Research on the Cotreatment of Landfill Leachate with

Ozone and Electromagnetic Technology

Z S Wang

1, 2, 3, *,

Z Y Jiang

1, 2, 3

, M C Chi

and T Y He

State Key Laboratory of Biobased Material and Green Papermaking, Qilu

University of Technology, Shandong Academy of Sciences, Jinan, 250353

Key Laboratory of Pulp & Paper Science and Technology of Education Ministry of

China, Jinan, 250353

College of Paper and Plant Resources Engineering, Qilu University of Technology

(Shandong Academy of Sciences), 3501 Daxue Rd, Changqing district, Jinan city,

Shandong Province, P.R.China

Corresponding author and e-mail: Z S Wang, wzsylq@aliyun.com

Abstract. The optimum technological conditions were investigated and the removal rates of

BOD (BOD

), COD, SS and AN (Ammonia Nitrogen) were obtained by using the ozone

generator and electromagnetic technology to treat municipal landfill leachate. These results

showed that the removal rates of BOD, COD, SS and AN reached to 83.7%, 53.1%, 85.4%

and 57.8% using ozone generator to treat them for 90 min respectively. Subsequently, the

treatment of municipal landfill leachate was continuously treated via graphite electromagnetic

device. The result exhibited that the optimal treatment condition was as follows: voltage 9.2

V, current 1.72 A, the number of graphite plates in series 10, plate distance 3.24 mm and the

treatment time 25 min. The removal rates of BOD, COD, SS and AN were 89.9%, 76.0%,

89.3% and 78.8%, respectively in this condition.

1. Introduction

Landfill leachate is a kind of high concentration wastewater with high pollution and complex

composition. It mainly comes from the water contained in the garbage, the precipitation of the

landfill and the moisture were produced by the pollutants in the landfill due to the compaction and

microbial decomposition [1]. Landfill leachate has complex composition, usually is dark black with a

certain irritating smell. The landfill leachate consists of inorganic pollutants (such as heavy metal

ions, inorganic salts, and so on), organic pollutants (such as high concentration organic acids, alcohol

and other organic waste liquid, etc.) and microbes (colibacillus and other harmful microorganisms,

etc.)[2].

Ozone is a strong oxidant with oxidation potential of 2.07 V. Ozone has the characteristics of quick

reaction with organic matter without secondary pollution, local production, easy availability of raw

materials and convenient use [3]. Ozone can react with soluble and insoluble pollutants in water to

convert complex organic matter into simple organic matter, and changes the polarity, biodegradability and

toxicity of pollutants, and greatly reduces COD, BOD, SS and AN (Ammonia Nitrogen, the same below)

Wang, Z., Jiang, Z., Chi, M. and He, T.

Research on the Cotreatment of Landﬁll Leachate with Ozone and Electromagnetic Technology.

In Proceedings of the International Workshop on Environmental Management, Science and Engineering (IWEMSE 2018), pages 409-415

ISBN: 978-989-758-344-5

409

in water. Excess ozone can be decomposed into oxygen by itself. Ozone wastewater treatment is an

effective, environmental-friendly and energy-saving method [4].

During the treatment of wastewater, the basic principle of electrolysis and electromagnetism is that the

harmful substances in the wastewater are enriched on both anode and cathode, subsequently, they are

oxidated and reduced, respectively, thereby converting them into harmless substances or separating

and concentrating them to achieve the purification and separation of wastewater [5].

Graphite electrode was considered as a good electromagnetic sewage treatment electrode selection

with long service life due to its excellent electrical conductivity, high temperature resistance, chemical

corrosion resistance, excellent chemical stability [6].

In this paper, the landfill leachate was treated via the ozone and optimized the treatment process.

In order to further treat sewage, the electromagnetic technology was firstly proposed to continuously

deal with the above sewage, leading to the further reduction of the COD , BOD, SS and AN in waste

water and reach to the wastewater discharge standard, thereby realizing the sewage reuse.

2. Experiment

2.1. Experimental instruments and chemicals

Electric drying oven with forced convection (DHG-9140A,Gongyi Yuhua instruments co., Ltd.);

BOD detector (LH-BOD601A, Lianhua Technology); Energy saving COD constant temperature

heater (JHR-2, Shanghai Yetuo instrument Co., Ltd.); UV-Vis Spectrophotometer (Agilent, USA);

Ozone generator (Qingdao ODO environmental technology development Co., Ltd); Slag water

separator (self-made). Municipal landfill leachate from the Qihe refuse treatment plant. Potassium

dichromate digestion solution (self-made); Potassium sodium tartrate standard solution (self-made);

Nessler's reagent (self-made).

2.2. Experimental method

2.2.1. Ozone treatment method. The volume of waste water used in the experiment is 22, 000 mL.

The wastewater was treated by ozone and electromagnetic cooperation, and ozone was first used for

1.5 hours. The experimental process of ozone wastewater treatment is shown in Figure 1.

Figure 1. The experimental flow chart of ozone wastewater treatment.

2.2.2. Electromagnetic treatment method. The graphite plate with microporous structure is used as

electrode in this experiment, which provides a large specific surface area and a uniform flow channel,

IWEMSE 2018 - International Workshop on Environmental Management, Science and Engineering

410

and provides a greater current density and better catalytic reaction effect for wastewater treatment. A

special graphite electrode plate is used to recycle the wastewater sample. The experimental device is

shown in Figure 2.

By changing the variables such as current and voltage, distance between electrode plates and reaction

time, the effects of these factors on the treatment of wastewater by electromagnetic technology were

researched, and the optimum technological conditions were obtained.

Figure 2. The diagram of the experimental equipment for electromagnetic processing.

3. Results and discussions

3.1. Ozone treatment process

Ozone water was prepared by using the purchased ozone generator. The ozone concentration of

ozone water was determined by KI-Na

method and the value was 14.4 ppm. The waste leachate

was treated by ozone generator, and the curves of COD, BOD (BOD

, the same below), SS and AN

with the treatment time were shown in Figure 3.

Figure 3. The variation curves of COD, BOD, SS and AN with ozone treatment time.

As shown in Figure 3, the COD, BOD, SS and AN of landfill leachate decreased with the

enhancement of ozone treatment time. After 90 min, it was reduced 83.7%, 52.5%, 85.4% and 57.8%

Research on the Cotreatment of Landﬁll Leachate with Ozone and Electromagnetic Technology

411

from 486mg/L,1323mg/L,171g/L,45mg/L to 79mg/L, 629mg/L, 25g/L, 19mg/L respectively.

Obviously, the reduction of BOD and SS after ozone treatment was much larger than that of 80%,

while the decrease of COD and AN was about 50%. The result indicated that ozone treatment has

obvious effect on organic pollutants in sewage.

3.2. Electromagnetic treatment process

Further treatment of waste leachate treated by ozone using electromagnetic device:

(1) The control voltage was 5.1 V, the current was 0.74 A, 2 pieces of graphite plate and the distance

between the graphite plates was 1.08mm (between the two plates was a layer of insulation net). The curve

of the change of the control voltage with the treatment time was shown in Figure 4.

It could be observed in Figure 4, in 0-30 minutes, the COD, BOD, SS and AN of the leachate have a

decreasing tendency with the increase of the electromagnetic processing time. Before processed, the

amount of BOD, COD, SS, AN was 79 mg/L, 629 mg/L, 25g/L and 19 mg/L, respectively. And after 30

minutes, it went down to 65mg/L, 565 mg/L, 17g/L, 12mg/L, reduced to 17.7%, 10.2, 32.0%, 36.8%

respectively. It was obvious that the reduction of BOD and COD was not significant after electromagnetic

treatment, while the decrease of SS and AN was more than 30%. It can be found that the more suitable

electromagnetic treatment time was 25 min.

Figure 4. The curves of the changes of COD, BOD, SS and AN with time.

(2) Control voltage 5.1 v, current 0.74 A，2 graphite plates, treatment time 25 min, change the

electrode plate distance. The curves of the changes of COD, BOD, SS and AN with plate distance are

shown in Figure 5.

(3) In the Figure 5, it can be seen that with the increase of plate distance, the index value of

sewage decreases slowly but the change is very slight. The result suggested that the distance between

electrodes has no great effect on the treatment of electromagnetic sewage.

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Figure 5. The curves of the changes of BOD，COD，SS and AN with plate distance.

(4) Control voltage 5.1V, current 0.74A, graphite plate distance 3.24 mm, reaction time 25 min.

The effect of the number of electrode plates on sewage treatment was also studied, and the result was

shown in Table 1.

As shown in table 1, with the increase of the number of graphite electrode plate, sewage BOD,

COD, SS, AN were reduced, and the removal effect was most obvious when the number increased to

10. Continuously increasing the number of electrode plates, almost no significant changes have been

observed in Table 1. Therefore, the optimum number of electrode plates for electromagnetic

treatment under this condition was determined to be 10.

Table 1. The effect of the number of electrode plates on sewage treatment.

The number of

electrode plates

BOD

COD

629

519

507

496

480

482

20.9

20.5

19.8

18.3

(5) Controlling the distance of graphite electrode plate to 3.24 mm, the number of graphite plate

10, the processing time 25 min. By adjusting the voltage and current, the variation of each

performance index is determined. The curves of the changes of COD, BOD, SS and AN with voltage

and current were shown in Figure 6.

Research on the Cotreatment of Landﬁll Leachate with Ozone and Electromagnetic Technology

413

Figure 6. The effect of voltage/current on sewage treatment.

It was clear in Figure 6 that when the voltage varied from 5V to 10V, with the increase of rated

voltage and current, the value of BOD and COD of the wastewater decreased from 51mg/L and

480mg/L to 49mg/L and 457 mg/L, which decreased by 3.9% and 4.8% respectively, while SS and

AN have no change. When the voltage was between 10 and 30 v, with the increase of rated voltage

and current, the BOD, COD, AN and SS of waste water increases, and the voltage of 29.3V is

increased by 6.1% , 3.9%, 1.6% and 16.7% respectively, compared with the voltage of 9.2V. This

result showed that under the above conditions, the electrified voltage/current of sewage treatment

was the best choice at 9.2V/1.72A.

(6) Under the experimental conditions, the landfill leachate was treated with ozone generator for

90 minutes, then control the voltage at 9.2 V, the current at 1.72 A, the number of electrode plates is

10, and the electromagnetic technique is used for 25 minutes.The experimental data of ozonic-

electromagnetic treatment of landfill leachate is shown in table 2. As can be seen from table 2, the

BOD, COD, SS and AN of landfill leachate decreased to 49mg/L, 317mg/L, 18.3g/L, and 49mg/L

from pretreatment 486mg/L, 1323mg/L, 171g/L and 45mg/L, and the removal rates were 89.9%,

76%, 89.3% and 77.8% respectively, and the treatment effect is good.

Table 2. The experimental data of ozonic-electromagnetic treatment of landfill leachate.

BOD（ mg/L）

COD（ mg/L）

SS（ g/L）

AN（ mg/L）

Before treatment

486

1323

171

After ozone treatment

629

Reduced %

83.7

52.5

85.4

57.8

After ozonic -

electromagnetic

treatment

317

18.3

Reduced %

89.9

76.0

89.3

77.8

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4. Conclusions

The composition of landfill leachate was complex and was difficult to deal with them via the

conventional biochemical technology. However, good results have been achieved by using ozone-

electromagnetic technology. After being treated for 90 min via ozone generator, the experimental

results showed that the removal rates of BOD, COD, SS and AN reached to 83.7%, 53.1%, 85.4%

and 57.8%, respectively. Subsequently, the municipal sewage was continuously treated by graphite

electromagnetic technology. The optimal treatment conditions were as follows: voltage 9.2 V, current

1.72 A, and the number of graphite plates in series 10, the plate distance 3.24 mm, the cycle

treatment time for 25 min, the removal rates of BOD, COD, SS and AN reached to 89.9%, 76.0%,

89.3% and 77.8% respectively. This work demonstrated the the cotreatment both ozone treatment and

electromagnetic technology may offer an attractive approach for the the purification and separation

of wastewater.

Acknowledgement

The project supported by the Foundation (No.ZR201706) of Key Laboratory of Pulp and Paper

Science and Technology of Ministry of Education/Shandong Province of China. The authors are

grateful for the financial support from the National Key Research and Development Program of

China (Grant No. 2017YFB0307900), the National Natural Science Foundation of China (Grant No.

31470602, 31670595, 31770628), the Provincial Key Research and Development Program of

Shandong (Grant No. 2016CYJS07A01) and the Taishan Scholars Program.

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