Treatment process for scaling of external water delivery pipe and pump body of common and auxiliary chromium-containing wastewater treatment system

Abstract

The invention discloses a treatment process for scaling of an external water delivery pipe and a pump body of a public and auxiliary chromium-containing wastewater treatment system, which comprises the following steps of: dynamically controlling flocculation at a source, blocking filter-pressing overflow, and additionally arranging a return pipe between a monitoring tank and the external water delivery pipe, the waste water accounting for 20%-30% of the water yield of an outlet of the centrifugal pump of the monitoring tank flows back to the monitoring tank through a flow control valve, waste acid water containing nitric acid and hydrofluoric acid in the waste acid pool is introduced into the outer water conveying pipe to conduct back flushing on the outer water conveying pipe, and the waste water obtained after flushing flows back to the distribution pool to be treated. A whole-process cooperative treatment scheme with'source inducement control-process overflow blocking-tail end scaling removal 'as the core is formed, the problem of calcium sulfate scaling of an outer water conveying pipe and a pump body caused by clear liquid overflow of the acid-containing sedimentation tank is specially solved, and the method is suitable for operation and maintenance optimization of a high-calcium acid-containing wastewater treatment system.

Description

Technical Field

[0001] This invention relates to wastewater treatment processes in iron and steel smelting, and more particularly to a process for treating scale buildup on the external water supply pipes and pump bodies of a chromium-containing wastewater treatment system. Background Technology

[0002] The auxiliary chromium-containing wastewater treatment system includes a pipeline-connected waste acid purification and recovery system: waste acid tank, distribution tank, waste acid neutralization tank, sedimentation tank, filter press and monitoring tank. The auxiliary chromium-containing wastewater treatment process includes water collection and adjustment → reduction and sedimentation → flocculation and clarification → ultrafiltration (UF) → nanofiltration (NF) / reverse osmosis (RO) → reuse / discharge. In this process, calcium sulfate scaling on the external water supply pipe and the external water supply pump body is a common pain point that has long remained unresolved in the industry.

[0003] The core of chromium-containing wastewater treatment in public facilities is "Cr 6+ Reduction → Cr 3+ "Sedimentation" is a process that produces chromium compounds, which are a specific "pollution source" for pipe scaling. At the same time, due to the characteristics of wastewater and the addition of chemicals, the treatment process is also accompanied by the formation of scale such as calcium and magnesium salts (e.g., calcium sulfate) and silicates, which are common in ordinary industrial wastewater. When these scale layers are superimposed on the chromium scale layer, they further aggravate pipe blockage.

[0004] Currently, scaling control typically involves three aspects: optimizing process parameters (stabilizing pH, controlling flow rate), selecting suitable materials (corrosion-resistant coated pipes), and regular cleaning. However, existing treatment processes have significant limitations. 1. Lack of control over the source causes: The current method of treating chromium sludge and flocs in the flocculation and clarification process is "fixed dosage of flocculant". It is difficult to accurately match the dosage with water quality fluctuations. If the dosage is insufficient, the chromium sludge will not flocculate sufficiently, and the unsettled particles will enter the pipeline with the water flow. If the dosage is excessive, it will not only lead to an increase in wastewater COD, but also cause excessive organic matter to be adsorbed on the pipe wall to form an "organic adhesion layer", which will then adsorb Cr(OH)3 and calcium and magnesium salt particles. At the same time, excessive flocculant (PAC / PAM) will form "colloidal flocs" that are deposited in the pipeline. It is impossible to cut off the cause of scaling at the source.

[0005] 2. Overflow prevention failure in the filter press stage: Existing filter presses only focus on the single indicator of "filter cake moisture content" and do not optimize parameters in conjunction with the wastewater treatment capacity of the sedimentation tank. For example, when the filter press flow rate is fixed at 50 m³ / h, if the average daily wastewater volume reaches 350 m³, insufficient filtration efficiency will cause the sedimentation tank to overflow, and wastewater carrying high concentrations of ions will directly enter the subsequent pipelines, becoming a "direct driver" of scaling; some solutions increase the filtration flow rate, but the filter cake moisture content exceeds 45%, which actually increases the load on subsequent treatment.

[0006] 3. Inefficient end-point scaling removal: When scale buildup on pumps and pipes is severe, either manual disassembly and cleaning of the pipes / pumps is required, or the scale-resistant material must be replaced. Taking the applicant's 350m³ / day chromium-containing wastewater treatment system as an example, manual disassembly and cleaning needs to be carried out 80 times a year, with a cost of 1,788 yuan per instance; the cost of replacing pipes in a single batch reaches 630,000 yuan, and the annual maintenance cost is as high as 1,254,000 yuan.

[0007] Therefore, there is an urgent need to develop a process for treating scaling on the external water supply pipes and pumps of a public auxiliary chromium-containing wastewater treatment system that involves the entire process. Summary of the Invention

[0008] The purpose of this invention is to provide a treatment process for scaling on the external water supply pipe and pump body of a public auxiliary chromium-containing wastewater treatment system.

[0009] The technical solution to achieve the purpose of this invention is: a treatment process for scaling on the external water supply pipe and pump body of a public auxiliary chromium-containing wastewater treatment system. The public auxiliary chromium-containing wastewater treatment system includes a waste acid tank, a distribution tank, a waste acid neutralization tank, a sedimentation tank, a filter press, and a monitoring tank, all connected in sequence by pipelines. The monitoring tank is connected to an external water supply pipe, which is equipped with an inlet valve and an outlet valve. The treatment process includes the following steps: (1) Dynamic control of flocculants at the source: In the flocculation and clarification stage, when the surface area of ​​the sedimentation tank covered by foam is greater than 1 / 3 of the surface area of ​​the sedimentation tank, the amount of flocculant added is increased to 1.3-1.4 times the fixed amount of conventional flocculant added; when the surface area of ​​the sedimentation tank covered by foam is greater than or equal to 1 / 5 of the surface area of ​​the sedimentation tank and less than or equal to 1 / 3 of the surface area of ​​the sedimentation tank, the amount of flocculant added is increased to 0.9-1 times the fixed amount of conventional flocculant added; when the surface area of ​​the sedimentation tank covered by foam is less than 1 / 5 of the surface area of ​​the sedimentation tank, the amount of flocculant added is reduced to 0.7-0.8 times the fixed amount of conventional flocculant added. (2) Filter press overflow prevention: The filter press processing flow rate, pressing pressure and pressing time are comprehensively controlled. The filter press processing flow rate is controlled at ≥110m³ / h, the pressing pressure is controlled at ≥1.1Mpa, and the pressing time is controlled at 800-1300s. The upper limit of the filter press processing flow rate and the upper limit of the pressing pressure are limited to the state where the wastewater in the sedimentation tank does not need to overflow. (3) A return pipe is added between the monitoring tank and the external water supply pipe. A return pipe valve is installed on the return pipe. 20%-30% of the wastewater from the centrifugal pump outlet of the monitoring tank is returned to the monitoring tank through the return pipe valve. The flow velocity of the monitoring tank is controlled to be ≥0.3m / s so that the water in the tank remains in a dynamic spiral shape and crystallization is avoided due to water stagnation. (4) The waste acid water containing nitric acid and hydrofluoric acid in the waste acid tank is passed into the external water supply pipe for reverse flushing. The flushed waste water is returned to the distribution tank for treatment.

[0010] Furthermore, a sampling pipeline connected to the external water supply pipe is installed between the inlet valve and the outlet valve of the external water supply pipe. The sampling pipeline is adjacent to the outlet valve of the external water supply pipe. A first waste acid pipe connected to the waste acid tank is installed on the external water supply pipe between the inlet valve and the sampling pipeline. The first waste acid pipe is located close to the sampling pipeline. A second waste acid pipe connected to the distribution tank is installed between the inlet valve and the first waste acid pipe. A first valve is installed on the first waste acid pipe, and a second valve is installed on the second waste acid pipe. A sampling valve is installed on the sampling pipeline.

[0011] In existing technologies, solutions for scaling in wastewater treatment systems often focus on a single stage, failing to form a comprehensive treatment system encompassing "source control - process optimization - end-of-pipe protection." This leads to recurring scaling problems and fails to fundamentally reduce maintenance costs and environmental risks. The scaling treatment process for external water supply pipes and pumps in auxiliary chromium-containing wastewater treatment systems implemented in this invention is a comprehensive, synergistic treatment solution centered on "source cause control - process overflow prevention - end-of-pipe scaling removal." It specifically addresses the problem of calcium sulfate scaling in external water supply pipes and pumps caused by overflow of clear liquid from acidic sedimentation tanks. Specifically: 1. The dynamic floc control mechanism at the source enables "on-demand addition," which not only cuts off the "ion source" of scaling but also reduces the cost of chemicals and avoids waste, reducing flocculant consumption by 20% compared to existing technologies; 2. The filter press overflow blocking solution eliminates the need for wastewater to overflow from the sedimentation tank, thus blocking the "transport path" for scale formation. 3. Control the flow velocity in the monitoring tank: ≥0.3m / s to keep the water in the tank in a dynamic spiral shape and avoid crystallization caused by water stagnation; 4. The principle of using waste acid water containing nitric acid and hydrofluoric acid in the waste acid tank (i.e., APU wastewater tank) to backwash the external water supply pipe is as follows: The waste acid discharge process is continuous, and the liquid in the pipeline is fluid. The core descaling mechanism of HF includes: Step 1: Directional consumption of Ca 2+ HF reacts with CaSO4 to form CaF2 (a sparingly soluble substance), directly removing Ca from the system. 2+ This disrupts the calcium sulfate dissociation equilibrium, forcing the scale layer to continuously dissolve and replenish Ca. 2+ Step 2: Remove interfering products. Excess HF reacts with the H2SO4 produced in the reaction to generate HSO3F or HF gas. The gas escapes and carries away the SO4. 2- and H + This avoids product buildup that inhibits subsequent reactions, achieving deep descaling rather than surface treatment. Nitric acid plays a supporting role in enhancing the dissociation of HF by regulating its dissociation state: complete ionization of nitric acid releases a large amount of H₂.+ By inhibiting the hydrolysis of HF through the common ion effect, HF is made more easily dissociated into F. - Improve F - With Ca 2+ The binding efficiency. , at high concentrations of H + In the environment, some CaF2 will react with H + The reaction produces HF (CaF2+ 2H+). + → Ca 2+ + 2HF↑), after the HF gas escapes, Ca 2+ It can be used again with F in the system - The combination forms a "dissolution-reaction-escape" cycle, which accelerates the removal of scale and ultimately achieves "efficient and thorough removal of calcium sulfate scale." Furthermore, the products (such as CaF2 precipitate, HF gas, and soluble ions) can be treated through subsequent processes such as pressure filtration and degassing to avoid secondary pollution.

[0012] This invention can achieve the three-in-one goal of "scale prevention + scale removal + cost reduction", filling the gap in the lack of full-chain prevention and control in existing technologies, and is applicable to the operation and maintenance optimization of high-calcium acid wastewater treatment systems. Attached Figure Description

[0013] Figure 1 This is a schematic diagram of the chromium-containing wastewater treatment system for public utilities described in an embodiment of the present invention. Detailed Implementation

[0014] The preferred embodiment of the treatment process for scaling in the external water supply pipe and pump body of a public auxiliary chromium-containing wastewater treatment system of the present invention will be described in detail below.

[0015] Taking our company's daily average 350m³ acidic wastewater treatment system as an example, before treatment: half of the sedimentation tank was covered with scum, the pipe scaling rate was 30%, the pump body was cleaned an average of 7 times per month, and the annual maintenance cost was 1.254 million yuan. Example 1

[0016] A process for treating scaling on the external water supply pipe and pump body of a public auxiliary chromium-containing wastewater treatment system, wherein the public auxiliary chromium-containing wastewater treatment system includes a waste acid tank 1, a distribution tank 2, a waste acid neutralization tank 3, a sedimentation tank 4, a filter press 5, and a monitoring tank 6 connected in sequence by pipes; the monitoring tank 6 is connected to an external water supply pipe 10, the external water supply pipe 10 is equipped with an external water supply pipe inlet valve 101 and an external water supply pipe outlet valve 102, a return pipe 20 is added between the monitoring tank 6 and the external water supply pipe inlet valve 101, and a sampling pipeline 30 connected to the external water supply pipe 10 is installed between the external water supply pipe inlet valve 101 and the external water supply pipe outlet valve 102. The water outlet valve 102 of the external water supply pipe is adjacent to the water inlet valve 101 of the external water supply pipe and the sampling pipeline 30. A first waste acid pipe 40 connected to the waste acid tank 1 is installed on the external water supply pipe 10 between the water inlet valve 101 of the external water supply pipe and the sampling pipeline 30. The first waste acid pipe 40 is located close to the sampling pipeline 30. A second waste acid pipe 50 connected to the distribution tank 2 is installed between the water inlet valve 101 of the external water supply pipe and the first waste acid pipe 40. A first valve 401 is installed on the first waste acid pipe 40. A second valve 501 is installed on the second waste acid pipe 50. A sampling valve 301 is installed on the sampling pipeline 30. A return pipe valve 201 is installed on the return pipe 20.

[0017] Its treatment process includes the following steps: (1) Dynamic control of flocculants at the source: When the flocculants cover more than 1 / 3 of the surface area of ​​the sedimentation tank during the flocculation and clarification process, the amount of flocculant added is increased to 1.3 times the original amount. The amount of flocculant added is dynamically adjusted from 20 kg / h to 26 kg / h to ensure that the acid sludge is fully flocculated and to reduce ion residue. (2) Filter press overflow prevention: The filter press processing flow rate is controlled at 110 m³ / h, the pressing pressure is controlled at 1.1 MPa, the pressing time is controlled at 800 s, the filter cake moisture content is 38% (≤42%), the daily processing capacity is increased from 1100 m³ to 1300 m³, and the acid sedimentation tank clear liquid overflows zero. (3) The monitoring tank has a volume of 60 m³, a reflux ratio of 25% (12.5 m³ / h), a water flow velocity of 0.3 m / s, and no scale buildup after standing. (4) The waste acid water containing nitric acid and hydrofluoric acid in the waste acid tank is passed into the external water supply pipe for reverse flushing. The 150mm scale layer on the inner wall of the 600-meter pipe is completely removed, and the inner diameter of the pipe is restored to 100%. like Figure 1As shown, under normal conditions, the waste acid water in the waste acid tank 1 passes through the distribution tank 2, waste acid neutralization tank 3, sedimentation tank 4, filter press 5 and monitoring tank 6 in sequence via pipelines, and is finally discharged through the external water supply pipe 10. When the external water supply pipe becomes blocked, close the valve between the wastewater tank and the distribution tank, and the external water supply pipe outlet valve 102. Open the first valve 401 and the second valve 501 to flush and unclog the external water supply pipe 10 using the mixed acid in the waste acid tank 1. The flushed wastewater is then returned to the distribution tank 2. After treatment, close the waste acid pump in the waste acid tank, open the valve between the wastewater tank and the distribution tank, and the external water supply pipe inlet valve 101. Use the treated wastewater in the monitoring tank 6 to flush the external water supply pipe 10 to remove any residual acidic wastewater inside the pipe. After flushing for a period of time, open the sampling valve 301 to take samples for testing. After all tests are passed, close the first valve 401 and the second valve 501, open the waste acid pump in the waste acid tank, and open the water supply pipe outlet valve 102 for normal discharge.

[0018] Overall benefits: After shutting down 6 12.3kw water pumps, the system operated stably, and the annual maintenance cost dropped from RMB 1.254 million to RMB 100,000 (a reduction of 92%), with no environmental accidents occurring. Example 2

[0019] Treatment capacity: 350 m³ of chromium- and acid-containing wastewater per day; sedimentation tank surface area: 80 m²; foam coverage area: 12 m² (accounting for 1 / 6, less than 1 / 5). Basic parameters: The original flocculant dosage was fixed at 20 kg / h, the filter press was a hot wire filter press, the test tank volume was 0 m³, and the parameters of APU waste acid water met the requirements of Table 5 (nitric acid 35 g / l, hydrofluoric acid 7 g / l, metal ions 48 g / l).

[0020] Its treatment process includes the following steps: (1) Dynamic control of flocculants at the source: Adjust the flocculant dosage by 0.7-0.8 times the original dosage, with an actual dosage of 14 kg / h. Check the foam area every 2 hours through a visual monitoring device to maintain a stable dosage. (2) Filter press overflow blocking: The filter press pressing pressure is set to 1.1MPa, pressing time is 1500s, blowing time is 800s, venting time is 300s, and the processing flow rate is controlled at 115m³ / h; the mixed acid liquid level is 1.6m on the same day (between 1.5-2.0m), and the pressing time is adjusted to 1100s as required; (3) The monitoring tank reflux ratio is 25%, and the reflux flow rate is calculated to be 8.75 m³ / h (350 m³ / d ÷ 24h × 25%). Ensure that the water flow velocity in the tank is 0.35 m / s. Start the APU waste acid water online cleaning circuit every six months and continuously flush the pipeline for 120 minutes to prevent scale buildup. (4) Pass the waste acid water containing nitric acid and hydrofluoric acid in the waste acid tank into the external water supply pipe for reverse flushing. The 150mm scale layer on the inner wall of the 600-meter pipe is completely removed, and the inner diameter of the pipe is restored to 100%.

[0021] After the system has been running continuously and stably for one month, the pressure of the external pipeline was monitored by the pressure sensor and stabilized at 0.4MPa. The flow monitor showed no decrease in flow rate (maintained at 115m³ / h). After confirming that the delivery capacity was sufficient, the six 12.3kw redundant water pumps were shut down.

[0022] Overall benefits: After shutting down 6 12.3kw water pumps, the system operated stably, and the annual maintenance cost dropped from 1.254 million yuan to 120,000 yuan (a reduction of 90.4%), with no environmental accidents occurring. Example 3

[0023] Treatment capacity: 350 m³ of chromium- and acid-containing wastewater per day; sedimentation tank surface area: 80 m²; scum coverage area: 20 m² (accounting for 1 / 4, higher than 1 / 5, and lower than 1 / 3). Basic parameters: The original flocculant dosage was fixed at 20 kg / h, the filter press was a hot wire filter press, the test tank volume was 50 m³, and the parameters of the APU waste acid water met the requirements of Table 5 (nitric acid 35 g / l, hydrofluoric acid 7 g / l, metal ions 48 g / l).

[0024] Its treatment process includes the following steps: (1) Dynamic control of flocculants at the source: Adjust the flocculant dosage by 0.9-1 times the original dosage, with an actual dosage of 18 kg / h. Check the foam area every 2 hours through a visual monitoring device to maintain a stable dosage. (2) Filter press overflow blocking: The filter press pressing pressure is set to 1.1MPa, the total time is 1600s, the pressing time is 800s, the blowing time is 600s, the venting time is 200s, the processing flow rate is controlled at 115m³ / h, and the filter cake moisture content is 38% (≤42%). (3) The monitoring tank reflux ratio is 25%, and the reflux flow rate is calculated to be 8.75 m³ / h (350 m³ / d ÷ 24h × 25%). Ensure that the water flow velocity in the tank is 0.35 m / s. Start the APU waste acid water online cleaning circuit every six months and continuously flush the pipeline for 120 minutes to prevent scale buildup. (4) Pass the waste acid water containing nitric acid and hydrofluoric acid in the waste acid tank into the external water supply pipe for reverse flushing. The 150mm scale layer on the inner wall of the 600-meter pipe is completely removed, and the inner diameter of the pipe is restored to 100%.

[0025] After the system has been running continuously and stably for one month, the pressure of the external pipeline was monitored by the pressure sensor and stabilized at 0.4MPa. The flow monitor showed no decrease in flow rate (maintained at 115m³ / h). After confirming that the delivery capacity was sufficient, the six 12.3kw redundant water pumps were shut down.

[0026] Overall benefits: After shutting down 6 12.3kw water pumps, the system operated stably, and the annual maintenance cost dropped from RMB 1.254 million to RMB 150,000 (a reduction of 88%), with no environmental accidents occurring.

[0027] Comparative Example 1 Comparative Example 1, which only dynamically adjusts the flocculant addition ratio without optimizing subsequent process parameters, exhibits a phenomenon of "short-term effectiveness but prominent long-term hidden dangers": 1. In the short term, the flocculation reaction rate is significantly accelerated, and suspended particles in wastewater can quickly aggregate into large flocs, improving the initial efficiency of static settling or pressure filtration; at the same time, the ability to capture fine colloidal particles is temporarily enhanced, and the turbidity of the effluent can be reduced in the short term. 2. The core hidden danger is that excessively large flocs are prone to stratification, resulting in poor sludge compaction after settling. This not only increases the moisture content of the filter cake but also directly increases the difficulty of subsequent sludge disposal; in addition, the residual components of the flocculant can easily cause scaling in the external drainage pipes and pumps, affecting the long-term operational stability of the equipment.

[0028] Comparative Example 2 Comparative Example 2 only optimized the filter press parameters and used a flow control valve to recirculate 20%-30% of the wastewater from the centrifugal pump outlet of the monitoring tank back to the monitoring tank, controlling the flow velocity in the monitoring tank to ≥0.3m / s to maintain a dynamic spiral shape in the water body. However, it did not dynamically adjust the flocculant or periodically backwash the pipeline pump with waste acid. The following situation occurred during the operation of this scheme: 1) The dosage of flocculant is fixed and cannot be adapted to the fluctuations in water quality (concentration, pH) and water volume. Either the amount of agent is insufficient, resulting in small and loose flocs, or the amount is excessive, causing the flocs to stick together. Neither of these can match the optimized filter press parameters.

[0029] 2) When unsuitable flocs enter the filter press, problems such as excessively rapid filter cloth clogging and uneven filter cake formation will occur. Even if the filter press parameters are optimized, it will be difficult to improve the solid-liquid separation efficiency, and the filter cake will have a high moisture content and be difficult to peel off.

[0030] 3) If the pipeline pump is not regularly acid-washed, calcium and magnesium ions in the water combine with unreacted reagent residues to form hard scale on the inner wall of the pipeline and the flow channel of the pump body. This gradually reduces the flow cross-sectional area, leading to increased pipeline resistance and insufficient pump head. Scale will reduce the operating efficiency of the pump body, and energy consumption will continue to rise. In severe cases, it will cause partial blockage of the pipeline or pump body jamming, directly interrupting the continuous operation of the system. It will also accelerate the corrosion of the pipeline and pump body, shorten the service life of the equipment. At the same time, the scale that falls off may enter the filter press, causing secondary blockage of the filter cloth. This, combined with the problem of "incompatible flocculant", forms a vicious cycle.

[0031] Comparative Example 3 Comparative Example 3 only dynamically adjusted the flocculant and used a flow control valve to recirculate 20%-30% of the wastewater from the centrifugal pump outlet of the monitoring tank back to the monitoring tank, controlling the flow velocity in the monitoring tank to ≥0.3m / s to maintain a dynamic spiral shape in the water body. However, the filter press pressure parameters were not optimized, and the pipeline was not regularly backwashed with waste acid. The following problems occurred during system operation: 1) Filter press pressure not optimized: Solid-liquid separation effect is unbalanced. 1.1) After the flocculant is adjusted, the size and strength of the flocs have changed, and the original pressure cannot match the characteristics of the new flocs.

[0032] 1.2) Insufficient pressure will cause flocs to penetrate the filter cloth, resulting in a rebound in effluent turbidity; excessive pressure will compact the filter cloth pores, causing a sharp increase in filtration resistance. Uneven filter cake formation, with some areas over-compacted and others porous, not only leads to a higher moisture content in the filter cake but also prolongs the filtration cycle and reduces the throughput per unit time. Long-term pressure mismatch will exacerbate filter cloth wear and clogging, increasing the frequency of filter cloth replacement and raising operating costs.

[0033] 2) Pipelines are not backwashed regularly: After dynamically adjusting the flocculant, residual or unreacted components can combine with calcium and magnesium ions in the water to form hard scale on the inner wall of the pipeline. Scale reduces the cross-sectional area of ​​the pipeline, leading to increased pipeline resistance, increased pump energy consumption, and in severe cases, local blockage of the pipeline, interrupting continuous operation. It also corrodes the inner wall of the pipeline, shortens the service life of the pipeline, and increases maintenance downtime.

[0034] When the surface area of ​​the sedimentation tank covered by foam is 1 / 5 or 1 / 3 of the surface area of ​​the sedimentation tank, the overall benefits of this invention are comparable to those of Example 3, provided that the other experimental parameters are basically the same as those of Example 3 and only the surface area of ​​the sedimentation tank covered by foam is different.

[0035] As can be seen from Examples 1-3 and Comparative Examples 1-3, only by implementing a comprehensive scale control process encompassing "source control - process optimization - end-of-pipe protection" can the scale control effect be more lasting and thorough. After process improvement, by optimizing flocculant dosage, increasing filter press efficiency, modifying the reflux system, and disabling redundant water pumps, annual maintenance costs can be reduced by over 1 million yuan, while also reducing manual maintenance workload. Furthermore, the equipment used in the solution (filter press, PPH pipeline, reflux valve) are all conventional industrial equipment, making modification difficult and implementation time short, and it can be widely applied to other wastewater treatment companies with similar scaling problems.

[0036] The above description is merely an embodiment of the present invention and does not limit the patent scope of the present invention. Any equivalent process transformations made using the content of the present invention specification, or direct or indirect applications in other related technical fields, are similarly included within the patent protection scope of the present invention.

Claims

1. A process for treating scaling on the external water supply pipe and pump body of a public auxiliary chromium-containing wastewater treatment system, wherein the public auxiliary chromium-containing wastewater treatment system comprises a waste acid tank, a distribution tank, a waste acid neutralization tank, a sedimentation tank, a filter press, and a monitoring tank connected in sequence by pipes, wherein the monitoring tank is connected to an external water supply pipe, and the external water supply pipe is equipped with an external water supply inlet valve and an external water supply outlet valve; characterized in that: Its treatment process includes the following steps: (1) Dynamic control of flocculants at the source: In the flocculation and clarification stage, when the surface area of ​​the sedimentation tank covered by foam is greater than 1 / 3 of the surface area of ​​the sedimentation tank, the amount of flocculant added is increased to 1.3-1.4 times the fixed amount of conventional flocculant added; when the surface area of ​​the sedimentation tank covered by foam is greater than or equal to 1 / 5 of the surface area of ​​the sedimentation tank and less than or equal to 1 / 3 of the surface area of ​​the sedimentation tank, the amount of flocculant added is increased to 0.9-1 times the fixed amount of conventional flocculant added; when the surface area of ​​the sedimentation tank covered by foam is less than 1 / 5 of the surface area of ​​the sedimentation tank, the amount of flocculant added is reduced to 0.7-0.8 times the fixed amount of conventional flocculant added. (2) Filter press overflow prevention: The filter press processing flow rate, pressing pressure and pressing time are comprehensively controlled. The filter press processing flow rate is controlled at ≥110m³ / h, the pressing pressure is controlled at ≥1.1Mpa, and the pressing time is controlled at 800-1300s. The upper limit of the filter press processing flow rate and the upper limit of the pressing pressure are limited to the state where the wastewater in the sedimentation tank does not need to overflow. (3) A return pipe is added between the monitoring tank and the external water supply pipe. A return pipe valve is installed on the return pipe. 20%-30% of the wastewater from the centrifugal pump outlet of the monitoring tank is returned to the monitoring tank through the return pipe valve. The flow velocity of the monitoring tank is controlled to be ≥0.3m / s so that the water in the tank remains in a dynamic spiral shape and crystallization is avoided due to water stagnation. (4) The waste acid water containing nitric acid and hydrofluoric acid in the waste acid tank is passed into the external water supply pipe for reverse flushing. The flushed waste water is returned to the distribution tank for treatment.

2. The scaling treatment process for the external water supply pipe and pump body of the auxiliary chromium-containing wastewater treatment system according to claim 1, characterized in that: A sampling pipeline connected to the external water supply pipe is installed between the inlet valve and the outlet valve of the external water supply pipe. The sampling pipeline is adjacent to the outlet valve of the external water supply pipe. A first waste acid pipe connected to the waste acid tank is installed on the external water supply pipe between the inlet valve and the sampling pipeline. The first waste acid pipe is located close to the sampling pipeline. A second waste acid pipe connected to the distribution tank is installed between the inlet valve and the first waste acid pipe. A first valve is installed on the first waste acid pipe, and a second valve is installed on the second waste acid pipe. A sampling valve is installed on the sampling pipeline.

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