Advanced treatment system for municipal sludge wastewater

Abstract

A municipal sludge wastewater advanced treatment system is characterized in that a grating well is communicated with a comprehensive adjusting tank, the comprehensive adjusting tank is communicated with a high-precision self-cleaning filter, the high-precision self-cleaning filter is communicated with a pH adjusting reaction tank, the pH adjusting reaction tank is communicated with a coagulation reaction tank, and the coagulation reaction tank is communicated with a flocculation reaction tank; the flocculation reaction tank is communicated with the sedimentation tank, the sedimentation tank is communicated with the intermediate water tank, the intermediate water tank is communicated with the pulse water distributor, the pulse water distributor is communicated with the hydrolysis acidification tank, the hydrolysis acidification tank is communicated with the two-stage AO tank, the two-stage AO tank is communicated with the tubular ultrafiltration membrane, and the tubular ultrafiltration membrane is communicated with the clean water tank. The device is simple in structure and scientific and reasonable in design, municipal sludge is treated by combining high-precision self-cleaning filtration, pH regulation, coagulating sedimentation, hydrolytic acidification, two-stage AO biochemical treatment and a tubular ultrafiltration membrane, the operation cost of the system is reduced to the maximum extent, the treatment effect is good, the efficiency is high, and good social and economic benefits are achieved.

Description

TECHNICAL FIELD

[0001] The utility model relates to the field of sewage treatment, especially a municipal sludge wastewater advanced treatment system. BACKGROUND

[0002] With the development of urban industrialization and the construction of large-scale urban sewage treatment plants, the resource utilization of sludge in urban sewage plants is increasingly urgent. At present, most cities co-combust municipal sludge with household garbage after deep dewatering to generate electricity, maximizing the utilization of sludge resources. However, the wastewater generated by deep dewatering of municipal sludge still does not meet the discharge standard and needs to be treated before discharge.

[0003] To pursue a higher dewatering rate, a large amount of modified reagent is often added to destroy the sludge cell structure during the deep treatment of municipal sludge. Through mechanical extrusion and drying equipment, the water content of sludge is reduced so that it can enter the incinerator for incineration. The wastewater generated during dewatering and drying often contains a large amount of reagent. This wastewater has high suspended particles, high molecular polymers and other refractory substances, and poor biodegradability, making it difficult to treat.

[0004] Currently, the wastewater treatment processes for deep treatment of municipal sludge include "coagulation", "biochemical method", "electrocatalytic oxidation", and "Fenton advanced oxidation process". The coagulation method has general treatment effect and is not sufficient to meet the discharge standard, requiring deep treatment. The electrocatalytic oxidation method and the Fenton advanced oxidation method have good effect, but their energy consumption and operating cost are high, which is not the optimal choice. The biochemical method has limitations, and the single biochemical method has low treatment efficiency. Therefore, further improvement and innovation are needed for the existing systems for treating municipal sludge wastewater, but so far there has been no relevant public report. SUMMARY

[0005] In view of the above situation, to overcome the defects of the prior art, the purpose of the utility model is to provide a municipal sludge wastewater advanced treatment system, which can effectively solve the problems of high treatment cost, low treatment efficiency and failure to meet the discharge requirements of the existing treatment systems for municipal sludge wastewater.

[0006] In order to achieve the above object, the utility model solves technical scheme, a kind of municipal sludge wastewater advanced treatment system, including grating well, comprehensive regulating tank and sedimentation tank, the grating well effluent outlet is connected with the water inlet of comprehensive regulating tank by pipeline, the water outlet of comprehensive regulating tank is connected with the water inlet of high-precision self-cleaning filter by pipeline, the water outlet of high-precision self-cleaning filter is connected with the water inlet of pH adjustment reaction tank by pipeline, the water outlet of pH adjustment reaction tank is connected with the water inlet of coagulation reaction tank by pipeline, the water outlet of coagulation reaction tank is connected with the water inlet of flocculation reaction tank by pipeline, the water outlet of flocculation reaction tank is connected with the water inlet of sedimentation tank by pipeline, the water outlet of sedimentation tank is connected with the water inlet of intermediate water pool by pipeline, the water outlet of intermediate water pool is connected with the water inlet of pulse water distributor by pipeline, the water outlet of pulse water distributor is connected with the water inlet of hydrolysis acidification tank by pipeline, the water outlet of hydrolysis acidification tank is connected with the water inlet of two-stage AO pool by pipeline, the water outlet of two-stage AO pool is connected with the water inlet of tubular ultrafiltration membrane by pipeline, the water outlet of tubular ultrafiltration membrane is connected with the water inlet of clean water pool by pipeline.

[0007] The utility model discloses scientific and reasonable design, adopt " high-precision self-cleaning filter + pH adjustment + coagulation precipitation + hydrolysis acidification + two-stage AO biochemical + tubular ultrafiltration membrane " combination processing municipal sludge advanced treatment wastewater, maximum degree reduces system operating cost, and treatment effect is good, and efficiency is high, and there is good social and economic benefits. BRIEF DESCRIPTION OF DRAWINGS

[0008] Figure 1 It is the structure connection frame diagram of the utility model. DETAILED DESCRIPTION

[0009] The specific embodiment of the utility model is explained in detail in the following in combination with the drawings and specific conditions.

[0010] In combination with the drawings, a municipal sludge wastewater advanced treatment system is provided, which comprises a grid well, a comprehensive conditioning tank and a sedimentation tank. The water outlet of the grid well 1 is connected to the water inlet of the comprehensive conditioning tank 2 through a pipeline. The water outlet of the comprehensive conditioning tank 2 is connected to the water inlet of a high-precision self-cleaning filter 3 through a pipeline. The water outlet of the high-precision self-cleaning filter 3 is connected to the water inlet of a pH adjusting reaction tank 4 through a pipeline. The water outlet of the pH adjusting reaction tank 4 is connected to the water inlet of a coagulation reaction tank 5 through a pipeline. The water outlet of the coagulation reaction tank 5 is connected to the water inlet of a flocculation reaction tank 6 through a pipeline. The water outlet of the flocculation reaction tank 6 is connected to the water inlet of the sedimentation tank 7 through a pipeline. The water outlet of the sedimentation tank 7 is connected to the water inlet of an intermediate tank 10 through a pipeline. The water outlet of the intermediate tank 10 is connected to the water inlet of a pulse water distributor 11 through a pipeline. The water outlet of the pulse water distributor 11 is connected to the water inlet of a hydrolysis acidification tank 12 through a pipeline. The water outlet of the hydrolysis acidification tank 12 is connected to the water inlet of a two-stage AO tank through a pipeline. The water outlet of the two-stage AO tank is connected to the water inlet of a tubular ultrafiltration membrane 15 through a pipeline. The water outlet of the tubular ultrafiltration membrane 15 is connected to the water inlet of a clear water tank 16 through a pipeline.

[0011] In order to ensure better implementation effect, the two-stage AO tank comprises a first anoxic tank 13, a first aerobic tank 14, a second anoxic tank 131 and a second aerobic tank 141 which are connected in sequence through pipelines. The water outlet of the hydrolysis acidification tank 12 is connected to the water inlet of the first anoxic tank 13 through a pipeline. The water outlet of the second aerobic tank 141 is connected to the water inlet of the tubular ultrafiltration membrane 15 through a pipeline. The nitrification liquid outlets of the first aerobic tank 14 and the second aerobic tank 141 are respectively returned to the first anoxic tank 13 and the second anoxic tank 131 through pipelines.

[0012] The comprehensive conditioning tank 2, the pH adjusting reaction tank 4, the first aerobic tank 14 and the second aerobic tank 141 are all provided with on-line pH meters. The high-precision self-cleaning filter 3 is provided with a differential pressure sensor. The first anoxic tank 13 and the second anoxic tank 131 are both provided with ORP analyzers and temperature controllers. The first aerobic tank 14 and the second aerobic tank 141 are both provided with DO analyzers. The tubular ultrafiltration membrane 15 is provided with a pressure gauge.

[0013] The sedimentation outlet of the sedimentation tank 7 is connected to the inlet of a sludge concentration tank 8 through a pipeline. The outlet of the sludge concentration tank 8 is connected to the inlet of a stacked screw dewatering machine 9 through a pipeline. The water outlet of the stacked screw dewatering machine 9 is connected to the water inlet of the grid well 1 through a pipeline.

[0014] The sludge outlets of the tubular ultrafiltration membrane 15 are respectively connected to the inlets of the first anoxic tank 13 and the sedimentation tank 7 through pipelines.

[0015] The pH adjusting reaction tank 4, the coagulation reaction tank 5 and the flocculation reaction tank 6 are all provided with deceleration mixers.

[0016] The stacked screw dewatering machine 9 is a 301 type stacked screw dewatering machine.

[0017] The working condition of the utility model is:

[0018] S1, adjust pH: the municipal sludge deep treatment wastewater is collected and enters the comprehensive adjusting pool 2 through the grid well 1 to carry out comprehensive adjustment, and the pH is 6~9 by adding acid and alkali reagent to the comprehensive adjusting pool 2, then the adjusted wastewater is pumped into high-precision self-cleaning filter 3 to carry out filtration, high-precision self-cleaning filter 3 adopts 10~300 mesh screen to carry out physical interception, the filter has automatic cleaning function, and is automatically cleaned by pressure difference sensor, and the equipment adopts automatic program control and does not need manual cleaning;

[0019] S2, the filtered wastewater enters the pH adjusting reaction tank 4 and reacts for 5~10 min, the speed of the speed reducer stirrer is 30~50 r / min, the pH is adjusted to 7~8.5 by adding acid / alkali, the wastewater after adjusting pH enters the coagulation reaction tank 5, the reaction time is 5~15 min, the speed of the speed reducer stirrer is 30~50 r / min, the polyaluminum chloride (PAC) adding amount is 10~50 mg / l;Then the wastewater enters the flocculation reaction tank 6, the reaction time is 5~12 min, the speed of the speed reducer stirrer is 10~25 r / min, the polyacrylamide (PAM) adding amount is 2~5 mg / l, and after sufficient reaction, it enters the sedimentation tank 7 to separate mud and water, and the supernatant flows into the intermediate water tank 10;

[0020] S3, the intermediate water tank 10 lifts the pump to pump the wastewater to the pulse water distributor 11, and uniformly distributes the water to the bottom of the acidification tank 12 through the pulse water distributor 11, under anaerobic conditions, the high-efficiency anaerobic bacteria hydrolyze and acidify the refractory substances in the wastewater, the biodegradability (B / C) of the acidified wastewater is improved, and the B / C reaches more than 0.3;

[0021] S4, the effluent of the hydrolysis acidification tank 12 flows into the aerobic biochemical treatment section, the aerobic treatment process adopts two-stage AO process to remove nitrogen, and biological denitrification is carried out through the nitrification and denitrification of nitrifying bacteria and denitrifying bacteria, the first aerobic tank 14 and the second aerobic tank 141 in the two-stage AO process are provided with on-line pH meter and DO (dissolved oxygen) analyzer, the first anoxic tank 13 and the second anoxic tank 131 are provided with ORP (oxidation-reduction potential instrument) analyzer and temperature controller, and real-time monitoring is carried out, the value of the ORP analyzer is controlled between +50~-50 mV, the value of the on-line pH meter is controlled between 7~8, the dissolved oxygen of the second aerobic tank 141 is controlled between 2~4 mg / l, and the temperature of the temperature controller is controlled between 20~35 DEG C;

[0022] S5. The effluent from the two-stage AO process enters the tubular ultrafiltration membrane 15 for sludge-water separation. The ultrafiltration uses an external tubular ultrafiltration membrane, which, compared to traditional MBRs, has a higher flux, can adapt to a wider range of sludge concentrations, and is easier to inspect and maintain, with a higher degree of automation. The flux of the external tubular ultrafiltration membrane is typically 50~120 L / (m².h), and it can adapt to sludge concentrations of 10~50 g / L. Its principle is to utilize the microporous filtration effect of the membrane to retain activated sludge, increasing the activated sludge concentration, thereby improving the removal efficiency of pollutants (CODcr, BOD, etc.) and maximizing the efficiency of biological treatment. Furthermore, since the effluent is filtered through the membrane, a secondary sedimentation tank and subsequent filtration facilities are eliminated, reducing the footprint of the wastewater treatment facility and shortening the treatment process.

[0023] S6. The backwash water from the high-precision self-cleaning filter 3, the sludge from the sedimentation tank 7, and a portion of the sludge from the tubular ultrafiltration membrane 15 enter the sludge thickening tank 8 for thickening. A high molecular weight flocculant with a molecular weight greater than 12 million is added to the sludge thickening tank 8 and, after adjustment, is pumped into the screw press dewatering machine 9 for dewatering. The dewatered sludge is pumped to the municipal sludge deep treatment workshop for deep treatment, while the filtrate is backflowed to the bar screen well 1 for recycling.

[0024] The present invention is illustrated in the following embodiments.

[0025] A municipal waste incineration project uses municipal solid waste and municipal sludge as raw materials for co-incineration. The plant is equipped with a treatment production line that can process 300 tons of municipal sludge (80% moisture content) per day. Wastewater sources include wastewater from the vertical high-pressure plate and frame extrusion of the sludge treatment production line, drying wastewater from the disc sludge drying equipment, workshop floor washing water, and domestic sewage from the plant area, with a daily wastewater volume of 200 tons / day.

[0026] After mixing, the water quality in the equalization tank is as follows:

[0027] CODcr=3500mg / l, BOD5=1000mg / l, NH3-N=400m / l, TN=500mg / l, TP=10mg / l, SS=1200mg / l, pH=4~6 (dimensionless).

[0028] The discharge standards are as follows, based on the local municipal wastewater treatment plant's effluent acceptance standards:

[0029] CODcr=400mg / l, BOD5=150mg / l, NH3-N=30m / l, TN=45mg / l, TP=6mg / l, SS=150mg / l, pH=6.5~9.5 (dimensionless).

[0030] Using the municipal sludge wastewater deep treatment system of this application, the process route of this project is designed as follows: "bar → comprehensive regulation → high-precision self-cleaning filtration → pH adjustment → coagulation sedimentation → hydrolysis acidification → two-stage AO biochemical treatment → tubular ultrafiltration membrane → clear water tank → discharge in compliance with standards".

[0031] After the workshop wastewater is collected, it enters the sewage treatment plant's equalization tank through a screen well for comprehensive adjustment. The pH value is roughly adjusted to 6-9 by adding liquid alkali. Then, the adjusted wastewater is pumped into a high-precision self-cleaning filter for filtration. The high-precision self-cleaning filter uses a 10-300 mesh screen for physical interception. The filter has an automatic cleaning function, which is automatically cleaned by a differential pressure sensor. The equipment is automatically controlled by a program and does not require manual cleaning.

[0032] The filtered wastewater flows by gravity into the pH adjustment reaction tank, where the reaction time is 5 minutes and the speed of the agitator is 50 rpm. The pH value is adjusted to 7-8.5 by adding liquid alkali. After pH adjustment, the wastewater flows into the coagulation reaction tank, where the reaction time is 5 minutes and the speed of the agitator is 50 rpm. The dosage of polyaluminum chloride (PAC) is 30 mg / L. The flocculation reaction tank has a reaction time of 10 minutes and a speed of the agitator is 20 rpm. The dosage of polyacrylamide (PAM) is 3 mg / L. After the reaction is complete, the wastewater flows into the sedimentation tank for sludge-water separation. The supernatant flows by gravity into the intermediate water tank.

[0033] The intermediate water tank lift pump pumps the wastewater to the hydrolysis acidification unit. The water is then evenly distributed to the activated sludge bed at the bottom of the acidification tank by the pulse water distributor. Under anaerobic conditions, highly efficient anaerobic bacteria hydrolyze and acidify the recalcitrant substances in the wastewater. The biodegradability (B / C) of the acidified wastewater is improved, reaching a B / C ratio of over 0.3.

[0034] After high-precision self-cleaning filtration, pH adjustment, coagulation sedimentation, and hydrolysis acidification, the effluent quality of the hydrolysis acidification tank is as follows: CODcr=2500mg / l, BOD5=800mg / l, NH3-N=400mg / l, TN=500mg / l, TP=3mg / l, SS=200mg / l, pH=7~8 (dimensionless). The removal rates are as follows: CODcr=28.5%, BOD5=20%, TP=70%, SS=83.3%, B / C=0.32, and biodegradability is significantly improved.

[0035] The effluent from the hydrolysis acidification tank flows by gravity into the aerobic biological treatment section. The aerobic treatment process adopts a two-stage AO process for denitrification, which is carried out through nitrification / denitrification by nitrifying and denitrifying bacteria. The two-stage AO process is equipped with a variety of instruments for real-time monitoring. The oxidation-reduction potential (ORP) meter value is controlled between +50 and -50 mV, the online pH count value is controlled between 7 and 8, the dissolved oxygen in the second aerobic tank is controlled below 3 mg / L, the temperature is not lower than 20℃, and the normal operating temperature is 20~30℃.

[0036] The effluent from the two-stage AO process enters an ultrafiltration system for sludge-water separation. The ultrafiltration uses an external tubular ultrafiltration membrane, which, compared to traditional MBRs, has a higher flux, can adapt to a wider range of sludge concentrations, and is easier to inspect and maintain, with a higher degree of automation. Its principle is to utilize the microporous filtration effect of the membrane to retain activated sludge, increasing the activated sludge concentration and thus improving the removal efficiency of pollutants (CODcr, BOD, etc.), maximizing the efficiency of biological treatment. Furthermore, because the effluent is filtered through a membrane, a secondary sedimentation tank and subsequent filtration facilities are eliminated, reducing the footprint of the wastewater treatment facility and shortening the treatment process.

[0037] The project is designed with an external tubular ultrafiltration membrane flux of 55 L / (m².h) and a sludge concentration of 25 g / L. The ultrafiltration process is fully automated and requires no manual intervention. The ultrafiltration feed pump has a flow rate of 83 m³ / h and a head of 20 m, while the ultrafiltration circulation pump has a flow rate of 264 m³ / h and a head of 50 m. The product water flow rate is 8.5 m³ / h, and the membrane system operates at a pressure of 5-6 bar. One ultrafiltration membrane module is used as a backup, and a chemical cleaning system is also included.

[0038] After passing through two stages of AO and ultrafiltration membrane separation units, the final effluent quality is as follows: CODcr=250mg / l, BOD5=30mg / l, NH3-N=15mg / l, TN=36mg / l, TP=1.3mg / l, SS=0.5mg / l, pH=7~8 (dimensionless). The removal rates are as follows: CODcr=90%, BOD5=96.3%, NH3-N=96.3%, TN=92.8%, TP=50%, and SS=99.7%. The effluent quality meets the municipal wastewater treatment plant discharge standards and can be stably discharged in compliance with the standards.

[0039] The backwash water from the precision self-cleaning filter, the sludge from the sedimentation tank, and a portion of the sludge from the tubular ultrafiltration membrane are concentrated in the sludge thickening tank. A high molecular weight flocculant, using cationic polyacrylamide with a molecular weight of 12 million, is added as a conditioner. After conditioning, the sludge is pumped into a screw press dewatering machine for dewatering. The project is equipped with a 301-type screw press dewatering machine. After dewatering, the sludge has a moisture content of about 80-85%. The dewatered sludge is pumped to the municipal sludge deep treatment workshop for deep treatment using a screw pump, while the filtrate is backflowed to the bar screen well for recycling.

[0040] This utility model is scientifically and rationally designed, and has the following advantages compared with the prior art:

[0041] 1. To address the problem of high suspended solids in wastewater, this utility model employs a high-precision self-cleaning filter to intercept solid particles. Solid particles are trapped inside the filter using a high-precision 10-300 mesh screen, and then a coagulation method is used for polymer flocculation and sedimentation to solve the problem of high suspended solids in wastewater. The backwashing program is automatically activated by changes in pressure difference, which greatly saves labor costs.

[0042] 2. For recalcitrant substances in wastewater, this utility model adopts an improved biochemical method for biochemical treatment. It uses domesticated microorganisms for biochemical degradation, minimizing operating costs. The two-stage AO biochemical treatment process uses high-precision analytical instruments (pH, ORP, DO, temperature) to monitor the biochemical reaction status in real time, making the biochemical treatment visible and controllable. The changes in instrument parameters provide an operational basis for the biochemical treatment.

[0043] 3. The treatment end uses an external tubular ultrafiltration membrane for sludge-water separation, which increases the sludge concentration in the biological treatment tank while maximizing the efficiency of biological treatment. Most importantly, it saves the traditional secondary sedimentation tank and subsequent filtration facilities, reduces the footprint of the sewage treatment facility, shortens the treatment process, and features fully automated control operation, saving labor costs. It has good treatment effect, high efficiency, and good social and economic benefits.

[0044] It should be noted that all the above-mentioned components are existing technologies and commercially available products. The contribution of this utility model lies in the scientific design and layout of these known components, effectively solving the defects of existing technologies and meeting production needs. It should also be pointed out that the above are merely preferred embodiments of this utility model and are not intended to limit the utility model in any way. Any modifications or alterations made by those skilled in the art, without departing from the scope of the technical solution of this utility model, to create equivalent embodiments based on the disclosed technical content, shall fall within the protection scope of this utility model.

Claims

1. A municipal sludge wastewater deep treatment system, comprising a bar screen, a general equalization tank, and a sedimentation tank, characterized in that, The outlet of the grid well (1) is connected to the inlet of the integrated regulating tank (2) via a pipeline. The outlet of the integrated regulating tank (2) is connected to the inlet of the high-precision self-cleaning filter (3) via a pipeline. The outlet of the high-precision self-cleaning filter (3) is connected to the inlet of the pH adjusting reaction tank (4) via a pipeline. The outlet of the pH adjusting reaction tank (4) is connected to the inlet of the coagulation reaction tank (5) via a pipeline. The outlet of the coagulation reaction tank (5) is connected to the inlet of the flocculation reaction tank (6) via a pipeline. The outlet of the flocculation reaction tank (6) is connected to the sedimentation tank (7) via a pipeline. The inlet is connected to the outlet of the sedimentation tank (7) and the outlet of the intermediate water tank (10) are connected to the inlet of the intermediate water tank (10) via a pipe. The outlet of the intermediate water tank (10) is connected to the inlet of the pulse water distributor (11) via a pipe. The outlet of the pulse water distributor (11) is connected to the inlet of the hydrolysis acidification tank (12) via a pipe. The outlet of the hydrolysis acidification tank (12) is connected to the inlet of the two-stage AO tank via a pipe. The outlet of the two-stage AO tank is connected to the inlet of the tubular ultrafiltration membrane (15) via a pipe. The outlet of the tubular ultrafiltration membrane (15) is connected to the inlet of the clear water tank (16) via a pipe.

2. The municipal sludge wastewater deep treatment system according to claim 1, characterized in that, The two-stage AO tanks include a first anoxic tank (13), a first aerobic tank (14), a second anoxic tank (131), and a second aerobic tank (141) connected in sequence by pipes. The outlet of the hydrolysis acidification tank (12) is connected to the inlet of the first anoxic tank (13) by pipes, and the outlet of the second aerobic tank (141) is connected to the inlet of the tubular ultrafiltration membrane (15) by pipes. The nitrified liquid outlets of the first aerobic tank (14) and the second aerobic tank (141) are respectively returned to the first anoxic tank (13) and the second anoxic tank (131) by pipes.

3. The municipal sludge wastewater deep treatment system according to claim 1, characterized in that, The integrated conditioning tank (2), pH conditioning reaction tank (4), first aerobic tank (14) and second aerobic tank (141) are all equipped with online pH meters, the high-precision self-cleaning filter (3) is equipped with a differential pressure sensor, the first anoxic tank (13) and the second anoxic tank (131) are both equipped with ORP analyzers and temperature controllers, the first aerobic tank (14) and the second aerobic tank (141) are both equipped with DO analyzers, and the tubular ultrafiltration membrane (15) is equipped with a pressure gauge.

4. The municipal sludge wastewater deep treatment system according to claim 1, characterized in that, The sedimentation outlet of the sedimentation tank (7) is connected to the inlet of the sludge thickening tank (8) via a pipeline. The outlet of the sludge thickening tank (8) is connected to the inlet of the screw press dewatering machine (9) via a pipeline. The outlet of the screw press dewatering machine (9) is connected to the inlet of the bar screen well (1) via a pipeline.

5. The municipal sludge wastewater deep treatment system according to claim 1, characterized in that, The sludge outlet of the tubular ultrafiltration membrane (15) is connected to the inlet of the first anoxic tank (13) and the sedimentation tank (7) via pipelines.

6. The municipal sludge wastewater deep treatment system according to claim 1, characterized in that, The pH adjustment reaction tank (4), coagulation reaction tank (5) and flocculation reaction tank (6) are all equipped with a speed reducer mixer.

7. The municipal sludge wastewater deep treatment system according to claim 1, characterized in that, The aforementioned screw press dewatering machine (9) is a 301 type screw press dewatering machine.

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