where a separation effluent 14 is separated and a flocculated digested sludge 15 is prepared, of which the flocculated digested sludge 15 is sent to a dewatering device 16 where a separation effluent 1 7 is separated and a dewatered cake 18S is prepared. The separation effluent 8, separation effluent 14, and separation effluent 17 are sent to a wastewater treatment plant 104 or the like. A fiocculant is often added in the digested-sludge flocculation device 12. [0005] Meanwhile, Patent Document I presents a treatment methodfor night soil, garbage and|sludge which treats sludge of an organic wastewater treatment plant, sludge such as private sewage treatment tank sludge, night soil and garbage containing animal and plants wastes with reduced energy consumption, and which sanitarily converts night sol and insanitary screenresidue in the private sewage treatment tank sludge to compost and solid fuel the treatment consisting of (a) a pretreatment step for performing solid-liquid separation of night soil mixed with sludge. (b) an anaerobic digestion step for anaerobically digesting solid matter separated in the pretreatment step directly without dewatering it, e) an anaerobic digestion step for anaerobically digesting garbage containing animal and plants wastes and solid matter (d) a dewatering step for dewatering and separating outflowing liquid of the anaerobic digestion step into solid matter and separation water and (e) a biological treatment step for biologicaly oxidizing and denitrifying the separation water of the pretreatment step and the separation water from the dewatering step. [0006] Patent Document 2 presents a sludge treatment method and a system therefore which can maximize the total efficiency of processes for concentrating and dewatering two kinds of wastewater sludge generated in the wastewater treatment, namely primary settled sludge and excess sludge, by concentrating the sludge in a single system and concentrating it to a sludge concentration optimal for a subsequent dewatering process and maintaining the state the treatment method including the following steps: the primary settled sludge and the excess sludge respectively generated from a primary settling tank and a fial setting tank in a wastewater treatment system are mixed and stored; a flocculant is added to the mixture sludge to perform primary flocculation treatment the mixture sludge after the primary flocculation treatment is concentrated to a shluge concentration of 6-8%; a flocculant is added to the mixture sludge after the concentration treatment to perform secondary flocculation treatment and the mixture sludge after the secondary flocculation treatments subjected to dewatering treatment. [0007] Additionaly, Patent Document 3 presents sit-type concentration machine that increases the pressurization effect as well as the carrying capacity of the solid-liquid separator. CITATION UST PATENT DOCGUMENTS [0008] Patent Document 1: Japanese unexamined patent publication No, 10-216785 Patent Document 2: Japanese unexamined patent publication No. 2007-264758 Patent Document 3:Japanese unexamined patent publication No, 200321 1293 SUMMARY OF INVENTION TECHNICAL PROBLEM [0009] The greatest problem in an an aaerbi digestion treatment of sludge produced by wastewater treatment plant and the like as that it required an anaerobic digestion tank of a large capacity due to the IHRiT(Hydraulic retention time) of normal anaerobic digestion treatments being 20 to 30 days For example, a sludge treatment of sludge having a T'IS Total Solids) concentration of 3 wt% at a treatment rate of 100 m/day nonnally requires a large anaerobic digestion tank of 2000 to 3000 n to be built. Further, problems in treating digested-siudge were a high chemical cost for sludge flocculation and dewatering treatment and a low dewaterability of sludge that made it difficult to reduce the after content of sludge. Such problems result from protein being deemposed in the anaerobic digestion of sludge, thus producing ammonia nitrogen and increasing MA alkalinity (acid consumption of up to pH 4.8) to at least about 3,000 mg aC0L, which puls the pH condition away from the weak acidity region which is considered to be the optimum phi condition for sludge flocculation. Another problem was that the decomposition of coarse suspended solids (fiber) in the sludge by sludge digestion reduced the coarse suspended solids content, which contributes greatly to water removal in the sludge dewatering process, and lead to an increase in the water content of dewatered wakes. A further problem was that precipitates of phosphorous, calcium and the like were produced in anaerobic digesion tanks, pipes and the 4 like. In addition, silicon in the astewater is normally in the form ofiloxan derived from silicon compounds including silicon ols in shampoos, conditioners, cosmetics and the like. A siloxan is an organic compound having a silicon-oxygen bond whose main chain is Si-O and whose side chain is hydrocarbon. Examples of siloxans include a linear or cyclic siloxan composed of 2 to 6 siicon atoms and having a methyl group as a hydrocarbon group. Since siloxan has low water sohubility, it is distributed into biogas when sewage sludge is anaerobically digested. Accordinglymany cases are known of siloxan precipitating as scales on the generation facility, such as a gas engine, and peripheral equipment when power is generated using biogas, and reducing power generation efficiency and degrading facility maintenance, and a preventative measure is a key issue. [0010] The present invention was made in view of the above problemand its object is to provide a low cost anaerobi treatment process and an apparatus that downsize the anaerobic digestion devices well as reduce the production of precipitates including phosphorous, calcium and siloxan (silicon compounds having a siloxan bond), performs a stable and efficient anaerobic digestion of sludge produced in the wastewater treatment plant, as well as effiiently recover biogas (especially methane gas), and efficiently dlewater the digested sludge. SOLUTION TO PROBLEM [0011] The following anaerobic treatment process and anaerobic treatment apparatus is provided according to the present ihention. 1) An anaerobic treatment process comprising: a pretreatment step for subjecting a flocculated sludge to a solid-iquid separation into concentrated sludge having a sludge concentration of 4 to 12 wt% and a separation effluent, wherein the focculated sludge was prepared by adding a foeculant to a sludge; an anaerobic digestion step for anaerobically digesting the concentrated sludge and recovering biogas; a step for preparing a flocculated digested-sldge by mixing a tlocculant and at least one of the separation effluent and water with an anaerobically-digested-sludge prepared in - 5 the anaerobic digestion step; and a step of dewatering a concentrated digested-sludge that was obtained by performing solidliquid separation on the flocculated digested-sludge. 2) An anaerobic treatment apparatus comprising: a flocculation tank for preparing a flocculated sludge by adding a loceculant to sludge; a pretreatment sludge concentration device for subjecting the flocculated sludge to a solidliquid separation into a concentrated sludge having a sludge concentration of4 to 12 wt% and a separation effluent to pr-pare. concentrate ted sludge; an anaerobic digestion device for anaerobically digesting the concentrated sludge and recovering biogas; a digested-sludge flocculation device for preparing a flocculated digested-sludge by mixing a floculant and at least one of the separation effluent and water with an anaerobically-digested-sludge prepared by the anaerobic digestion device; and a device for dewatering a concentrated digested-sludge that was obtained by subjection the flocculated digested-sludge to a solid-liquid separation. [00121 In the trt e htd ofthe present invention, the concentrated Judge prepared by solid-iquid separation in the pretreatment step contains sludge at 4 to 12 wt%, which is at least 15 to 2tines thicker than conventional methods. Since anaerobic digestion treatment was performed on the concentrated sitdge, the anaerobically-digested-sludge in the present invention has a higher M alkalinity and ammonia concentration than the anaerobically digested-sludge of conventional methods. Accordingly, to obtain a dewaterable floc by adding a flocculant to an anaerobicalydigested-sludge per se would require a large amount of flocculant, in the present invention, a dewaterable flocculated digested-sludge is obtained by nixing at least one of the separation effluent or water obtained in the pretreatment step into the anaerobically-digested-sludge to dilute it, and smoothly produces flocculated digested-sludge by the sludge flocculation reaction of the anaerobically-digested sludge and the added flocculant to reduce the amount of flocculant to be injected. Further, -6 in the pretreatment step of the present invention, the flocculated sludge prepared by adding a flocculant is separated into concentrated sludge and separation effluent, which alows the separation efuent to contain useful resources that are water-soluble or hydrophilic. such as phosphorous, and allows efficient recovery of the useful resources. Additionally, since the pretreatment step, which allows the recovery of useful resources, is performed before the anaerobic digestion step, the amount of materials in the concentrated sludge to be sent to the anaerobic digestion step, such as phosphorous and siloxan, is reducedand the reduction together with the high sludge concentration allows less precipitates, such as phosphorous and siloxan. to be produced in the anaerobic diestion tank. [0013] in the present invention. "%" indicates "mass%" unless otherwise noted. 'The anaerobic treatment apparatus of the present invention can include meanssuch as pipes, pumps and valves, to send sludge from one specific device mentioned above to another as necessary. ADVANTAGEOUS EFFECTS OF INVENTION 001 4] 'h he present invention not only decomposes organic maters by anaerobic digestion of sludge in wastewater treatment plant and the like, but also allows efficient recovery of biogas (especially methane gas), and thus, significantly improves the energy recovery efficiency Especially concerning the technical problems of the conventional treatment method, which are the need for a large capacity anaerobic digestion tank facility, a high chemical cost for digested-slhdge treatment, and the difficulty in lowering the water content of dewatered sludge due to the low dewaterabiity of sludge, the present invention can concentrate sludge to a high concentration using a concentration device whose running cost is low, largely reduce the anaerobic digestion capacity. and further improve dewatering operation on an anaerobicallydigestedssludge of a low dewateability, and thus, provide a low cost anaerobic digestion system that can eflently dewater digested-sludge. Further, the present invention can reduce the amount of phosphorous, calcium, siloxan and the like to be introduced into the anaerobic digestion tank to about half the conventional amount, which leads to the reduction of precipitates including those of phosphorous, calciumand siloxan being formed in the anaerobic digestion tank, and thus, contributes to cutung maintenance and management Costs of the anaerobic digestion tank, pipes and the like as well as enables an effident recovery of useful resources, such as phosphorous. BRIEF DESCRIPTION OF DRAWINGS [0015] Figure 1 is an illustrative diagram showing the arrangement of the treatment apparatus according to an embodiment of the present invention Figure 2 is an illustrative diagram showing the arrangement ofthe treatment apparatus according to an embodiment of the present invention. Figure 3 is an ilustrative diagram showing the arrangement of the treatment apparatus according to an embodiment of the present invention. Figure 4 is an illustrative diagrin showing the arrangement of the treatment apparatus according to an embodiment of the present invention. Figure 5 is an illustrative diagram showing the arrangement of the treatment apparatus according to an embodiment of the present invention. Figure 6 is an illustrative diagram showing the arrangement of a conventional treatment apparatus. DESC RIION OF EMB|ODIMENTS [0016] Ie present invention is described in more detail below by referring to the drawings as necessary. [0017] The anaerobic treatment process of the present invendon includes a pretreatment step for subjecting a floculated Judge to a soid-liquid separation into Coneentrated sludge having a sludge concentration of4 to 12 wt% and a separatim effluent, wherein the flocculated sludge was prepared by adding a fiocculant to a sludge; an anaerobic digestion step for anaerobically digesting the concentrated sludge and recovering biogas; a step for preparing a flocculated digested-sludge by mixing a fiocculant and at least one of the separation liquid and water with an anaerobicallyqdigestedmsludge prepared in the anaerobic digestion step; and a step of dewatering a concentrated digested-sludge that was obtained by performing solid-liquid separation on the flocculated digeste-sludge.

[0018] In the present invention "sludge" means sludge that is discharged in the step of treating organic substances, such as sewage, night soil and garbage. [00191 The sludge to be treated in the present invention is preferably at least one of primary settled sludge that is produced in the primary settling tank of the wastewater treatment plant and excess sludge thatlis produced in the final settling tank, and mnore preferably a mixed sludge of both. Such sludge is preferably stored in the storage tank and subjected to gravity concentration. [0020] To the sludge discharged from the storage tank, a flocculant is added to prepare flocculated sludge. The amount of focculant to be added is preferably 0.2 to 10 wt% to the SS (Suspended Solids; suspended particles) in sludge and more preferably 0.3 to 06 wt%. [0021] A commonly used flocculant can be used as the flocculent, without any particular limitation. Examples include inorganic flocculantssuch as iron (II) polysuiphate, PAC, or aluminum sulphates; and polymeric organic flocculants (hereinafter referred to as polymeric flocculants), which can each be used singly or in combination, but it is preferable to at least include a polymeric floceulant in use. Polymeric flocculants may include cationie, anionic amphoterie tocculants and the like, and specifically amidine flocculants, acrlamide flocculants, acrylic acid flocculants. [0022] The anaerobic treatment process of the present invenion is described below by steps. [0023] <Pretreatment Step> The pretreatment step is a sludge concentration step for subjecting a flocculated sludge to a solid-liquid separation into concentrated sludge having a sludge concentration of 4 to 12 wt% and a separation liquid, in which the flocculated sludge was prepared by adding a flocculant to a sludge. In the conventional method. the sludge was concentrated by adding a polymer flocculant, so it was anly possible to concentrate the ludge to a concentration of about 3 to 4 wt%, and about 4 to 5 wt% at maximum The present invention allows a high sludge concentration of 4 to 12 wt%. Meanwhile, the separation liquid includes phosphorous calcium and siloxan. [00241 <Anaerobic Digestion Step> Next the above concentrated sludge is sent to the anaerobic digestion step, where it is anaerobically digested and the resulting biogas is simultaneously recovered Digestion of concentrated sludge is performed at 30 to 60"C and preferably at a mesophilic digestion range of 30 to 40 0 C or a thermophlic digestion range of 50 to 601C A preferable pH during the anaerobic digestion is pH 6 to 8.5, and more preferably pH 6. to 80 [0025] In a mixed digestion of the tAow 'ing organic waste liquid and waste matter which includes much fat and oil, a higher temperature provides higher dispersibiity of neutral fat and higher fatty acid, so it is preferable to select a digestion method at a thermophilic temperature of 50 to 60*C Meanwhile, ammonia which results from anaerobic digestion of sludge is easily dissociated at a high pH.I and a high temperature rangeso it should be noted that a high temperature digestion tends to inhibit ammonia The methane production reaction is inhib ited when the NH'N concentration in the digestive juice is at least ,500 mg!L in a mesophilic digestion and at least 2,000 mg/L in a thermophilic digestion, These operation conditions are detenned by taking into account the sludge concentration and the sludge characteristics of the Concentrated sludge, the fluctuation of water amount during anaerobic digestion, and the target treated water quality. [0026] The anaerobic digestion step should nore preferably include a primary digestion step in vhichihe concentrated sludge is subjected to solubilization and acid fermentation treatmnt at a treatment temperature of 30 to 60C and HRT of I to 3 days; and a methane fermentation step for preparing the anaerobically-digestedsiudge by subjecting the digested sludge treated in the pHinary digestion step to a methane fermentation treatment. [0027] The primary digestion step functions to accelerate the anaerobic eatment of the subsequent methane fermentation step, and contributes to reducing HR' in the methane fermentation step, efficiently and stable recovering biogas, maintaining a high and stable coarse suspended solids content ratio, and reducing the fermentation vsosity. In addition, the SS concentration can be adjusted in the primary digestion step. [0028] The methane fermentation step is preferably performed at a treatment temperature of 30 to 60 0 C and HRT of 12 to 20 days, to preferably prepare the anaerobically-digested- - 10 sludge to have a coarse suspended solids content of 3 to 20% against SS, A "coarse suspended solids" in the above "coarse suspended solids content" refers to fibrous substances, such as elulose, particulate substances, and the like, The HRT is more preferably 12 to I5 days, and the coarse suspended solids content is more preferably S to 8% By adjusting the coarse suspended solids content to the above range the dewaterability of the concentrated digested-sludge is improved, and the water content of the dewatered cake can be reduced. [0029] Further in the anaerobic digestion step of the present invention, an organic waste liquid or waste matter introduced from outside, that is, outside the wastewater treatment plant implemented in the present invention, can be treated with the sludge. The organic waste liquid and waste matter from outside include at least organic compounds discharged from facilities, such as a factory or a sewage treatment plant; it may also include sludge and herbs The organic waste liquid and waste matter from outside may be introduced into any of the pretreatment step, the primary digestion step and the methane fermentation step. When the organic waste liquid and waste matter from outside are anaerobieally digested with sludge, the organic waste liquid or waste matter are preferably adjusted to a slurry TS concentration of I to 150% (more preferably 3 to 10% nd added at a mixture condition that provides a slurryS (total solids) ratio of 120% or lower (more preferably 5 to 100%) against a TS of the concentrated sludge. A slurry TS concentration is the TS concentration in a slurry, and the slurry TS ratio is the DS ratio of introduced substances contained in the slurry. The slurry 178 concentration is determined by taking into account the type, concentration, state, introduction frequency of the organic waste liquid and waste matter. Also, the orgame waste liquid and waste matter introduced from outside should preferably be introduced into the anaerobic digestion step after being decomposed physically chemically or biologically. as necessary, to stabilize the digestion reaction. Preferable examples of treatment methods include wet fragmentation. dry fragmentation, heat treatment high-temperature high-pressure treatment, acid or alkali treatment, biological solubilization or acid fermentation. [0030] <Flocculated Digested-sludge Preparation Step> Next, a flocculated digested-sludge is prepared by mixing a flocculant, and at least - II one of the separation effluent of the pretreatment step and water, with an anaerobically digestedsludge prepared by the anaerobic digestion step. [0031] A polymeric focculant and the like is preferable as a flocculant to be added to the anaerobically-digested-ludge. Also, combining an inorganic auxiliary flocculant, such as iron (II) polysulphate or PAC, and a polymeric tlocculant can be effective for improving the clarity of the separation liquid. Polymeric flocculants to be used are not limited to costly amidine flocculantsbut also include relatively low-priced cationic-polymer flocculants like acrylic ester floceulants and methacrylic ester flocculants, and amphoteric flocculants whose cation level is higher than the anion level. An acrylic ester flocculent should preferably have a molecular weight of300 to 65000,000 to produce a flocculated digested-sludge with high sedimentation. [0032] The amount of floeculant to be added fluctuates according to the characteristic of the anaerobically-digested-sludge. and an amount that makes the floe size of the flocculation product a few millimeters is preferable to increase the sedimentation property of the flocculated digested-sludge. Specifically, the floccul ant is added in a range of 1.0 to 25%, preferably in the range of 1 5 to20% against SS in the anaerobically-digested-sludge to obtain a flocculation product having a floc size of 5 to 20 mm, preferably 10 to 20 mm. [0033] The sepai effluent or water so referred to as "dilution water") used in the flocculated digestedsudge preparation step functions to dilute anaerobically-digested-sludge By diluting the concentrated sludge by the separation effluent or water, the electric conductivity of shdge is adjusted to 1200 MSn or lower, preferably 750 mRSn or lower, the Alkalinity of sludge is adjusted to 4000 mg/I or lower, preferably 2500 mg/i or lower, and the temperature of sludge is adjusted to at least 35 0 C, preferably 50 to 75 C, The temperature of diluted sludge can be adjusted by adding the separation effluent or water in the above temperature range, or heating the sludge after addition. Water that can be used as dilution water includes not only the separation effluent that is obtained in the pretreatment step, normal drinking water aid the like, but also, any processing water in the treatment plant that satisfies water quality conditions, such as a relatively low concentration of dissolved - 12 materials (electric conductivity of 500 g/. or lower, M alkalinity of 1 500 mg/L or lower, SS 1500 mg/L or lower, COIcr 15000 mg/L or lower) Further, biological treatment water may be used including activated sludge processing water, or waste fluid from a biological odor control system. [0034] A concentrated digested-sludge and a separation effluent are prepared by performing a solidliquid separation on the resulting flocculated digested-sludge. A preferable concentration rate of the cownentrated digested-ludge is about 15 to 8 times The concentration rate mentioned herein is a quotient obtained by di iding the volume of flocculated digested-sludge by the volume of concentrated digested-sludge. [0035] A flocculant and an opdonal diluted water is added again to the concentrated digested-siudge obtained by solid-liquid separation to prepare a concentrated, flocculated sludge. The fiocculant and diluted water used herein can be the fiocculant and diluted water used in the flocculated digested-sludge preparation step if the concentrated, flocculated sudge has sufficient dewaterability (the TS concentration of concentrated, flocculated sludge is in the range of 4 to 15 w4t%, preferably 6 to 10 wt%), it is sent to the dewatering step as the final flocculated digested-sludge. However, if the reconcentrated flocculated sludge does not have sufficient dewaterability or if the original design requires (if the TS concentration of concentrated, flocculated sludge is lower than 4 wt%) then, the reintroduction of the above flocculant and the subsequent solid-iquid separation or the solid-liquid separation alone can be repeated. The flocculant to be used in the floculant reintroduction can be the same as or different from that used in the flocculated digested-sludge preparation step. [0036] The final flocculated digested-sludge should preferably be a floc of a strength that allows it to barely maintain its particulate floe shape after it is subjected to a shearing force in the latter dewatering step. The flocculant to obtain such flocculated digestedsludge should preferably be a polymeric flocculant, without being limited thereby. The polymeric fiocculant may be those used in the above flocculated sludge preparation step, and it may be the same as or differ from the floccu ant of he pretreatment step. [0037] Dewatering Step> - 13 Next, the flocculated digested-sludge is dewatered and subjected to solid-water separation into a dewatered cake and a separation effluent Te preferable concentration rate of the dewatered cake is about 4 to 10 times in the present invention. The concentration rate herein means the quotient obtained by dividing the volume of focculated digested sludge by the volume of dewatered cake- The separation effluent separated in the dewatered cake preparation step is preferable as diluted water to be used in the step of preparing a flocculated digestedsludge since its SS concentration, M alkalinity and electric conductivity are low. The dewatered cake has low salt content and low water content, so it can be recycled, and is preferable for fabrication, such as composting, carbonizing and fonniing fuel. [0038] <Recovery of Phosphorous and Siloxan> The separation liquid obtained by the pretreatment step contains materials, such as phosphorous, calcium and siloxan. In the present hivention, the separation liquid containing these materials nay be wholly or partially sent to a step for recovering or removing the materialssuch as phosphorus, calcium and siloxan. Phosphorous can be recovered by methods such as the contact-dephosphorization method using hydroxyapatite and the MAP method using ammonium magnesium phosphate [0039] in the MAP method, the seed crystal of MAP is filled into a tank beforehand, such as an upflow tank, and chemicals to supplement the lacking MAP material, such as Mgb and Mg(OH>, are added as desired to the separation liquid, and further, the pH of the separation effluent is adjusted to 78 to 8.5 as desired, and the separation effluent is passed through the reaction tank as an upfiow to enlarge the MAP particle size, then the MAP with the enlarged particle size is taken out of the reaction tank as necessary for separation and recovery. The fine MAP generatedin the reaction tank is recovered from the top of thc tank and retuned to the reaction tank. [0040] Soxan recovery can be performed by adsorbing the separation liquid as gas or mist or in the original state, using adsorbents, such as activated charcoal, silica gel, zeolite, and polymer (e.g. styrene-divinylbenzene copolymer) ,Also, nitrogen gas is heated as necessary and passed through the adsorbent that had adsorbed siloxan to eliminate and recover siloxan.

-14 Siloxan can be treated with a similar adsorbent for the biogas described below, and siloxan can be elhinated and recovered by a similar method. [004]| Since the present invention includes a step of solid-iquid separation into a separation effluent and concentrated siudge as mentioned above, it can reduce the amount of phosphorous, siloxan and the like to be introduced into the anaerobic digestion device from conventional methods. which leads to the reduction of precipitates including those of phosphorous, and sloxan being formed in the anaerobic digestion device, and thus, contributes to cuffing the maintenance and management costs of the anaerobic digestion device, pipes and the like. [0042] <Anaerobic Treatment Apparatus> The anaerobic treatment apparatus of the present invention includes a flocculation tank fo preparing a flocculated sludge by adding a flocculant to sludge;a pretreatment sludge concentration device for subjecting a flocculated sludge to a solid-liquid separation into a concentrated sludge having a sludge concentration of 4 to 12 wt% and a separation effluent; an anaerobic digestion device for anaerobically digesting the concentrated sludge and recovering biogas; a digested-sludge focculation device ior preparing a flocculated digested-sludge by mixing a flocculant and at least one of the separation effluent and water with an anaerobicallydigested-sludge prepared by the anaerobic digestion device; and a device for dewatering a concentrated digested-sludge thatwas obtained by section the flocculated digested-sludge to a solid-liquid separation. [0043] The flocculation tank can be a commonly used flocculationtank. [0044] The pretreatment sludge concentration devie can be a solid-liquid separation tank that performs solid- liquid separation of flocculated ludge into a concentrated sludge and a separation effluent. The soliddiquid separation tank includes a simple tank using gravity concentration, a centrifugal separator using centrifugal concentration, a separator using floatation concentration, a separator using a screen, and a slit-type concentrator, without being limited thereby A preferable type among these is the Aslittype concentrator, and a machine structure of JP 200-211293 A (Patent Document 3), in which the slit plate stops the - 15 material to be treated, the material to be treated is sent to a discharge side on the slit plate by having many disks whose marginal faces are projected on a slit plate having many slits formed thereon eccentrically rotatearound a crank-shaft, in the direction for discharging the material to be treated. In the process, the liquid material drops from the gap with the disk in the slit to be filtered, and the solid material in the material to be treated is separted and captured. The machine structure is further provided with a belt conveyer that is proximate the upper surface of the slit plate and rotates in te discharge direction of the maier to be treatedand deliquors the captured matter on the slit plate by pressing. When the slit-type concentrator is used, a high concentration of 4 to 12 wl% can be stable and surely achieved at a low rumnng cost. [0045] The anaerobiC digestion device includes at least an anaerobic digestion tank. A complete inxture digestion tank is used preferably as an anaerobic digestion tank without being limited thereby. An anaerobic digestion tank requires agitation to prevent scunm development as wel as to provide a homogenous liquid in the tank and an even temperature distribution. A mechanical agitation process is most efficient in the present invention, but an additional pump agitation process or gas agitation process according to the facility environment or the treatment condition is also efetive, Further, the digestion tank an be made of either reinforced concrete or steel as long as it satisfies the above requirements and has a watertight and airtight structure, and an existing anaerobic digestion tank can be used by being modified or updated according to the treatment condition The anaerobic digestion device preferably comprises a solubilizationlacid fermentation treatment tank tbr the sohuilization and acid fermentation treatment of concentrated sludge and a methane fermentation tank for the methane fermentation treatment of digested-sludge treated in the tank, The anaerobic digestion device preferably comprises an external biomass storage device that stores organic waste liquid or waste matter introduced from outside a system and a piping for introducing biomass discharged from the exteral biomass storage device to at last one device selected from a group of the sludge storage device a device for solubilization and acid fermentation treatment, and a methane fermentation device.

16 [0046] The digested-sludge flocculation device comprises with a digested-sludge flocculation tank, a means to introduce diluted sludge, a floeulant addition means, an agitation means, a heating means, and a means for drawing out focculated sludge, as necessary Further, the device can additional comprises an in-pipe mixing device for dilution, [0047] The anaerobic treatment system of the present invention preferably comprises a device for preparing a concentrated digested-sludge from a flocculated digested-sludge [0048I The device for preparing a concentrated digested-sludge preferably comprises a sludge flocculation treatment device for preparing a flocculated sludge with the floculant; a flocculated sludge separation/concentration device fbr preparing a concentrated, foculated sludge by performing solid-liquid separation on the flocculated sludge; and a device for preparing a concentrated, focculated sludge from the concentrated, flocculated sludge by adding a floceulant. [0049] The hocculated sludge separation/concentration device is a device for the solid liquid separation of the flocculated sludge to a concentrated flocculated sludge and a separation effluent. The flocculated sludge separation/concentration device may include a simple tank using gravity concentration, a centrifugal separator using centrifugal concentration, a separator using floatation concentration, a separator using a screen, without being limited thereby. A preferable type among these is the solid-liquid separation device equipped with a screen, for example, a solidlquid separation device equipped with multiple parallel screens arranged at a constant interval and multiple discs, each placed between two adjacent screens, that rotate to physically remove the flocculated sludge in a gap between the adjacent screens and to separate the sludge into a concentrated flocculated sludge and a separation water. The screen slit width is shorter than the floe size of the flocculated digested-sludge by principle, and is preferably 0.1 to 2.5 num [0050] The reconcentrated flocculated sludge preparation device comprises an introduction means for reconcentrated, flocculated sludge, a floccuant addition means, an agitation means and a means for drawing out reconcentrated, flocculated sludge, as necessary.

-17 0051] The device to dewater concentrated digested-udge can normally be a same device as the focculated sludge separatird/oncentration device, in principle, without being minted thereby, but the stress to flocculated digesIed-sludge for separating the dewatered cake should normally be higher than the focculated sludge separation/conentration device, and a well known means can be used. The dewatered cake preparation device preferably comprises a means to add stress to reconcentratedfocculated sludge and a filtration means that is permeated by the separation effluent and that captures the flocculated digested-sludge Means to add stress to the focculated digested-sludge may include a press and a centrifuge. A fitration means may include a screen having an aperture size of 0.1 to 2j mn. [0052] Next, an example of the present invention is explained farther by referring to the drawing. [0053] Figure 1 is a flow diagram showing the first embodiment of the present invention, and an ilustrative diagram showing the arrangement of an anaerobic treatment system, [0054] Sludge 1 is sent to a storage tank 2. Then, the sludge I is discharged from the storage tank 2 and sent to a flocculation tank 3 via a piping In the locculation tank 3, a flocculant 4 is added to the sludge I and a flocculated sludge 5 is prepared. The focculated sludge 5 is sent to the pretreatment sludge concentration tank 6 and subjected to a solid-liquid separation into a concentrated sludge 7 having a sludge concentration of 4 to 12% and a separation effluent 8, The concentrated sludge 7 is sent to the anaerobic digestion tank 9, and a biogas 10 and an anaerobically-digested-udge 1 1 is produced by an anaerbic digesdon of sludge. Biogas 10 is sent to a biogas tank 10L then the biogas 10 is sent to a gas using facility 102 (eg. a gas turbine, a biogas boiler, a gas lamp, and a drier heat source) or a surplus gas combustion facility 103. The anaerobically-digested-sludge 11 is sent to a digested-sludge fiocculation device 12. To the digested-sludge flocculation device 12 is introduced a part of a separation effluent 8 fonned in the pretreatment sludge concentration tank 6. In the digested-sludge flocculation device 12. a separation effluent and a flocculant 13 are added to the anaerobically-digested-sludge 11 and a flocculated digested sludge 15 and a separation effluent 14|are formed The focculated digestedAludge 1 5 from 18 the digested-sludge flocculation devie 12 is sent to the dewatering device 16, where the separation liquid 17 is separated and the dewatered cake 18 is prepared. A part of a separation effluent 8, a separation effluent 14, and a separation effluent 17 are sent to the wastewater treatment plant 104 and the like for phosphorous recovery and other purposes. Note that a siloxan removal or recovery device can be provided before the biogas tank. [00553 Next, Figure 2 is a flow diagram showing the second embodiment of the present invention, and an illustrative diagram showing the arrangement of an anaerobic treatment system, which performs solubilization and acid fennentation treatment in a primary stage of anaerobic digestion. [00560] In the process flow of Figure 1, the concentrated sludge 7 separated in the pretreatment sludge concentration tank 6 is sent to the solubilization and acid fermentation treatment tank 9a before being sent to the anaerobic digestion tank 9, and a digested-sludge 7a tbat has been sohubilized and treated by acid fennentation treatment is produced. The digested-sludge 7a is sent to the anaerobic digestion tank 9, and then treated according to the process flow of Figure 1. [0057] Next, igure 3 is a flow diagram showing the third embodiment of the present invention, and an illustrative diagram showing the arrangement of an anaerobic treatment system, which divides the sludge flocculation treatment of the anaerobicaly-digested-sludge by a flocculant to be performed at two separate timings. [0058] In the present process flow, the process flow of Figure 2 is modified in its step of sending the anacrobicaily-digested-sludge 11 and a part of the separation effluent 8 to the digested-sludge flocculation devie 12, and preparing the flocculated digested-sludge 15 as well as separating the separation liquid 14 through adding a flocculant 13 as follows. [0059] The anaerobically-digested-sludge 11 and the part of separation effluent 8 are sent to the sludge flocculation treatment tank 1 2a,where a flocculant 13ais added to prepare a flocculated sludge 12c. The flocdulated sludge C2 is introduced into the floccuiated sludge separation/concentration device 14A and is subjected to solid-liquid separation into a separation effluent 14 and a concentrated flocculated sludge l2d Then, the concentrated, flocculated sludge 1|2d is sent to the concentrated, flocculated sludge preparation device 12b where a fioeulant 13b added to prepare a reconcentrated, flocculated sludge ,which is recognized as the final flocculated digestedsludge 15 [0060] Next, Figure 4 is a flow diagram showing the fourth embodiment of the present invention, and an lllustrative diagram showing the arrangement of an anaerobic treatment system, which is the process flow of Figure 3 modified by an additional step of adding a biological treatment water 19 to the sludge flocculation treatment tank l2a to dilute sludge. with other processes being the same as Figure 3. [0061] The biologically treated water may include an activated sludge effluent, biological odor-controlled effluent, nitrification-denitrfication effluent. The type and concentration of the content material of the biologically treated water are determined according to the purpose of the treatment, since they affect the type and addition amount of fiocculant and consequently its cost. [0062] Next Figure 5 is a flow diagram showing the fifth embodiment of the present invention, and an ilustratime diagram showing the armangement of an anaerobic treatment system whieh is the process flow of Figure 4 modified by subjecting the organic waste liquid and waste matter introduced from the outside to the anaerobic digestion treatment as well, with other processes being the same as Figure 4. [0063] The organic waste liquid and waste matter 20 in the present flow is stored in the biomass storage tank 21 as a slurry. The slurry 22 from the biomass storage tank 21 has its IS concentration adjusted as required, then it is introduced into at least one ofthe storage tank 2, the solubilization/acid fermentation treatment device 9a, and the anaerobic digestion device 9 to be treated. [0064] The anaerobic treatment system of Figures 1 to 5 can run by automatic control or batch processing, or a combination of both. The temperature control of various types of sludge can be automated as wella EXAMPLES [0065] Tlhe Exsamples of the present invention are described below. T he sewage siude 20 produced in the A Sewage Treatment Plant was subjected to an anaerobic treatment test of the present invention Note that the present invention is not limited by the Examples in any way. [0066] In the testa cationic-polymer focculant (mean molecule amount 3000,000) was added to the sludge at 014% (against S)and mixed for focculation treatment, then, it was subjected to solid-liquid separation into a conentrated sludge and a separation effluent in the mechanical concentrator equipped with a back pressure plate. The characteristics of sludge, concentrated sludge, and separation liquid are shown in Table 1 [0067] Table 2 shows an anaerobic digestion test condition in the anaerobic digestion device, The anaerobic treatment test is performed by using a complete mixture digestion test device (total volume 30 , effective volume 25 1, jacket warm water circulation type) of heat-resistant vinyl chloride. Further jar fermentor MDL produced by Tokyo Rikakikai Co., Ltd (a complete mixture type oftotal volume 10, operates at a depth of 4 L) for a solubilization/acid fermentation device The anaerobic treatment system (digestion tank) was operated at 37 0 C, and the solubilization/acid fermentation device (solubilization tank) was operated at 45C. Note that a high temperature anaerobic treatment test was performed at 55"C in Comparative Example 2. The materials mere input using a tube pump RP-60| (produced by Tokyo Rikakikai Co. tdand the input was at a frequency of 4 to 8 times a day under timer-control. 0068] [Example 1] The test was performed according to the process fow of Figure 1 [0069] [Example 2] The test was performed according to the process flow of Figure 2. The treatments of Figures 3 and 4 were also performed asthe dewatering treatmentfanaerobicaly digested-sludge. [0070] [Comparative Example] The test was performed according to the process flow of Figure 6. Note lhat the floculated digested-sludge 15 was prepared by sludge floccedation using a polymeric flocculamt. [0071] [Table I] Table 1 Characteristics of Sewage Sludge Samples ___ - -...............- - - -- - --- ----... Sludge Concentrated Sepaao ~2 Sige Effluent ___PH ---. 2 535 Mi alkalinty (mfrgL ac CaCQ;) 600 950j 530 T- ---- - - - ----.... -- 72. 7 VTS % 86 87 884 ".IV 71.837 VSS (%) 88 88 % SS rate)37 35 Ri-N --------------------- 4,280-4 T-P (mgEL) 615 1,1360 156 * unit mg/L [0072] [Table 2] Table 2 Anaerobic Treatment Test Conditions C.ompar C ompar ExmI Example 2 _______Example I Example2 Anaerobic Treatment Digestion Digeston Digestion Solubilizatio Digestion 4Tank Tank lank Tank Tank Tank Treatment C )5 4 37 HlRT (days) 29 8 41 2.5 12 0 nrouedlteil0 Sludg Concentrated sludge .Introduced Material - (-g) 29,500 72,700 IS Concentratio __ introduced Material (%/) 86 87 VTS Concentration - - - - - - - - - - - ... . ... ....... [0073] The following method wa s used for aayi - TS (Total solids, total residue); weight of residue after evaporation at 1 05 0 C (11.8 K 0102) - VTS (Volatile total solids, ignition loss); loss on ignition at 600cC (JIS K 0102) - 88 (Suspended solids, suspended particles); weight of precipitates from a centrifugal separation at a rotation of 3,000 rpm, for 10 minutes (J11S K 0102) -VSS (Volatile suspended solids, volatile suspended particles); loss on ignition at 600 0 C of suspended particles (i1S K 0102) -CODc Chemnical Oxygen D1emand); potassium diehromate method (IS K 0102) ~ BOD) (Biochernical Oxygen Demand); sodium azide modification to the Winkier method (JIS K 0102) - Protein; (Kijdabh n itrogen-amma nitrogen)x6:25 - Volatile organic acid (VFA); high performance liquid chromatograph (Elmer Optics, ERC 8710, detector RI, column Shodex RSpak KC-S 1, column temperature 600C, mobile phase 0.1% phosphoric acid) - Methane gas, carbonic acid gas; gas chromatography (GL Science 00-323 detector TD, TCD current 120 A, separation column Active Carbon 30/60, column temperature 95*0, carrier gas 1-e) ~ Siloxan in the digestion gas: Quantitative analysis is performed using a gas chromatograph mass spectrometer CC/MS to measure sioxan that has been concentrated after it had been captured by passing the digestion gas through the hexane solution at a flow rate of 0 6 L/ninute. The decamethyleycopentasiloxane (D5 of cyclic siloxan that is said to be the largest in content in the sewage sludge digestion gas was analyzed by quantitative analysis. -Soluble fraction; filtrate at CF/Bi (Rm) - M alkalnity, titration to pH 48 of a superIatant liquor from a centrifugal separator rotated at 3,000 rpm for 3 minutes by adding a hydrochloricsolution of 0.1 mo (sewage test method) - Coarse suspended solids; a coarse suspended solids analysis by using a sieve of a nominal dimension of 74 pm (sewage test method) [0074] - 23 [Table 3} Table 3 Anaerobic Treatment Result (ornoar Cornp'r ExampleFapz I xrnpe 1Exar1p ile____ D gest on D gestion Digestion Solubilization Digstiim ...... ---- -h kl - --- n TanuT n introdcedMa Generated (xas (L NTPdayj 10 180 5 2 3 56 Methane ~as (0' 65 6 64 3.5 66 Siloxn ~ tin 36 89 3 3 No analyi 4 8 ss _ 7 9 7a . C1 ..... 148 1 13. 3 2 3.8 3 SolubieCODc- 1 ' 056 06 4A 5 DOD I~ g/L 4 0 0~No analys' 0 Volatile organs (ngL as acetl 8 70 27 10.800 36 acid _______acd1 ____ ___ Coarse suspended % e solids (,3 ne '87 173 deco. si--nn .. --- 3 1 rate- --,----- ..... V TS de..n.osit.n 2.66 62 15 6 rate (0)6 Methane gas d Lintroduti 0on 0 34 0 32 00006 09 Dioe.ti.. 1iavno -% --- 0-- -5 0h t - 1) calculated from the difference between the iroduced singe and the digestion solution ot each material 2) D: digestion ratio VSs A vs 1 organic fraction of introduced x= -1~~0~~-sludge (%4) VS . A .vs 2 : organic fraction of digested 1 2 sludge ('%) A,. inorganic fraction of introduced sludge (%)

A

2 : inorganic fraction of digested sludge (%I [0075] As showna in an anaerobicetreatment test result of Tabile 3. it can be understood that the TS decompostion rate, the VTS decomposition rate, and the methane gas generation rate -24 ofthe anaerobic treatment of Examples 1 and 2 are equivalent to those of conventional arts [0076] Further, when the siloxan D5 concentration in the digestion gas is compared the content rate is low in Examples I and 2. which leads to a presumption that the decrease of the siloxan concentration in the digestion gas occurs when the digested-sludge SS fraction, maintained at a high concentration, adsorbs siloxan compounds. [0077] Further, when the coarse suspended solids are compared, the content rate is high in Examples I and 2 which shows that the sludge condition is more advantageous for sludge dewatering than that of a conventional digested-sludge. [0073] Further, no residue of volatile organic acid was recognized in any of the digestion tanks of the Comparative Examples or the Examples, which shows that the anaerobic treatment reaction proceeded without any problem. [0079] 1'he sludge dewatering treatment performance was assessed using the anaerobically digested-sludge obtained in Comparatie Examples I and 2, and Examples I and 2. A Cationi polymer flocculant (mean molecular weight 3000,000) was used for sludge dewatering, Fdurther, the belt press dewatering machine was used as the dewatering machine at dewatering conditions of a filter loth tonicity of 49 kN/m and a fiter cloth speed of 1O 0rn/minute. [0080] To begin with dewatering treatment was performed for the anaerobically-digested sludge of Comparative Examples I and 2 which resulted in polymeric flocculant injection rates and dewatered cake water contends of Table 4. [0081] [Table 4] Table 4 Dewatering Treatmet Result of Anaerobic Digested-Sludge (1) Compare. Compare, Example 1 Example 2 Ftgurc 6 Injection rate of (% vs. S 1 9 2 0 polymeric flocculantj............_- ..

Dewatered cake (%) 82 83 water cone fnt [0082] Nex, dewaterin treatment wvas oelbmed tbr thd neoialydgeilde of Examples 1 and 2, which resulted in polymeric flocculant injection rates and dewatered cake water contents of Table 5 All dewvatering methods showe--d higher performances than the conventional method, hut the most efficient treatment method was that in Figure 4,in which the introduction of the flocculant was divided into two separate timings, and the biologically treated water was used in combination Further, when a polymeric flocculant was injected into the anaerobieally-digested-sludge obtained in Example I without having the digested sludge diuted with separation water, to flocculate and dewater sludge the polymeric locculant injection rate was 3.8% (against SS) and the dewatered eake water content was 83%. [0083] [Able 5] Table 5 Dewatering Treatment Result ofAnaerobic Digested-Sludge(2 ExampeIFg xml ____ ........ F... ......... - - ----- -_ Floculant Injection ()once once t .c combined with active sludge treatmcwater 'Separation solution: 0 1 S 2.-treatment water =4 Injection rate of (% 8 vs 19 polymeric flocculat 1st time .3% 1st time 1 2% 2nd TImeR 0A% 2nd tine (jA% c ntt___ __ _ * For all tests the rate of anaerobically digestedsiudge separation effluent i 1 0.5, separation effluent is diluted and mixed in the injection of fiocculant, and the M alkalinity at dilutionimixture is 2,500 to 3600 mg/L [0084] [Example 31 Next, Examples of anaerobic treatment performed on sewage sludge, food waste (waste sugar solution and dessert wastes) and grass from river beds is described based on Figure 5, [005] <Treatment Condition - Sewage sludge amount (mixed sludge of primary settled sludge and excess sludge) 30 m 3 /dav (TS concentration 3,14) - 26 - Amount of introduced food waste 1.35 tiday (TS concentration 9.9%) - Amount of introduced grass fom dver beds 0.15 7gday (water content 70.0%) biomass storage tank 3 ir x2 tanks <Pretreatment solid-liquid separator (for mixed sludge from the sewage)> Slt-type concentrator (screen slit width 1.0 mm, equipped with a back pressure plate) Catoni c-polymer flocculant (mean molecular weight 3000,000) injection rate 0.4% (rate against SS) amount of concentrated sludge 12 t/day (TS concentration 1.9%) amount of separation effluent 19.5 mI/day (SS concentration 395 mg) - SS recovery rate 97% pulverizer forcut grass <Anaerobic digestion: solubiiizationlacid fermentation device (vertical mechanical agitator)> ~ Amount of a mixture of food waste, cut grass from river beds, and concentrated sludge introduced into a solubilization/acid fermentation device 3 m 3 /day (slurry TS concentration 10%) - TS ratio of fod waste and cut grass from river beds against the 'S of concentratedsludge 19% - HRT 2davs - Effective volume 6 in 3 -Water temperature 45*C <Anaerobi Dicgestion: AnaerobilDigestion Device (vertical mechanical agitator)> Amount ofsludge introduced to anaerbic digestion device 13.5 n 3 /day -HRT 14. days - Effective voluIne 200 n - Water temperature 37C <Plocculation step of anaerobicallydigested-sludge> - Slit-type concentrator (screen slit width 1.0 mm) - Amount of sludge separation effluent to be mixed 1 0.5 m/day (M alkalinity 690mg -27 CaCO 3 /L) Amount of biological odor control device waste liquid to be mixed 3.5 u/day (M alkalinity 1250 mg/L) Injection rate of cationie-polymer floceulant (mean molecular weight 3,000,000) 1.7% against SS) (Injection rate broken down:injection rate at the primary stage flocculation tank - 3%, injection rate at the reflocculation tank -- 0.4%) <Dew atering machine> - Screw press dewatering machine <Power genera tor> - Miero gas turbine power generator <Treatment Result> - Anaerobicallydigested-sludge characteristics (IS concentration 3'9%, VTS 68%, S S concentration 3.0%, M alkalinity 8900 mg CaCO3/1, coarse suspended solids content 167% (rate against SS)) Biogas generation amount 570 mday (NIP) - Methane gas generation amount 365 n/day ONP) - Methane gas concentration 64% - Methane gas generation rate 0.37 n/introduction kg VTS (NTP) - Sioxan D5 concentration in biogas 2.3 mgn/m Power production 686 kwh/dav Dewatered cake produced 2.1 ti/day (water content 77w%) Wastewater 37. m/day [0086] As seen above, it is shown that the present invention enables stable production of high quality biogas by the anaerobic treatment of sludge and organic waste using a greatly downsized anaerobic digestion device, and also enable biogas power generation. Conmpared to the conventional treatment method at an HRT of 20 to 30 days required an anaerobic digestion tank of 630 to 945 i the anaerobi digestion device of the present invention is - 28 206 mi so an anaerobic treatment is possible with a system having a anaerobic tank size that is 1/3 to 1/4 the conventional size. Further the generated anaerobically-digested-sludge can be flocculated and dewatered easily at a iov cost, and the dewatered cake water content obtained was77%, which is low compared to the conventonal rate of about 82% (Table 4), and the external appearance did not differ from conventional products, no unpleasant odor existed, and the cake was sanitary [0087 (Example 4] Similarly to Example 3, anaerobic treatment was performed on sewage sludge, and food waste (pomace of oranges for juice) in a sewage treatment plant based on Figure 5 Using a mixed sludge of primary settled concentrated sludge from gravity concentration and excess sludge as the sewage sludgeudge concentration was performed. The anaerobic digestion was performed at a mixture ratio of the solids of sewage sludge and the orange pomace at approximately equal amounts. [0088] <Treatment Corndition> - Sewage sludge amount (mixed sludge of primary settled sludge and excess sludge) 35 mJday (primary settled sludge: TS concentration 3.88%, excess sludge: TS concentration 0.93%, mixed sludge: TS concentration L39%) - Introduced food waste 4.0 tday (TS concentration 12%) Biomass storage tank 3 mx2 tanks <Pretreatment solid-liquid separator (for mixed sludge from the sewage)> Slit-type concentrator (screen slit width 1.0 mm, equipped wit a back pressure plate) - Amount Af injection of cationic polymer focculant (mean molecular weight 3,000.000, concentration of solution 2,0 g/L) 0.95 n 3 /day - Polymer flocculant injection rate 0.44 %(againstSS) - amount of concentrated sludge 6.2 t/day (T S concentration 7,5%) - amount of separation effluent 298 nrJday (SS concentration 230 mg/L) - SS recovery rate 98% <Solubiization/acid fermentation device of food waste 29 -9 6.0 m x, tank, vertical mechanical agitator, heated at 37 0 C TS ratio of food waste against the TS of concentrated sludge - 102% <Anaerobic Digestion Device (vertical mechanical agitator)> - Amount of sludge introduced to anaerobic digestion device 10.2 idav HRT 191 days - Effective volume 200 m 3 - Water temperature 3 7 0 C <Focculation step of anaerobicaliy-digested-sludge> = Slit-type concentrator (screen slit width 1 .0 mm)| Amount of sludge separation effluent to be mixed 2.0 m/day (M alkalnity 320 mg CaCO 3 /L) ~ Injection 'ate of cationic-polymer flocculant (mean molecular weight 3,000,000) --- 1% (against SS) -Flocculant injection step -- one <)ewatering machine> - Screw press dewatering machine <Power generator> - Micro gas turbine power generator <Treatment Result> ~Anaerobically-digested-sludge characteristics (IS concentration 3.8%, VTS 70%, SS concentration 32%, MA alkalinity 4490 mg CaCO/Lcoarse suspended solids content 12 1% (rate against SS)) - Biogas generation amount 591 mday (NTP) - Methane gas generation amount 349 m/day (NTP) - Methane gas concentration 59% - Methane gas generation rate 0.38 miintroduction kg TS (NI - Siloxan D5 concentration in biogas 1.2 mg/in 3 -30 -Power production 656 kwh/day - Dewatered cake produced 16tday (water content 78%) -Wastewater 41.5 m 3 /day [0089] As seen above, the sewage sludge concentration of the present invention enables efficient concentration treatment to a TS concentration of 7.5% against a mixed sludge (TS concentration 139%) of primary concentration sludge, on which only gravity concentratin and no nchanical concentration was performed and excess sludge, and various mechanical concentration facilities conventionaly used in large numbers can be eliminated. Further, the generated anaerobically-digested-sudge can be floceuated and dewatered easily at a low cost as in Example 3, and the dewatered cake water content stained was 78% which is low compared to the eon 'entional rate. [0090] [Example 5] The efficient use of waste liquid and dewatered cake produced in Examples 3 and 4 was considered, The separation effluent produced by the solid-liquid separation of sewage sludge in a pretercatment step in the present invention and the dewatered separation effluent of the dewatering step were subjected to phosphorous recovery, and the dewatered cake produced through the dewatering step of the concentrated anacrobicaliy-digested-sludge was composted. [0091] <Treatment Condition (1) Phosphorous recovery from solidliquid separation waste liquid of sludge (MAP method) - pH 8.3 and Mg concentration of 30 mg/ or higher at reaction time Itank reactor (reaction part: diameter 35 caheight 2.2 m, settling part: diameter 80 cmxheight 1.8 m, seed crystal of paticle size about 0.4 to 1 . mm is filled in advance) - Phosphorous volume load 20 kg-P/m 3 day (2) Conmposting of dcvwate ed cake - Test equipment for composting 15 n (high speed composting vertical fermentation tank) - water adjustment of dewatered sludge: sludge is mechanically dried to a water content of 45 to 55% -31 - No addition of sub-material - Aeration speed during composting 0.5 nt minutes G-reatment Result> [0092) [Table 6] 'fable 6 Phosphorous Recovecry Example 3 Example 4 Pretreatment Dewatering Pretreatment Dewatering s t ep step step step T-P Raw water (mg/L) 162 520 73 286 'Treatment water ng/I) 11 31 6.6 14 Phosphorous recovery rate (%) 93 94 &1 95 ......................................... ................. ...... [0093] [ Fable 7] Table 7Product Compost Characteristics <Comprative Data compost of Example T <Example 4 bnesophie methane fermented sludge of nWte %_ -63 65 629 H QG)4 a4 2t ---- - _ _ ---- (-w-------t........).. jPNaan 6 3&86 8 .arbon...... --------- . ...wto3l 6 .. tr...n...........-.- ----w----- 8 ....... sail (___ wt%) 100 0 04 0 -7 cnductivity-- ----------- < n 700 10 0 .0... Ma~~.............. oxd (.n.nsi.. -w% 0--075 -- adiunm (m'~) 09 09 __ :seni mgq 6 M -- - -7-7----------- ......... 00.7----- ~~Le....d ..... .....k LS.----------- ----- Copper n.-- -4...0 400711: - C hrom ium .... k. 60 7 6 [0094] As shown above, the wsaste liquid produced in Examples 3 and 4 of the present invention is subjected to phosphorous recovery and the dewxatered cake can be composted, -32 and the quality does not substantially differ from conventional products (the compost characteristics of mid-temperature methanefermented sludge from raw garbage are listed as comparative examples). The decomposition rate of organic matters in composting is 24% in the sludge of Example 3 and 28% in Example 4. Note that the high level heat generation of dewatered cake is 17 M/kg-dry for the sludge of Example 3, and 17.3 Mi/kg-dry for the sludge of Example 4, so they are of qualities that allow efficient usetas sludge fuel after the dewatered sludge is mechanically dried (the quality standard of fuelated substances (granulated/dried matter) is set at a calorific potetial of 4000 kal/kg or higher (16.7 M/kg or higher). REFERENCE SIGNS LIST [0095] 1 ... sludge, 2. storage tank, 3. occulation tank, 4... floccuiant, 5. focculated sludge, 6 . pretreatment sludge concentration tank, 7. concentrated sludge, .. digested sludge, 8...separation effluent 9, 9anaerobic digestion tank, 9a. solubilizationiacid fermentation treatment tank, 10.. biogass, l l..anaerobicallytdigested-sludge, 12..digested sludge flocculation device, .2asludge flocculation tank, W.. reconcentrated, flocculated sludge preparation device, 12c flocculatedd sludge, 12d concentrate, flocculated sludge, 14A. flocculated sludge separation/oncentration device, 15..flocculated digested-sludge, 13, 13a, 13b..flocculant, 14.. .separation effluent, 15... flocculated digested-sludge, 16. dewatering device, 17.. separation effluent, 18 .. dewatered cake, 19.. .biologically treated water, 20... organic waste liquid or waste matter, 21. biomass storage tank, 101.biogas tank 102.., gas-using facility, 103.. -surplus gas combustion facility 104-.wastewater treatment plant.

Claims

1. An anaerobic treatment process comprising: a pretreatment step for subjecting a flocculated sludge to a solid-liquid separation into concentrated sludge at a sludge concentration of 4 to 12 wt% and a separation effluent, wherein the flocculated sludge was prepared by adding a flocculant to a sludge; an anaerobic digestion step for anaerobically digesting the concentrated sludge and recovering biogas; a step for preparing a flocculated digested-sludge by mixing a flocculant and at least one of the separation effluent and water with an anaerobically-digested-sludge prepared in the anaerobic digestion step; and a step of dewatering a concentrated digested-sludge that was obtained by performing solid-liquid separation on the flocculated digested-sludge.

2. The method according to Claim 1, wherein the sludge is at least one of a primary settled sludge from a primary settling tank and an excess sludge from a final settling tank of a wastewater treatment plant.

3. The method according to Claim I or 2, wherein the flocculated sludge is prepared by using 0.2 to 1.0% of flocculant against SS of sludge.

4. The method according to any one of Claims I to 3, wherein the anaerobic digestion step comprises: a primary digestion step in which the concentrated sludge is subjected to solubilization and acid fermentation treatment at a treatment temperature of 30 to 60'C and HRT of I to 3 days; and a methane fermentation step for preparing the anaerobically-digested-sludge by subjecting the digested-sludge treated in the primary digestion step to a methane fermentation treatment.

5. The method according to Claim 4, wherein the methane fermentation step is characterized by a treatment temperature of 30 to 60'C and HRT of 12 to 20 days, and by -34 preparing the anaerobically-digested-sludge to have a coarse suspended solids content of 3 to 20% against SS.

6. The method according to any one of Claims 1 to 5, wherein an organic waste liquid or waste matter introduced from outside is adjusted to a slurry TS concentration of 1 to 15%, sent to the anaerobic digestion step, and subjected to anaerobic digestion at a mixture condition that provides a slurry TS ratio of 120% against a TS of the concentrated sludge.

7. The method according to any one of Claims 1 to 6, wherein the concentrated digested-sludge is prepared by performing a flocculant injection step at least twice, from a group of steps comprising a flocculant injection step and a subsequent solid-liquid separation step.

8. An anaerobic treatment apparatus comprising: a flocculation tank for preparing a flocculated sludge by adding a flocculant to sludge; a pretreatment sludge concentration device for subjecting a flocculated sludge to a solid-liquid separation into a concentrated sludge having a sludge concentration of 4 to 12 wt% and a separation effluent; an anaerobic digestion device for anaerobically digesting the concentrated sludge and recovering biogas; a digested-sludge flocculation device for preparing a flocculated digested-sludge by mixing a flocculant and at least one of the separation effluent and water with an anaerobically-digested-sludge prepared by the anaerobic digestion device; and a device for dewatering a concentrated digested-sludge that was obtained by subjection the flocculated digested-sludge to a solid-liquid separation.

9. The apparatus according to Claim 8 further comprising a sludge storage device for storing sludge, in which the sludge is at least one of a primary settled sludge from a primary settling tank and an excess sludge from a final settling tank of a wastewater treatment plant.

10. The apparatus of Claim 9 further comprising a system for supplying a flocculant to sludge discharged from the sludge storage device and a piping for delivering sludge. -35

11. The apparatus according to Claim 9 or 10, wherein the anaerobic digestion device comprises a device for performing solubilization and acid fermentation treatment on the concentrated sludge and a device for performing methane fermentation treatment on the digested-sludge treated in the device for performing solubilization and acid fermentation treatment.

12. The apparatus according to Claim 11, wherein a treatment temperature of the acid fermentation tank and the methane fermentation tank is 30 to 60*C.

13. The apparatus according to any one of Claims 8 to 12, wherein a device for preparing the concentrated digested-sludge comprises a sludge flocculation treatment device for preparing a flocculated sludge with the flocculant; a device for preparing a concentrated, flocculated sludge by performing solid-liquid separation on the flocculated sludge; and a device for preparing a reconcentrated, flocculated sludge from the concentrated, flocculated sludge with a flocculant.

14. The apparatus according to any one of Claims 11 to 13 further comprising an external biomass storage device that stores organic waste liquid or waste matter introduced from outside; a system and a piping for introducing biomass discharged from the external biomass storage device to at least one device selected from a group of the sludge storage device, a device for solubilization and acid fermentation treatment, and a methane fermentation device.