Pretreatment process for improving compatibility of river and lake sludge in saline-alkali soil

Abstract

The present application relates to the technical field of sludge treatment, and particularly relates to a pretreatment process for improving compatibility of river and lake sludge in saline-alkali soil, which performs pretreatment process on river and lake sludge through salt washing and alkali reduction, structure solidification and nutrient activation, and finally obtains river and lake sludge with good compatibility with saline-alkali soil; in the salt washing and alkali reduction, physical desalination effect is achieved through washing, and further chemical alkali breaking is achieved by using citric acid and acidity regulator; in the structure solidification, the sludge is deodorized, water retention and air permeability are improved by using sludge modifier, so that the sludge has relatively stable internal structure; in the nutrient activation process, various salt-tolerant and alkali-tolerant microorganisms are used to further decompose organic matter in the sludge, improve the fertility of the sludge, and eliminate harmful bacteria in the sludge, so that the pretreated sludge is rich in various beneficial microorganisms and nutrients, and the compatibility with saline-alkali soil is further improved, which has wide application prospect.

Description

Technical Field

[0001] This invention relates to the field of sludge treatment technology, and in particular to a pretreatment process for improving the compatibility of river and lake sludge with saline-alkali soil. Background Technology

[0002] Saline-alkali soil is a general term for saline soil, alkaline soil, and various types of salinized and alkalized soils. Saline soil refers to soil containing a large amount of soluble salts, making it impossible for most plants to grow; its salt content is generally above 0.6%. Alkaline soil refers to strongly alkaline soil with an exchangeable sodium ion cation exchange rate (ESP) exceeding 20%. Saline soil has poor physical and chemical properties, mainly characterized by excessively high salt or alkalinity, leading to water shortage or poisoning of plant roots. It also has a heavy, sticky texture with few aggregates, and becomes compacted during drought, resulting in poor water and aeration, which is extremely detrimental to agricultural production.

[0003] Currently, measures for managing saline-alkali land can be broadly categorized into engineering improvement, chemical improvement, and biological improvement. Among these, engineering improvement measures mainly involve land leveling, digging drainage ditches, tilling, rotary tillage, and paddy field soaking. These measures utilize open or vertical drainage to lower the water level and reduce the rise of salinity, or improve the land by rinsing off the salinity through irrigation, or constructing salt drainage pipes and drainage holes to remove the salt from the saline-alkali land.

[0004] Silt is mainly found in waterways, particularly in slow-flowing or even stagnant rivers. It forms through biochemical processes and its formation impacts navigation, water quality, and the river environment. Dredged silt contains significant amounts of organic matter, including elements essential for plant growth such as nitrogen, phosphorus, and potassium. After resource recovery treatment, silt must meet specific requirements: heavy metals and toxic organic compounds must not exceed limits, and odors must be eliminated while nutrients are retained. Using treated silt as fertilizer can improve soil structure and prevent soil compaction.

[0005] Currently, dredged silt has been used as a soil conditioner to improve saline-alkali land. However, there are problems with the mixing of dredged silt and saline-alkali soil, such as pH conflict, salt conflict, and nutrient deficiency.

[0006] Therefore, based on the relevant technologies mentioned above, there is an urgent need to develop a pretreatment process to improve the compatibility of river and lake silt with saline-alkali soil. Summary of the Invention

[0007] In view of this, the purpose of this invention is to propose a pretreatment process to improve the compatibility of river and lake silt with saline-alkali soil, so as to solve the problem of poor compatibility between saline-alkali soil and river and lake silt in the prior art.

[0008] To achieve the above objectives, the present invention provides a pretreatment process for improving the compatibility of river and lake silt with saline-alkali soil.

[0009] A pretreatment process for improving the compatibility of river and lake silt with saline-alkali soil includes the following steps:

[0010] Step S1. Dewater and crush the dredged sludge. After dewatering, the water content of the sludge should be ≤55%. Wash it once with a citric acid solution with a mass fraction of 0.1%-0.2%, then wash it 2-3 times with deionized water, drain it, and add an acidity regulator to adjust the pH of the system to 7-7.2 to obtain pretreated sludge A.

[0011] Step S2. Add sludge conditioner to pretreated sludge A, mix thoroughly and evenly, and then pile and age for 5-7 days to obtain pretreated sludge B;

[0012] Step S3. Inoculate the pretreated sludge B with a microbial compound inoculant, turn the pile evenly, ferment, and after fermentation, let it cool naturally to 25-30℃ and let it stand for aging for 15-20 days to obtain river and lake sludge with good compatibility with saline-alkali soil.

[0013] The sludge conditioner mentioned in step S2 is obtained by mixing sludge conditioner A and sludge conditioner B in a mass ratio of 9-13.6:4.3-7.5.

[0014] Preferably, the acidity regulator in step S1 includes acidity regulator A and acidity regulator B;

[0015] The acidity regulator A is prepared from straw, distiller's grains and sawdust;

[0016] The acidity regulator B is phosphogypsum.

[0017] Preferably, the acidity regulator A is prepared by the following method:

[0018] Step A1. Dry the straw, distiller's grains and sawdust to a moisture content of ≤12%, crush them to 1-3 mm using a pulverizer, mix them with 0.2-0.3 mol / L sodium hydroxide solution and add them to a reaction vessel. Heat, stir and centrifuge to obtain the extract.

[0019] Step A2. While stirring, add citric acid to the extract to adjust the pH of the system to 6-6.5. After standing for 12-15 hours, take the supernatant A and solid waste B. The supernatant A is the acidity regulator A.

[0020] Preferably, the ratio of straw, distiller's grains, sawdust and sodium hydroxide solution used in step A1 is 2-5g:2-5g:2-5g:60-160mL;

[0021] The heating and stirring process is carried out at a temperature of 70-75℃ for 5-6 hours.

[0022] Preferably, the sludge conditioner A is obtained by mixing solid waste B, coconut coir, sodium alginate and xanthan gum in a mass ratio of 3-6:3-6:5.5-8:4-6.

[0023] Preferably, the sludge conditioner B is obtained by mixing red brick powder, bentonite, and Bacillus cereus in a mass ratio of 13.9-17:3.5-7:2-5;

[0024] The total iron content (calculated as ferric oxide content) of the red brick powder is ≥3%, and the particle size is 100-150 mesh.

[0025] Preferably, the microbial compound inoculant in step S3 is prepared from Bacillus subtilis, Bacillus thuringiensis, and Klebsiella pneumoniae.

[0026] Preferably, the Bacillus proteolyticus, Bacillus subtilis and Klebsiella pneumoniae are arranged in the form of Bacillus proteolyticus suspension, Bacillus subtilis suspension and Klebsiella pneumoniae suspension to form a microbial compound agent;

[0027] The mass ratio of the Bacillus subtilis suspension, Bacillus thuringiensis suspension, and Klebsiella pneumoniae suspension is 3-7:2-5:2-5.

[0028] The viable count of *Bacillus proteolyticus* in the microbial compound inoculant is 4 × 10⁻⁶. 7 -4×10 9 CFU / mL, viable count of Bacillus subtilis was 2×10⁻⁶. 8 -2×10 10 CFU / mL, viable Klebsiella pneumoniae count was 5 × 10⁻⁶. 6 -5×10 7 CFU / mL.

[0029] Preferably, in step S3, the fermentation temperature is 50-55℃, the fermentation time is 9-12 days, and the pile is turned over 3-4 times during the fermentation period.

[0030] Preferably, the mass ratio of the pretreated sludge A to the sludge conditioner in step S2 is 100-180:35-55;

[0031] The mass ratio of pretreated sludge B to microbial compound inoculant in step S3 is 75-100:18-30.

[0032] The beneficial effects of this invention are:

[0033] This invention provides a pretreatment process to improve the compatibility of river and lake silt with saline-alkali soil. The process involves salt washing and dealkali reduction, structural solidification, and nutrient activation to pretreat the silt, ultimately yielding silt with good compatibility with saline-alkali soil. In the salt washing and dealkali reduction process, physical desalination is achieved through washing, followed by further chemical dealkali reduction using citric acid and an acidity regulator. The acidity regulator utilizes various agricultural wastes, achieving "waste-to-waste" treatment and resource recycling. In the structural solidification process, a silt amendment deodorizes the silt, improves water retention and permeability, resulting in a more stable internal structure. During the nutrient activation process, various salt- and alkali-tolerant microorganisms further decompose the organic matter in the silt, improving its fertility and eliminating harmful bacteria. This results in pretreated silt rich in beneficial microorganisms and sufficient nutrients, further enhancing its compatibility with saline-alkali soil. Compared with existing technologies, this process has broad application prospects. Detailed Implementation

[0034] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to specific embodiments.

[0035] The sources and properties of some of the raw materials used in this invention are as follows:

[0036] The Bacillus subtilis used in this invention is Bacillus subtilis, which is disclosed in the invention patent with authorization announcement number "CN117431195B" entitled "A salt-alkali resistant growth-promoting bacterium, growth-promoting bacterium agent and its application", and accession number CGMCCNO.29057.

[0037] The Bacillus pyriformis used in this invention is Bacillus pyriformis XZT198, which is disclosed in the invention patent with authorization announcement number "CN118440863B" and title "A salt-tolerant bacterial agent and its preparation method and application", and accession number CCTCCM20232321;

[0038] The Klebsiella pneumoniae used in this invention is disclosed in the invention patent with authorization announcement number "CN120866167A" entitled "A salt-alkali resistant compound microbial agent and its application", and accession number CGMCC1.839.

[0039] Example 1: A pretreatment process for improving the compatibility of river and lake silt with saline-alkali soil, comprising the following steps:

[0040] S1. Weigh 10g of tryptone, 5g of yeast powder, and 10g of NaCl, add 1000mL of distilled water, heat at 40℃ until completely dissolved, adjust the pH to 7, filter, and sterilize at 121℃ for 15min to obtain LB liquid culture medium.

[0041] S2. Activated Bacillus subtilis, Bacillus proteolyticus XZT198, and Klebsiella pneumoniae were inoculated into LB liquid medium and cultured in a shaker at 28°C and 140 rpm for 3 days. After centrifuging the fermentation broth at 8000 rpm for 10 min, the bacterial cells were collected and prepared into bacterial suspensions with sterile water to obtain Bacillus proteolyticus, Bacillus subtilis, and Klebsiella pneumoniae bacterial suspensions, respectively. Then, 3g of Bacillus proteolyticus, 2g of Bacillus subtilis, and 2g of Klebsiella pneumoniae bacterial suspensions were mixed to obtain a microbial compound inoculant.

[0042] S3. Dry 2g of straw, 2g of distiller's grains and 2g of sawdust to a moisture content of ≤12%, crush them to 1mm using a pulverizer, mix them with 60mL of 0.2mol / L sodium hydroxide solution and add them to a reaction vessel. Heat and stir at 70℃ for 5h, then centrifuge to obtain the extract.

[0043] S4. While stirring, add citric acid to the extract to adjust the pH of the system to 6, then let it stand for 12 hours. Take the supernatant A and solid waste B. The supernatant A is the acidity regulator A.

[0044] S5. Dehydrate and crush the dredged sludge. After dehydration, the sludge has a water content of ≤55%. Wash it once with a 0.1% citric acid solution, then wash it twice with deionized water, drain it, add acidity regulator A, mix it evenly, and then add phosphogypsum to adjust the pH of the system to 7 to obtain pretreated sludge A.

[0045] S6. Mix 3g of solid waste B, 3g of coconut coir, 5.5g of sodium alginate and 4g of xanthan gum to obtain sludge conditioner A. Then mix 13.9g of red brick powder, 3.5g of bentonite and 2g of Bacillus cereus evenly to obtain sludge conditioner B. Mix 9g of sludge conditioner A and 4.3g of sludge conditioner B completely to obtain sludge conditioner. Add 35g of sludge conditioner to 100g of pretreated sludge A, mix thoroughly, and let it stand for 5 days to obtain pretreated sludge B.

[0046] S7. Inoculate 18g of microbial compound agent into 75g of pretreated sludge B, turn the pile evenly, ferment, and after fermentation, let it cool naturally to 25℃ and let it stand for aging for 15 days to obtain river and lake sludge with good compatibility with saline-alkali soil.

[0047] Example 2: A pretreatment process for improving the compatibility of river and lake silt in saline-alkali soil, comprising the following steps:

[0048] S1. Weigh 10g of tryptone, 5g of yeast powder, and 10g of NaCl, add 1000mL of distilled water, heat at 40℃ until completely dissolved, adjust the pH to 7, filter, and sterilize at 121℃ for 15min to obtain LB liquid culture medium.

[0049] S2. Activated Bacillus subtilis, Bacillus xZT198, and Klebsiella pneumoniae were inoculated into LB liquid medium and cultured in a shaker at 28°C and 140 rpm for 3 days. After centrifuging the fermentation broth at 8000 rpm for 10 min, the bacterial cells were collected and prepared into bacterial suspensions with sterile water to obtain Bacillus xZT198, Bacillus subtilis, and Klebsiella pneumoniae bacterial suspensions, respectively. Then, 3.5 g of Bacillus xZT198, 2.5 g of Bacillus subtilis, and 2.5 g of Klebsiella pneumoniae bacterial suspensions were mixed to obtain a microbial compound inoculant.

[0050] S3. Dry 2.5g of straw, 2.5g of distiller's grains and 2.5g of sawdust to a moisture content of ≤12%, crush them to 1mm using a pulverizer, mix them with 80mL of 0.23mol / L sodium hydroxide solution and add them to a reaction vessel. Heat and stir at 70℃ for 5h, then centrifuge to obtain the extract.

[0051] S4. While stirring, add citric acid to the extract to adjust the pH of the system to 6, and then let it stand for 13 hours. Take the supernatant A and solid waste B. The supernatant A is the acidity regulator A.

[0052] S5. Dehydrate and crush the dredged sludge. After dehydration, the sludge has a water content of ≤55%. Wash it once with a 0.1% citric acid solution, then wash it twice with deionized water, drain it, add acidity regulator A, mix it evenly, and then add phosphogypsum to adjust the pH of the system to 7 to obtain pretreated sludge A.

[0053] S6. Mix 3.5g solid waste B, 3.5g coconut coir, 6g sodium alginate and 4.5g xanthan gum to obtain sludge conditioner A. Then mix 14.5g red brick powder, 4g bentonite and 2.5g Bacillus cereus evenly to obtain sludge conditioner B. Mix 10.5g sludge conditioner A and 4.8g sludge conditioner B completely to obtain sludge conditioner. Add 40g sludge conditioner to 120g pretreated sludge A, mix thoroughly, and let it stand for 5 days to obtain pretreated sludge B.

[0054] S7. Inoculate 20g of microbial compound agent into 83g of pretreated sludge B, turn the pile evenly, ferment, and after fermentation, let it cool naturally to 25℃ and let it stand for 15 days to obtain river and lake sludge with good compatibility with saline-alkali soil.

[0055] Example 3: A pretreatment process for improving the compatibility of river and lake silt in saline-alkali soil, comprising the following steps:

[0056] S1. Weigh 10g of tryptone, 5g of yeast powder, and 10g of NaCl, add 1000mL of distilled water, heat at 40℃ until completely dissolved, adjust the pH to 7, filter, and sterilize at 121℃ for 15min to obtain LB liquid culture medium.

[0057] S2. Activated Bacillus subtilis, Bacillus proteolyticus XZT198, and Klebsiella pneumoniae were inoculated into LB liquid medium and cultured in a shaker at 28°C and 140 rpm for 3 days. After centrifuging the fermentation broth at 8000 rpm for 10 min, the bacterial cells were collected and prepared into bacterial suspensions with sterile water to obtain Bacillus proteolyticus, Bacillus subtilis, and Klebsiella pneumoniae bacterial suspensions, respectively. Then, 4 g of Bacillus proteolyticus, 3 g of Bacillus subtilis, and 3 g of Klebsiella pneumoniae bacterial suspensions were mixed to obtain a microbial compound inoculant.

[0058] S3. Dry 3g of straw, 3g of distiller's grains and 3g of sawdust to a moisture content of ≤12%, crush them to 2mm using a pulverizer, mix them with 100mL of 0.25mol / L sodium hydroxide solution and add them to a reaction vessel. Heat and stir at 72℃ for 5.5h, then centrifuge to obtain the extract.

[0059] S4. While stirring, add citric acid to the extract to adjust the pH of the system to 6, and then let it stand for 14 hours. Take the supernatant A and solid waste B. The supernatant A is the acidity regulator A.

[0060] S5. Dehydrate and crush the dredged sludge. After dehydration, the moisture content of the sludge is ≤55%. Wash it once with a 0.2% citric acid solution, then wash it three times with deionized water, drain it, add acidity regulator A, mix it evenly, and then add phosphogypsum to adjust the pH of the system to 7.1 to obtain pretreated sludge A.

[0061] S6. Mix 4g of solid waste B, 4g of coconut coir, 6.5g of sodium alginate and 5g of xanthan gum to obtain sludge conditioner A. Then mix 15.5g of red brick powder, 4.5g of bentonite and 3g of Bacillus cereus evenly to obtain sludge conditioner B. Mix 12g of sludge conditioner A and 5.5g of sludge conditioner B completely to obtain sludge conditioner. Add 45g of sludge conditioner to 140g of pretreated sludge A, mix thoroughly, and then let it stand for 6 days to obtain pretreated sludge B.

[0062] S7. Inoculate 25g of microbial compound agent into 90g of pretreated sludge B, turn the pile evenly, ferment, and after fermentation, let it cool naturally to 28℃ and let it stand for aging for 17 days to obtain river and lake sludge with good compatibility with saline-alkali soil.

[0063] Example 4: A pretreatment process for improving the compatibility of river and lake silt with saline-alkali soil, comprising the following steps:

[0064] S1. Weigh 10g of tryptone, 5g of yeast powder, and 10g of NaCl, add 1000mL of distilled water, heat at 40℃ until completely dissolved, adjust the pH to 7, filter, and sterilize at 121℃ for 15min to obtain LB liquid culture medium.

[0065] S2. Activated Bacillus subtilis, Bacillus proteolyticus XZT198, and Klebsiella pneumoniae were inoculated into LB liquid medium and cultured on a shaker at 28°C and 140 rpm for 3 days. After centrifuging the fermentation broth at 8000 rpm for 10 min, the bacterial cells were collected and prepared into bacterial suspensions with sterile water to obtain Bacillus proteolyticus, Bacillus subtilis, and Klebsiella pneumoniae bacterial suspensions, respectively. Then, 5 g of Bacillus proteolyticus, 4 g of Bacillus subtilis, and 4 g of Klebsiella pneumoniae bacterial suspensions were mixed to obtain a microbial compound inoculant.

[0066] S3. Dry 4g of straw, 4g of distiller's grains and 4g of sawdust to a moisture content of ≤12%, crush them to 2mm using a pulverizer, mix them with 120mL of 0.27mol / L sodium hydroxide solution and add them to a reaction vessel. Heat and stir at 73℃ for 5h, then centrifuge to obtain the extract.

[0067] S4. While stirring, add citric acid to the extract to adjust the pH of the system to 6, and then let it stand for 14 hours. Take the supernatant A and solid waste B. The supernatant A is the acidity regulator A.

[0068] S5. Dehydrate and crush the dredged sludge. After dehydration, the sludge has a water content of ≤55%. Wash it once with a 0.2% citric acid solution, then wash it three times with deionized water, drain it, add acidity regulator A, mix it evenly, and then add phosphogypsum to adjust the pH of the system to 7.2 to obtain pretreated sludge A.

[0069] S6. Mix 5g solid waste B, 5g coconut coir, 7g sodium alginate and 5.5g xanthan gum to obtain sludge conditioner A. Then mix 16.3g red brick powder, 6g bentonite and 4g Bacillus cereus evenly to obtain sludge conditioner B. Mix 12.8g sludge conditioner A and 6.3g sludge conditioner B completely to obtain sludge conditioner. Add 50g sludge conditioner to 160g pretreated sludge A, mix thoroughly, and then pile and age for 6 days to obtain pretreated sludge B.

[0070] S7. Inoculate 28g of microbial compound agent into 95g of pretreated sludge B, turn the pile evenly, ferment, and after fermentation, let it cool naturally to 30℃ and let it stand for 20 days to obtain river and lake sludge with good compatibility with saline-alkali soil.

[0071] Example 5: A pretreatment process for improving the compatibility of river and lake silt with saline-alkali soil, comprising the following steps:

[0072] S1. Weigh 10g of tryptone, 5g of yeast powder, and 10g of NaCl, add 1000mL of distilled water, heat at 40℃ until completely dissolved, adjust the pH to 7, filter, and sterilize at 121℃ for 15min to obtain LB liquid culture medium.

[0073] S2. Activated Bacillus subtilis, Bacillus xZT198, and Klebsiella pneumoniae were inoculated into LB liquid medium and cultured in a shaker at 28°C and 140 rpm for 3 days. After centrifuging the fermentation broth at 8000 rpm for 10 min, the bacterial cells were collected and prepared into bacterial suspensions with sterile water to obtain Bacillus xZT198, Bacillus subtilis, and Klebsiella pneumoniae bacterial suspensions, respectively. Then, 7 g of Bacillus xZT198, 5 g of Bacillus subtilis, and 5 g of Klebsiella pneumoniae bacterial suspensions were mixed to obtain a microbial compound inoculant.

[0074] S3. Dry 5g of straw, 5g of distiller's grains and 5g of sawdust to a moisture content of ≤12%, crush them to 3mm using a pulverizer, mix them with 160mL of 0.3mol / L sodium hydroxide solution and add them to a reaction vessel. Heat and stir at 75℃ for 6h, then centrifuge to obtain the extract.

[0075] S4. While stirring, add citric acid to the extract to adjust the pH of the system to 6.5. After standing for 15 hours, take the supernatant A and solid waste B. The supernatant A is the acidity regulator A.

[0076] S5. Dehydrate and crush the dredged sludge. After dehydration, the sludge has a water content of ≤55%. Wash it once with a 0.2% citric acid solution, then wash it three times with deionized water, drain it, add acidity regulator A, mix it evenly, and then add phosphogypsum to adjust the pH of the system to 7.2 to obtain pretreated sludge A.

[0077] S6. Mix 6g of solid waste B, 6g of coconut coir, 8g of sodium alginate and 6g of xanthan gum to obtain sludge conditioner A. Then mix 17g of red brick powder, 7g of bentonite and 5g of Bacillus cereus evenly to obtain sludge conditioner B. Mix 13.6g of sludge conditioner A and 7.5g of sludge conditioner B completely to obtain sludge conditioner. Add 55g of sludge conditioner to 180g of pretreated sludge A, mix thoroughly, and then pile and age for 7 days to obtain pretreated sludge B.

[0078] S7. Inoculate 30g of microbial compound agent into 100g of pretreated sludge B, turn the pile evenly, ferment, and after fermentation, let it cool naturally to 30℃ and let it stand for 20 days to obtain river and lake sludge with good compatibility with saline-alkali soil.

[0079] Comparative Example 1:

[0080] Compared with Example 1, no silt conditioner was added in step S2 in this comparative example. All other steps and parameters are the same, and will not be repeated here. The final result is river and lake silt with good compatibility with saline-alkali soil.

[0081] Comparative Example 2:

[0082] Compared with Example 1, this comparative example did not add microbial compound inoculant in step S3. All other steps and parameters were the same, and will not be repeated here. The final result was river and lake silt with good compatibility with saline-alkali soil.

[0083] Comparative Example 3:

[0084] Compared with Example 1, this comparative example did not add an acidity regulator in step S1. All other steps and parameters were the same, and will not be repeated here. The final result was river and lake silt with good compatibility with saline-alkali soil.

[0085] Comparative Example 4:

[0086] Compared with Example 1, this comparative example only replaces "acidity regulator" with "acidity regulator A". All other steps and parameters are the same, and will not be repeated here. The final result is river and lake silt with good compatibility with saline-alkali soil.

[0087] Comparative Example 5:

[0088] Compared with Example 1, this comparative example only replaces "acidity regulator" with "acidity regulator B". All other steps and parameters are the same, and will not be repeated here. The final result is river and lake silt with good compatibility with saline-alkali soil.

[0089] Comparative Example 6:

[0090] Compared with Example 1, this comparative example only replaces "sludge conditioner" with "sludge conditioner B". All other steps and parameters are the same, and will not be repeated here. The final result is river and lake sludge with good compatibility with saline-alkali soil.

[0091] Comparative Example 7:

[0092] Compared with Example 1, this comparative example only replaces "sludge conditioner" with "sludge conditioner A". All other steps and parameters are the same, and will not be repeated here. The final result is river and lake sludge with good compatibility with saline-alkali soil.

[0093] Performance testing:

[0094] A piece with a density of 1.7 g / cm³ 3 The saline-alkali land in the port area with a pH value of 8.5 and a salt content of 0.65% was divided into 12 groups. The pretreated sludge prepared in Examples 1-5 and Comparative Examples 1-7 was spread on the 12 groups of saline-alkali land respectively, with an application rate of 900 kg / mu. After the application, the land was deep-plowed to incorporate the pretreated sludge into the soil. The saline-alkali land was plowed multiple times to ensure that the saline-alkali soil and the pretreated sludge were mixed evenly. Ten days after application, the density, pH value and salt content of each group of saline-alkali land were measured.

[0095] Table 1 Summary of experimental data from Examples 1-5 and Comparative Examples 1-7

[0096] project <![CDATA[Density g / cm 3 > pH value Salt content / % Example 1 1.22 7.4 0.21 Example 2 1.28 7.3 0.18 Example 3 1.37 7.2 0.25 Example 4 1.20 7.5 0.28 Example 5 1.29 7.2 0.30 Comparative Example 1 1.47 7.8 0.46 Comparative Example 2 1.39 7.7 0.41 Comparative Example 3 1.56 8.1 0.52 Comparative Example 4 1.29 7.5 0.36 Comparative Example 5 1.30 7.4 0.32 Comparative Example 6 1.39 7.8 0.38 Comparative Example 7 1.37 7.7 0.42

[0097] Data Analysis:

[0098] As shown in Table 1, the pretreated sludge prepared by this invention exhibits better compatibility with saline-alkali land. This is likely due to the pretreatment process of the river and lake sludge, which involves salt washing and alkali reduction, structural solidification, and nutrient activation, ultimately resulting in river and lake sludge with good compatibility with saline-alkali soil. In the salt washing and alkali reduction process, physical desalination is achieved through washing, followed by further chemical alkali reduction using citric acid and an acidity regulator. The acidity regulator utilizes various agricultural wastes, achieving "waste treatment of waste" and resource recycling. In the structural solidification process, a sludge amendment is used to deodorize, improve water retention and air permeability, resulting in a more stable internal structure. During the nutrient activation process, various salt- and alkali-tolerant microorganisms are used to further decompose the organic matter in the sludge, improving its fertility and enhancing its overall health. The harmful bacteria in the silt enrich the pretreated sludge with various beneficial microorganisms and sufficient nutrients, further enhancing its compatibility with saline-alkali land. Acidity regulators A and B chemically break down the alkali in the sludge. Acidity regulator B replaces sodium ions in the saline-alkali soil with calcium ions, improving soil structure. It also forms a gel network with sodium alginate in sludge conditioner A, fixing the microbial compound agent and improving its utilization rate. In the sludge conditioner, sludge conditioner A constructs a framework structure through porous materials, possessing both water retention and air permeability, improving soil compaction. Combined with the deodorizing effect of sludge conditioner B, they work synergistically in sludge treatment, enhancing compatibility with saline-alkali land and improving the soil's water retention, anti-compactment, salinity and alkali reduction, and fertility enhancement.

[0099] Those skilled in the art should understand that the discussion of any of the above embodiments is merely exemplary and is not intended to imply that the scope of the invention is limited to these examples; within the framework of the invention, the technical features of the above embodiments or different embodiments can also be combined, the steps can be implemented in any order, and there are many other variations of the different aspects of the invention as described above, which are not provided in detail for the sake of brevity.

[0100] This invention is intended to cover all such substitutions, modifications, and variations that fall within the broad scope of the appended claims. Therefore, any omissions, modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this invention should be included within the scope of protection of this invention.

Claims

1. A pretreatment process for improving the compatibility of river and lake silt with saline-alkali soil, characterized in that, Includes the following steps: Step S1. Dewater and crush the dredged sludge. After dewatering, the water content of the sludge should be ≤55%. Wash it once with a citric acid solution with a mass fraction of 0.1%-0.2%, then wash it 2-3 times with deionized water, drain it, and add an acidity regulator to adjust the pH of the system to 7-7.2 to obtain pretreated sludge A. Step S2. Add sludge conditioner to pretreated sludge A, mix thoroughly and evenly, and then pile and age for 5-7 days to obtain pretreated sludge B; Step S3. Inoculate the pretreated sludge B with a microbial compound inoculant, turn the pile evenly, ferment, and after fermentation, let it cool naturally to 25-30℃ and let it stand for aging for 15-20 days to obtain river and lake sludge with good compatibility with saline-alkali soil. The sludge conditioner mentioned in step S2 is obtained by mixing sludge conditioner A and sludge conditioner B in a mass ratio of 9-13.6:4.3-7.5; The acidity regulator mentioned in step S1 includes acidity regulator A and acidity regulator B; The acidity regulator A is prepared from straw, distiller's grains and sawdust; The acidity regulator B is phosphogypsum; The preparation method of the acidity regulator A is as follows: Step A1. After drying and crushing the straw, distiller's grains and sawdust, mix them with sodium hydroxide solution and add them to the reaction vessel. Heat, stir, and centrifuge to obtain the extract. Step A2. While stirring, add citric acid to the extract to adjust the pH of the system and let it stand to obtain supernatant A and solid waste B. Supernatant A is acidity regulator A. The sludge conditioner A is obtained by mixing solid waste B, coconut coir, sodium alginate and xanthan gum; The sludge conditioner B is obtained by mixing red brick powder, bentonite and Bacillus cereus.

2. The pretreatment process for improving the compatibility of river and lake silt with saline-alkali soil according to claim 1, characterized in that, The preparation method of the acidity regulator A is as follows: Step A1. Dry the straw, distiller's grains and sawdust to a moisture content of ≤12%, crush them to 1-3 mm using a pulverizer, mix them with 0.2-0.3 mol / L sodium hydroxide solution and add them to a reaction vessel. Heat, stir and centrifuge to obtain the extract. Step A2. While stirring, add citric acid to the extract to adjust the pH of the system to 6-6.

5. After standing for 12-15 hours, take the supernatant A and solid waste B. The supernatant A is the acidity regulator A.

3. The pretreatment process for improving the compatibility of river and lake silt with saline-alkali soil according to claim 1, characterized in that, The ratio of straw, distiller's grains, sawdust, and sodium hydroxide solution used in step A1 is 2-5g:2-5g:2-5g:60-160mL; The heating and stirring process is carried out at a temperature of 70-75℃ for 5-6 hours.

4. The pretreatment process for improving the compatibility of river and lake silt with saline-alkali soil according to claim 1, characterized in that, The mass ratio of the solid waste B, coconut coir, sodium alginate, and xanthan gum is 3-6:3-6:5.5-8:4-6.

5. The pretreatment process for improving the compatibility of river and lake silt in saline-alkali soil according to claim 1, characterized in that, The mass ratio of the red brick powder, bentonite, and Bacillus cereus is 13.9-17:3.5-7:2-5; The total iron content of the red brick powder is ≥3%, and the particle size is 100-150 mesh.

6. The pretreatment process for improving the compatibility of river and lake silt with saline-alkali soil according to claim 1, characterized in that, The microbial compound inoculant in step S3 is prepared from Bacillus subtilis, Bacillus thuringiensis, and Klebsiella pneumoniae.

7. The pretreatment process for improving the compatibility of river and lake silt with saline-alkali soil according to claim 6, characterized in that, The Bacillus subtilis, Bacillus thuringiensis, and Klebsiella pneumoniae are combined in the form of Bacillus subtilis suspension, Bacillus thuringiensis suspension, and Klebsiella pneumoniae suspension to form a microbial compound inoculum. The mass ratio of the Bacillus subtilis suspension, Bacillus thuringiensis suspension, and Klebsiella pneumoniae suspension is 3-7:2-5:2-5. The viable count of *Bacillus proteolyticus* in the microbial compound inoculant is 4 × 10⁻⁶. 7 -4×10 9 CFU / mL, viable count of Bacillus subtilis was 2×10⁻⁶. 8 -2×10 10 CFU / mL, viable Klebsiella pneumoniae count was 5 × 10⁻⁶. 6 -5×10 7 CFU / mL.

8. The pretreatment process for improving the compatibility of river and lake silt in saline-alkali soil according to claim 1, characterized in that, In step S3, the fermentation temperature is 50-55℃ and the fermentation time is 9-12 days. The pile is turned over 3-4 times during the fermentation period.

9. The pretreatment process for improving the compatibility of river and lake silt with saline-alkali soil according to claim 1, characterized in that, The mass ratio of pretreated sludge A to sludge conditioner in step S2 is 100-180:35-55; The mass ratio of pretreated sludge B to microbial compound inoculant in step S3 is 75-100:18-30.