DOSAGE OPTIMIZATION METHOD OF CHEMICAL CONDITIONER FOR DEEP DEWATERING OF SLUDGE

Abstract

The present invention discloses a dosage optimization method of a chemical conditioner for deeply dewatering the sludge in a municipal wastewater treatment plant, comprises the following steps: (1) optimizing a dosage of a chemical conditioner added into a specific sludge to obtain an optimal dosage proportion of the chemical conditioner corresponding to unit mass of organic matter; (2) calculating an optimal dosage of the chemical conditioner applicable for other sludge to be treated; and (3) adding the chemical conditioner into the sludge to be treated for sludge conditioning treatment, and then performing mechanical dewatering treatment, so as to obtain a deeply dewatered sludge with a moisture content of less than 60%. By improving the reference basis as the key chemical conditioner dosage, the method can effectively solve the problem that types and moisture content range of sludge to which the chemical conditioner dosage control method is applicable are narrow.

Claims

1. A dosage optimization method of a chemical conditioner for dewatering sludge, comprising following steps of: (1) through a response surface method or an orthogonal test method, with respect to a specific sludge, performing optimization on a dosage of a chemical conditioner added into the specific sludge by taking an organic matter content of the specific sludge as a reference to obtain an optimal dosage of the chemical conditioner when the specific sludge has an optimal dewatering effect, so as to obtain an optimal dosage proportion of the chemical conditioner corresponding to unit mass of organic matter; the organic matter content of the specific sludge is 20 to 70%; (2) according to the optimal dosage proportion of the chemical conditioner corresponding to unit mass of organic matter obtained in the step (1), calculating an optimal dosage of the chemical conditioner applicable for other sludge to be treated, such that an optimal dosage proportion of the chemical conditioner corresponding to unit mass of organic matter for the sludge to be treated is in correspondence with the optimal dosage proportion of the chemical conditioner corresponding to unit mass of organic matter obtained in the step (1), the sludge to be treated is a municipal sludge; and (3) according to the optimal dosage of the chemical conditioner applicable for the sludge to be treated calculated in the step (2), adding the chemical conditioner to the sludge to be treated for sludge conditioning treatment, and then performing mechanical dewatering treatment, so as to obtain a deeply dewatered sludge with a moisture content of less than 60%, wherein the chemical conditioner is a composite conditioner composed of oxidation reagent and skeleton builder; the oxidation reagent in the chemical conditioner includes at least one of Fenton reagent, persulfate conditioner, permanganate and zero-valent iron conditioner for generating oxidizing groups to destroy sludge flocs to be treated so as to release the bound water; and the skeleton builder in the chemical conditioner includes at least one of lime, fly ash, diatomaceous earth, phosphogypsum and cement; the composite conditioner includes three components, two of which are oxidation reagents and one of which is a skeleton builder; dosages of the two oxidation reagents are respectively 100.15 to 271 mg/g organic matter and 49 to 123 mg/g organic matter, and a dosage of the skeleton builder is 110 to 935 mg/g organic matter.

2. (canceled)

3. (canceled)

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0022] FIG. 1 is a schematic diagram showing the binding form of water in the sludge; and

[0023] FIG. 2 is a diagram showing a relationship between organic matter content (VSS/TSS) and bound water content in the sludge.

DETAILED DESCRIPTION OF THE EMBODIMENTS

[0024] For clear understanding of the objectives, features and advantages of the present invention, detailed description of the present invention will be given below in conjunction with accompanying drawings and specific embodiments. It should be noted that the embodiments described herein are only meant to explain the present invention, and not to limit the scope of the present invention. Furthermore, the technical features related to the embodiments of the invention described below can be mutually combined if they are not found to be mutually exclusive.

[0025] According to embodiments of the present invention, there is provided a dosage optimization and control method of a chemical conditioner for deeply dewatering the sludge based on sludge organic matter content. The dosage of the chemical conditioner optimized by the method is matched with the organic matter content of the sludge, and the chemical conditioner can fully destroy the EPS structure of the sludge floc, thereby releasing the bound water and reducing the compressibility of the organic matter. Thus, this method has good adaptability to sludges with different volatile component contents. The dosage optimization and control method of cell-breaking reagents for deeply dewatering the sludge comprises the following steps:

[0026] S1: through the response surface method, the orthogonal test method and other optimization methods, performing, with respect to a specific sludge with a moderate organic matter content, optimization on the dosage of the chemical conditioner in units of milligrams per gram (mg/g organic matter mass), that is, conditioner dosage per unit mass of organic matter, so as to obtain a dosage optimization formula of the chemical conditioner for a certain sludge;

[0027] S2: according to the dosage optimization formula obtained in step S1, calculating the organic matter content of the sludge with a different organic matter content to obtain a dosage optimization formula of the chemical conditioner suitable for the sludge with such an organic matter content; and

[0028] S3: performing dosage control by using the dosage optimization formula of the chemical conditioner based on organic matter content, sludge conditioning and mechanical dewatering treatment to obtain a deeply dewatered sludge with a moisture content of less than 60%.

[0029] Specifically, in the above step S1, the sludge may be selected from municipal sludges with different properties at different times and different places. In order to make the result optimized in the step S1 more representative, a municipal sludge with an organic matter content of about 40% is preferably selected as an experimental object for conditioner dosage optimization.

[0030] In the step S1, the chemical conditioner for deep dewatering of the sludge is a composite conditioner composed of oxidation reagent and skeleton builder, in which the oxidation reagent is one of Fenton reagent, persulfate conditioner, permanganate, zero-valent iron conditioner and the like or a combination thereof, and the skeleton builder is a reagent with inorganic matter as the main component, including lime, fly ash, diatomaceous earth, phosphogypsum, cement and the like.

[0031] In the embodiments of the present invention, a composite conditioner composed of oxidation reagent and skeleton builder is used to perform conditioner dosage optimization treatment based on sludge organic matter content, achieving the following two effects:

[0032] (1) the optimization method is adapted to sludges with different organic matter contents, thereby overcoming the limitation that traditional optimization methods based on sludge dry basis (mg/g DS, or % DS) and sludge volume (percentage % by volume, or mg/L) have good conditioning effect on only a specific sludge.

[0033] (2) the composite conditioner composed of oxidation reagent and skeleton builder can be used as a cell breaking reagent to maintain pH of the dewatered filtrate of sludges with different qualities to be 6 to 7, so that the filtrate can be directly refluxed to a biological tank of the wastewater plant or used as a carbon source to strengthen the process of nitrogen and phosphorus removal from wastewater to avoid secondary pollution, while avoiding corrosion of pipes and equipment; meanwhile, the skeleton builder can improve the compressibility of the sludge cake, maintain the flow path of the filtrate, and improve the dewatering efficiency. In addition, the dosage optimization method of the chemical conditioner for deeply dewatering the sludge has a simple process, greatly improves the utilization rate of the conditioner, reduces a large amount of conditioner dosage optimization work, and thus can achieve effective disposal of the sludge in deep dewatering.

[0034] The present invention will now be further described in detail by taking the conditioner dosage optimization process and control method based on sludge organic matter content as an example, in which a composite conditioner composed of oxidation reagent and skeleton builder is used as a chemical conditioner for deeply dewatering the sludge.

Embodiment 1

[0035] In this embodiment, effects of a conditioner dosage control method based on sludge organic matter content and a conditioner dosage method based on sludge dry basis are compared, and the steps are as follows:

[0036] S1: a municipal sludge with a moderate organic matter content was selected as an object. The organic matter content of the municipal sludge in Wuhan city is about 20% to 60%, and a municipal sludge with an organic matter content of 44% was representatively selected. Through the response surface method, with respect to a sludge with a specific organic matter content, optimization on dosages of three components (wherein two are oxidation reagents, and one is a skeleton builder) of the composite conditioner composed of oxidation reagent and skeleton builder in units of milligrams per gram (mg/g organic matter mass) was performed to obtain a conditioner dosage optimization formula for this sludge: dosages of a cell breaking reagent A1, a cell breaking reagent B1 and a skeleton reagent C1 are 106.91, 86.16 and 110.00, respectively (mg/g organic matter mass);

[0037] S2: according to the optimization formula obtained in the step S1, with respect to a sludge with a different organic matter content, the dosage of the conditioner was calculated based on sludge organic matter content to obtain a composite conditioner optimization formula for the sludge with the organic matter content.

[0038] In this embodiment, sludges with different organic matter contents were taken from four different wastewater treatment plants (WWTP) for verification test. The organic matter contents of the sludges from these wastewater treatment plants are 25.6%, 41.20%, 49.67% and 59.83%, respectively.

[0039] Dosages of the conditioner calculated based on different sludge organic matter masses are shown in Table 1 below:

TABLE-US-00001 TABLE 1 Conditioner dosage calculated Organic based on organic matter Organic Sludge matter Cell matter dry mass in breaking Skeleton content basis sludge reagent Reagent reagent Source (%) (kg) (kg) A1 (g) B1 (g) C1 (g) WWTP1 25.60 0.7 0.18 19.24 15.51 20 WWTP2 41.20 0.7 0.29 31.00 24.99 32 WWTP3 49.67 0.7 0.35 37.42 30.16 38 WWTP4 59.83 0.7 0.42 44.90 36.19 46

[0040] At the same time, in order to make a comparison with the conditioner dosage control method based on sludge dry basis (mg/g DS), the conditioner was added according to the optimization formula based on sludge dry basis in combination with the result optimized in the step S1. Dosages of the conditioner calculated based on sludge dry basis are shown in Table 2 below:

TABLE-US-00002 TABLE 2 Conditioner dosage calculated Organic based on DS Organic Sludge matter Cell matter dry mass in breaking Skeleton content basis sludge reagent Reagent reagent Source (%) (kg) (kg) A1 (g) B1 (g) C1 (g) WWTP1 25.60 0.7 0.18 32.93 26.54 34 WWTP2 41.20 0.7 0.29 32.93 26.54 34 WWTP3 49.67 0.7 0.35 32.93 26.54 34 WWTP4 59.83 0.7 0.42 32.93 26.54 34

[0041] S3: sludge dewatering treatment: after the two conditioner dosage methods were respectively used to perform sludge conditioning, mechanical dewatering treatment was performed (filtration pressure: 0.8 MPa, diaphragm pressing pressure: 1.2 MPa).

[0042] The tests showed that after the conditioned sludges were dewatered by plate-frame pressure filtration, moisture contents of the sludge cakes obtained by the two conditioner dosage methods are shown in Table 3 below:

TABLE-US-00003 TABLE 3 Organic Moisture content of dewatered sludge cake (%) matter Method based on sludge Method based on Source content (%) organic matter content sludge dry basis (DS) WWTP1 25.60% 44.27 45.23 WWTP2 41.20% 51.80 52.54 WWTP3 49.67% 56.31 58.22 WWTP4 59.83% 59.71 63.02

[0043] It is obvious from the above results that the optimization method of the present invention adopting the composite conditioner composed of oxidation reagent and skeleton builder can be well adapted to sludges with different organic matter contents. With the optimization method, the sludge dewatering effect can be obviously improved for a sludge with high organic matter content, and for a sludge with low organic matter content, the dewatering effect equivalent to that of the traditional dosage method is ensured while greatly reducing dosages of reagents.

Embodiment 2

[0044] In this embodiment, the adaptability of the optimization formula, which is obtained by the conditioner dosage control method based on sludge organic matter content, to sludges with different organic matter contents is verified, and steps are as follows:

[0045] S1: through the response surface method, with respect to a sludge with an organic matter content of 42.8%, dosage optimization of the composite conditioner composed of oxidation reagent and skeleton builder was performed to obtain a composite conditioner dosage optimization formula based on unit mass of organic matter for this sludge: dosages of a cell breaking reagent A2 is 271 (mg/g organic matter mass), a cell breaking reagent B2 is 49 (mg/g organic matter mass), and a skeleton reagent C2 is 935 (mg/g organic matter mass);

[0046] S2: similarly, through the response surface method, with respect to a sludge with an organic matter content of 49.8%, dosage optimization of the composite conditioner was performed to obtain a composite conditioner dosage optimization formula based on unit mass of organic matter for this sludge: dosages of a cell breaking reagent A2 is 269 (mg/g organic matter mass), a cell breaking reagent B2 is 49 (mg/g organic matter mass), and a skeleton reagent C2 is 872 (mg/g organic matter mass).

[0047] It is obvious from the above results that compared with the cases where the traditional optimization methods based on sludge dry basis (mg/g DS) and sludge volume (percentage % by volume, or mg/L) have great difference in optimal results of dosages of the conditioner for different sludges, optimal dosages of the composite conditioner composed of oxidation reagent and skeleton builder optimized by the method of the present invention are very close, regardless of sludge organic matter content, indicating that the method of the present invention can be well adapted to sludges with different organic matter contents.

Embodiment 3

[0048] In this embodiment, with respect to the composite conditioner for deeply dewatering different sludges, the conditioner dosage control method based on unit mass of organic matter is verified, and steps are as follows:

[0049] S1: a municipal sludge with moderate organic matter content was selected as an object, and in this embodiment, a municipal sludge with an organic matter content of 53.73% was representatively selected. Through the response surface method, with respect to a sludge with a organic matter content of 53.73%, optimization on the dosage of the composite conditioner composed of oxidation reagent and skeleton builder in units of milligrams per gram (mg/g organic matter mass) was performed to obtain an dosage optimization formula of the three components of the composite conditioner for deeply dewatering this sludge: dosages of a cell breaking reagent A3, a cell breaking reagent B3 and a skeleton reagent C3 are 100.15 (mg/g organic matter mass), 123.00 (mg/g organic matter mass), and 650.00 (mg/g organic matter mass), respectively;

[0050] S2: according to the optimization formula obtained in the step S1, with respect to a sludge with a different organic matter content, the dosage of the conditioner was calculated based on unit mass of organic matter to obtain a composite conditioner optimization formula for deeply dewatering the sludge with the organic matter content.

[0051] Sludges with different organic matter contents in different wastewater treatment plants can be tested, and in this embodiment, a sludge with an organic matter content of 46.14% is selected for testing.

[0052] The dosage of the conditioner calculated based on sludge organic matter content is shown in Table 4 below:

TABLE-US-00004 TABLE 4 Conditioner dosage calculated Organic based on organic matter content Organic Sludge matter Cell matter dry mass in breaking Skeleton content basis sludge reagent Reagent reagent Source (%) (kg) (kg) A3 (g) B3 (g) C3 (g) WWTPa 46.14 0.4 0.18 18.027 22.14 117

[0053] At the same time, in order to make a comparison with the conditioner dosage method based on sludge dry basis (mg/g DS), the conditioner was added according to the optimization formula based on sludge dry basis in combination with the result optimized in the step S1. The dosage of the conditioner calculated based on sludge dry basis is shown in Table 5 below:

TABLE-US-00005 TABLE 5 Conditioner dosage calculated Organic based on DS Organic Sludge matter Cell matter dry mass in breaking Skeleton content basis sludge reagent Reagent reagent Source (%) (kg) (kg) A3 (g) B3 (g) C3 (g) WWTPa 46.14 0.4 0.18 21.524 26.435 139.70

[0054] S3: sludge dewatering treatment: after the two conditioner dosage methods were respectively used to perform sludge conditioning, mechanical dewatering treatment was performed (filtration pressure: 0.8 MPa, diaphragm pressing pressure: 1.2 MPa).

[0055] The tests showed that after the conditioned sludges were dewatered by plate-frame pressure filtration, moisture contents of the sludge cakes obtained by the two conditioner dosage methods are shown in Table 6 below:

TABLE-US-00006 TABLE 6 Organic matter Moisture content of deeply dewatered sludge cake (%) content Method based on sludge Method based on sludge Source (%) organic matter content dry basis (DS) WWTPa 46.14% 52.53 53.41.

[0056] It is obvious from the above results that the optimization method of the present invention adopting the composite conditioner composed of oxidation reagent and skeleton builder can be well adapted to sludges with different organic matter contents. For the raw sludge with the same quality, the sludge dewatering effect can be obviously improved for a sludge with high organic matter content, and for a sludge with low organic matter content, the dewatering effect equivalent to that of the traditional dosage method is ensured, while greatly reducing dosages of reagents.

[0057] In the actual project, the optimization of the deep dewatering conditioner for destroying the organic floc structure of the sludge only needs to be performed for a representative sludge, and then optimal dosages of the conditioner adapted for different sludges can be calculated according to volatile component contents of the different sludges, which results in greatly saved number and cost of optimization experiments, simple operation and good effect, and lays the foundation for the engineering practice of deep dewatering of the sludge.

[0058] The optimization methods such as the response surface method and the orthogonal test method in the present invention can be directly referred to the related prior art, for example, the literature published by Tony et al. in Chemosphere 2008, 72, (4), 673-677.

[0059] In a dosage optimization method of a chemical conditioner for deeply dewatering the sludge in the present invention, the optimal dosage of the chemical conditioner is calculated based on the organic matter content of the sludge to be treated, and the organic matter content can be measured according to the standard method in solid waste determination of organic matter in national environmental protection standards HJ 761-2015.

[0060] It should be readily understood to those skilled in the art that the above description is only preferred embodiments of the present invention, and does not limit the scope of the present invention. Any change, equivalent substitution and modification made without departing from the spirit and scope of the present invention should be included within the scope of the protection of the present invention.