CN102126818A - Chlorine dioxide/ultrasonic wave-coupled excess sludge decrement pretreating method - Google Patents

Abstract

The present invention is a chlorine dioxide/ultrasonic coupling residual sludge reduction pretreatment method, which firstly performs chlorine dioxide treatment on the residual sludge generated in the secondary biological sewage treatment process, and then performs ultrasonic treatment: chlorine dioxide The treatment is to add chlorine dioxide to the sludge liquid, stir with an electromagnetic stirrer, the rotation speed is 60-100r/min, the dosage of chlorine dioxide per gram of dry sludge is 2-6mg, and the treatment time is 60-90min; Treatment: Ultrasonic treatment is performed on the sludge treated with chlorine dioxide, the ultrasonic sound energy density is 0.5-1.0W/mL, the ultrasonic action time is 2-6min, and the ultrasonic frequency is 20-40kHz. Compared with chlorine dioxide or ultrasonic treatment alone, the invention improves sludge treatment efficiency, reduces energy consumption by 3-20%, reduces treatment cost, and is suitable for sludge reduction treatment in sewage treatment plants.

Description

A Chlorine Dioxide/Ultrasonic Coupled Excess Sludge Reduction Pretreatment Method

technical field

The invention relates to a pretreatment method for reducing the amount of excess sludge in a sewage treatment plant, in particular to a two

Chlorine Oxidation/Ultrasonic Coupled Pretreatment Method for Excess Sludge Reduction.

Background technique

Since the activated sludge method was applied to sewage treatment in the early 20th century, it has become the most widely used sewage treatment process in the world. Up to now, more than 90% of the municipal sewage treatment in the world has adopted the activated sludge method. However, the activated sludge method will produce a large amount of excess sludge: due to the metabolism and biosynthesis of microorganisms, the biomass of activated sludge in the aeration tank increases, and part of the sludge settled in the secondary sedimentation tank is returned to the aeration tank. The pool is used for reprocessing sewage, and the excess is discharged out of the system, that is, residual sludge. With the popularization of sewage treatment, the production of surplus sludge is increasing day by day. The excess sludge has a high moisture content and contains a considerable amount of harmful substances (such as viruses, pathogenic bacteria, parasite eggs and heavy metals, etc.) and unstabilized organic matter. It is difficult to dehydrate and stabilize, and the treatment cost is high. cause secondary pollution. The treatment and disposal of excess sludge has emerged as an urgent problem to be solved in urban sewage treatment.

The pretreatment technology of excess sludge is one of the keys to realize sludge reduction, stabilization and harmlessness. Existing pretreatment methods for surplus sludge mainly include ultrasonic wave, heat treatment, acidification, alkaline hydrolysis, ozone, chlorine gas, etc.

As a sludge pretreatment technology, the sludge is treated by ozone oxidation, which has a significant reduction effect, but it will cause a decrease in the removal efficiency of N and P in the subsequent system. In addition, the cost of sludge reduction by the ozone method is high, and the power consumption per unit of ozone reaches 20-25KWh/kgO ₃ only in the production of ozone, which is difficult to apply on a large scale. Although chlorine gas oxidation is cheaper than ozone, the use of chlorine gas treatment will deteriorate the sludge settling performance, increase the COD of the effluent, and the sludge is more likely to generate foam, which has the potential danger of producing carcinogenic THMs. Ultrasonic treatment can not only reduce the amount of sludge, but also effectively improve the sedimentation performance of sludge. However, to achieve the desired effect, the energy consumption is relatively high, which limits its popularization and application. Using heat, acid and alkali treatment, the process control is complicated, and it is highly corrosive to the equipment.

Contents of the invention

The main purpose of the present invention is to overcome the shortcomings of low efficiency or high energy consumption of pretreatment of residual sludge with chlorine dioxide or ultrasonic waves alone in the prior art, and provide a chlorine dioxide with high treatment efficiency and relatively low energy consumption. /Ultrasonic coupled excess sludge reduction pretreatment method.

In the present invention, the oxidation reaction between chlorine dioxide and the microbial cells in the sludge causes some microbial cell walls to rupture, allowing the intracellular substances to enter the water from the solid phase. At the same time, due to the strong oxidation of chlorine dioxide, the microbial cells At the same time, it can also separate a part of the inorganic components adsorbed in the sludge body or surface from the solid phase of the sludge. Then, the treatment with higher sound energy density and shorter time not only strengthens the damage to the cell wall structure, but also partially destroys the sludge cells, and strengthens the degree and effect of cracking.

The purpose of the invention is through the following technical solutions:

A chlorine dioxide/ultrasonic coupling residual sludge reduction pretreatment method, the residual sludge generated in the secondary biological sewage treatment process is first treated with chlorine dioxide, and then ultrasonically treated, including the following steps:

(1) Chlorine dioxide treatment: Dosing chlorine dioxide in the sludge liquid, stirring with an electromagnetic stirrer, the rotation speed is 60-100r/min, and the dosage of chlorine dioxide per gram of dry sludge is 2-6mg. Time 60-90min;

(2) Ultrasonic treatment: Ultrasonic treatment is performed on the sludge treated with chlorine dioxide, the ultrasonic sound energy density is 0.5-1.0W/mL, the ultrasonic action time is 2-6min, and the ultrasonic frequency is 20-40kHz.

To further realize the object of the present invention, the excess sludge produced in the secondary biological sewage treatment process refers to the sludge produced after the SBR system treatment.

The sonication is carried out by ultrasonic cell pulverizer.

The sludge treated with chlorine dioxide is subjected to ultrasonic treatment, the ultrasonic sound energy density is 0.5-1.0W/mL, the ultrasonic action time is 2-6min, and the ultrasonic frequency is 20-40kHz.

Part or all of the sludge after ultrasonic treatment is returned to the secondary biological treatment system for digestion and weight reduction.

Compared with prior art, the present invention has following advantage:

For the first time in the present invention, chlorine dioxide/ultrasonic coupling is used for residual sludge pretreatment. On the one hand, the low cost of chlorine dioxide is utilized, and the sludge concentration is kept uniform by stirring, which compensates for the impact of sludge solids on ultrasonic waves to a certain extent. The impact in sludge transmission saves energy consumption and improves efficiency. On the other hand, in view of the possible deterioration of sedimentation performance after oxidative lysis of chlorine dioxide and the deterioration of water quality after treatment, ultrasonic treatment can effectively improve water quality. After treatment, the soluble COD of the supernatant increased by 400-1800%, the TN increased by 60-170%, and the TP increased by 200-400%. Compared with the single use of chlorine dioxide or ultrasonic treatment, the sludge treatment efficiency is improved, the energy consumption is reduced by 3-20%, and the treatment cost is reduced. It is suitable for the treatment of excess sludge in sewage treatment plants, and can be used for pretreatment of sludge to produce agricultural fertilizers, and has broad application prospects.

specific implementation plan

The present invention will be further described below in conjunction with the examples, but the embodiments of the present invention are not limited thereto.

Example 1:

SBR pilot test system (sequential batch activated sludge process) of a sewage treatment plant in Foshan City, the main device is a 1.5×1.2×0.9m SBR reactor with an effective volume of 1260L, and the operation cycle is 8 hours in total, divided into 5 stages: water inflow (0.5h), aeration (4h), sedimentation (1.5h), drainage (0.5h), idle (1.5h). Discharge mud about 135-200g per cycle. After testing, the properties of the remaining sludge are as follows: the sludge concentration is about 10-20g/L, the soluble COD is 30.02mg/L, the TN is 13.44mg/L, the TP is 2.01mg/L, and the pH is 7.8. Take 1L of sludge liquid in a container, add chlorine dioxide at 2 mg/g of dry sludge, stir with an electromagnetic stirrer, and react for 1 hour under stirring at a speed of 60 r/min, and then perform ultrasonic treatment in an ultrasonic cell pulverizer at an ultrasonic frequency of 20 ~40kHz, ultrasonic sound energy density 0.5W/mL, ultrasonic time 2min. After treatment, the soluble COD of the supernatant increased by 411.66%, TN increased by 59.78%, and TP increased by 204.19%. The energy consumption was 4.50% lower than that of chlorine dioxide alone and 6.58% lower than that of ultrasonic treatment alone under the same effect conditions.

Example 2:

The SBR pilot system of a sewage treatment plant in Foshan City, the main device is a 1.5×1.2×0.9m SBR reactor, the effective volume is 1260L, the operation cycle is 8h, and it is divided into 5 stages: water intake (0.5h), aeration (4h ), sedimentation (1.5h), drainage (0.5h), idle (1.5h). Discharge mud about 135-200g per cycle. After testing, the properties of the remaining sludge are as follows: the sludge concentration is about 10-20g/L, the soluble COD is 25.6mg/L, the TN is 12.5mg/L, the TP is 1.46mg/L, and the pH is 7.05. Take 1L of sludge liquid in a container, add chlorine dioxide at 4 mg/g of dry mud, stir with an electromagnetic stirrer, and react for 1 hour under stirring at a speed of 80 r/min, and then perform ultrasonic treatment in an ultrasonic cell pulverizer at an ultrasonic frequency of 20 ~40kHz, ultrasonic sound energy density 0.5W/mL, ultrasonic time 6min. After treatment, the soluble COD of the supernatant increased by 787.5%, TN increased by 94.6%, and TP increased by 245.19%. The energy consumption was 5.74% lower than that of chlorine dioxide alone and 8.21% lower than that of ultrasonic treatment alone under the same effect.

Example 3:

The SBR pilot system of a sewage treatment plant in Foshan City, the main device is a 1.5×1.2×0.9m SBR reactor, the effective volume is 1260L, the operation cycle is 8 hours, and it is divided into 5 stages: water intake (0.5h), aeration (4h ), sedimentation (1.5h), drainage (0.5h), idle (1.5h). Discharge mud about 135-200g per cycle. After testing, the properties of the remaining sludge are as follows: the sludge concentration is about 10-20g/L, the soluble COD is 20.15mg/L, the TN is 19.53mg/L, the TP is 3.41mg/L, and the pH is 7.21. Take 1L of sludge liquid in a container, add chlorine dioxide at 2 mg/g of dry sludge, stir with an electromagnetic stirrer, and react for 1 hour under stirring at a speed of 60 r/min, and then perform ultrasonic treatment in an ultrasonic cell pulverizer at an ultrasonic frequency of 20 ~40kHz, ultrasonic sound energy density 1W/mL, ultrasonic time 4min. The soluble COD in the treated sludge increased by 1093.67%, TN increased by 112.6%, and TP increased by 270.05%. The energy consumption was 2.78% lower than that of chlorine dioxide alone and 14.2% lower than that of ultrasonic treatment alone under the same effect conditions.

Example 4:

The SBR pilot system of a sewage treatment plant in Foshan City, the main device is a 1.5×1.2×0.9m SBR reactor, the effective volume is 1260L, the operation cycle is 8 hours, and it is divided into 5 stages: water intake (0.5h), aeration (4h ), sedimentation (1.5h), drainage (0.5h), idle (1.5h). Discharge mud about 135-200g per cycle. After testing, the properties of the remaining sludge are as follows: the sludge concentration is about 10-20g/L, the soluble COD is 25.12mg/L, the TN is 15.74mg/L, the TP is 2.77mg/L, and the pH is 7.48. Take 1L of sludge liquid in a container, add chlorine dioxide at 6mg/g dry sludge, stir with an electromagnetic stirrer, and react for 1.5h under stirring at a speed of 100r/min, then perform ultrasonic treatment in an ultrasonic cell pulverizer, the ultrasonic frequency 20 ~ 40kHz, ultrasonic sound energy density 1W/mL, ultrasonic time 6min. After treatment, the soluble COD of the supernatant increased by 1836%, the TN increased by 173.04%, the TP increased by 395.75%, the biodegradability increased by 62.1%, and the energy consumption decreased by 6.98% compared with chlorine dioxide alone under the same effect conditions. 20.23% lower than that of ultrasonic treatment alone.

The above are only several specific embodiments of the present invention. Due to the different sewage treatment processes, the properties of the remaining sludge produced are different, and because the parameters and performance of the ultrasonic generator are different, the chlorine dioxide raw materials produced by different manufacturers and Concentrations are different, so some parameters of the present invention can be properly adjusted to suit specific situations without departing from the essence of the present invention and the scope of the appended claims. However, the design concept of the present invention is not limited thereto, any non-substantial changes to the present invention by using this concept should be an act of violating the protection scope of the present invention.

Claims (4)

1. dioxide peroxide/ultrasonic wave coupled excess sludge reduction pretreatment process is characterized in that, the excess sludge that produces in the two stage biological sewage treatment process is carried out chlorine dioxide treatment earlier, carries out ultrasonication again; Comprise the steps:

(1) chlorine dioxide treatment: add dioxide peroxide in excess sludge, adopt magnetic stirrer to stir, rotating speed is 60～100r/min, and every gram dewatered sludge dioxide peroxide dosage is 2～6mg, treatment time 60-90min;

(2) ultrasonication: the mud after the chlorine dioxide treatment carries out ultrasonication, and ultrasonic acoustic density is 0.5～1.0W/mL, ultrasonication time 2～6min, and ultrasonic frequency is 20～40kHz.

2. a kind of dioxide peroxide as claimed in claim 1/ultrasonic wave coupled excess sludge reduction pretreatment process, it is characterized in that: the excess sludge that produces in the described two stage biological sewage treatment process is meant the mud that produces after the SBR system handles.

3. a kind of dioxide peroxide as claimed in claim 1/ultrasonic wave coupled excess sludge reduction pretreatment process, it is characterized in that: described supersound process is to be undertaken by ultrasonic cell disruptor.

4. a kind of dioxide peroxide as claimed in claim 1/ultrasonic wave coupled excess sludge reduction pretreatment process is characterized in that: the sludge part after the ultrasonication or all be back to the two stage biological treatment system and carry out digestion decrement and handle.