In order to solve the problems of poor biodegradability and high concentrations of non-biodegradable substances from pharmaceutical wastewater after preliminary treatment, the organic components of the tail water (effluent from the preliminary treatment devises of the pharmaceutical industry wastewater treatment station) were analyzed and the method of ozonation-hydrolysis acidification was used to treat tail water from the pharmaceutical factory. The ozone dosage, the reaction time and the changes of biodegradability were studied. The results measured by GC-MS showed that there were 51 types of organic substances in tail water which reduce the biodegradability. The results of the tests showed that 30 mg/L of ozone and 60-minutes of oxidation time were suitable conditions. In the ozonation–hydrolysis acidification process the COD removal rate ranged from 20% to 50%. The test results showed that the ozonation-hydrolysis acidification method could effectively improve the biodegradability of wastewater and provide the foundation for the follow treatment in urban sewage treatment plant using biological methods.

INTRODUCTION

The presence of pharmaceuticals and personal care products (PPCPs) was first identified in surface and waste waters in the United States and Europe in the 1960s (Stumm-Zollinger & Fair 1965). PPCPs in the aquatic environment have been reported in the last few decades (Daughton & Ternes 1999). These pharmaceuticals can have serious effects on surface water resources and the purity of drinking water directly or indirectly. As the pharmaceutical wastewater includes many non-biodegradable substances, it is necessary to adopt complex processes to deal with the wastewater. Some different treatment methods reported can be used for the treatment of pharmaceutical wastewater such as physicochemical methods treatment which include screening, chlorination, coagulation/ flocculation, sedimentation, adsorption, reverse osmosis (Deegan et al. 2011), biological treatment methods (Suman Raj & Anjaneyulu 2005) and chemical oxidation methods (Khetan & Collins 2007). Biological treatment is usually combined with chemical oxidation used as a pre-treatment or post-treatment step. To completely eliminate pharmaceuticals from wastewater, the advanced oxidation methods may be required (Huber et al. 2005; Justo et al. 2013).

Because of expanded pharmaceutical products range and increased pollution components, the wastewater from the Northeast Pharmaceutical Factory of China disposed by the original anaerobic–aerobic biological process could not reach the standard of discharging to the urban sewage treatment plant using biological methods. It was necessary to improve the original process to increase the treatment efficiency. Pharmaceutical wastewater treated by the process of a pharmaceutical treatment station is usually called pharmaceutical tail water. The pharmaceutical tail water from the Northeast Pharmaceutical Factory treated by the anaerobic–aerobic biological process had the characteristics of poor biodegradability and included high concentrations of non-biodegradable substances which could not discharge to an urban sewage treatment plant using biological methods.

Ozone is a strong oxidizing agent widely used in water treatment with a high redox potential in the water (Loeb et al. 2012). Ozone oxidation and decomposition reaction is a free radical reaction, in which oxygen and hydroxyl radicals are formed through a series of reactions (Snyder et al. 2006). Hydroxyl radicals have stronger oxidation ability than oxygen and can decompose non-biodegradable substances (Janzen et al. 2011). Ozone plays a major role in wastewater treatment and thus ozonation has become a promising technology for the treatment of water and wastewater in the last few decades (Upadhyay & Shrivastava 2005). In ozonation, the ozone molecules rupture the target molecules and produce byproducts that are easily biodegradable. Ozone treatment usually improves the biodegradability of the wastewater. The improvement of biodegradability is an essential requirement environmentally for pharmaceutical effluents resistant to biological treatment (Lester et al. 2013). However, ozone selectively reacts with some organic matters, and ozone cannot completely decompose the organic matters in low dosages and short timescales. Ozonation must be used in combination with other water treatment technologies to achieve the ideal processing effects. Hydrolysis-acidification refers to the anaerobic process controlled in the anaerobic hydrolysis and acidification stage, in which acid-producing bacteria are used to change the non-dissolved organic mater into dissolved organic matter, to turned hardly biodegradable organic matter into easily biodegradable organic matter and to improve the biodegradability of wastewater.

The aim of the study was to dispose of pharmaceutical tail water with the ozonation–hydrolysis acidification, to improve tail water biodegradability and to improve treatment efficiency.

MATERIALS AND METHODS

Experimental devices

The pilot scale ozonation pond and hydrolysis acidification pond were used as experimental devices. Figure 1 shows a process flow diagram and the running parameters of ozonation pond and hydrolysis-acidification pond are shown in Table 1.
Table 1

Running parameters

Running parameters Ozonation pond Hydrolysis-acidification pond 
Effective volume 1.56 m3 3.0 m3 
Wastewater flow 200 L/h 350 L/h 
Hydraulic retention time 1.3 h 8.6 h 
Running parameters Ozonation pond Hydrolysis-acidification pond 
Effective volume 1.56 m3 3.0 m3 
Wastewater flow 200 L/h 350 L/h 
Hydraulic retention time 1.3 h 8.6 h 
Figure 1

Process flow diagram.

Figure 1

Process flow diagram.

A gas–liquid mixing pump was used to convey pharmaceutical tail water into an ozonation pond equipped with an ozone generator with gas production (15 g/L), and sodium thiosulfate was used to absorb ozone tail gas. The influence and effluence BOD (biochemical oxygen demand), COD (chemical oxygen demand) were measured according to the experimental need.

Tail water quality

After three months monitoring, some pollutants concentrations of pharmaceutical tail water were evaluated, and a 90% guarantee rate was used as an evaluation index of water quality guarantee rate. Evaluated concentrations of different water quality indexes were obtained under a given guarantee rate through statistical analysis of monitoring data, and the evaluated concentration is shown in Table 2.

Table 2

The estimate concentration under different guarantee

The water quality index Guarantee(%) Concentration (mg/L) 
COD 90.9 300 
BOD 97.0 35 
SS 95.0 150 
NH3-N 91.0 30 
The water quality index Guarantee(%) Concentration (mg/L) 
COD 90.9 300 
BOD 97.0 35 
SS 95.0 150 
NH3-N 91.0 30 

In addition, the monitoring results showed that the pH of the pharmaceutical tail wastewater was alkaline, all data of pH were greater than 7, the maximum being 10. The BOD/COD ratio of pharmaceutical wastewater was lower than 0.20, which was difficult to be biodegraded. GC-MS was used to detect specific components of the COD in the tail water. The results measured by GC-MS showed that there were 51 types of organic substances, including alkanes, pyridine, aniline, ketone, ether and other heterocyclic compounds.

Detection method

In the tests, BOD, COD, pH, SS, NH3-N and organic substances were detected and the specific detection methods are shown in Table 3.

Table 3

Detection methods

Detection of the targets Detection methods 
COD Potassium dichromate oxidation method 
BOD Five days biochemistry method 
SS Gravimetric analysis 
NH3-N Nessler's reagent spectrophotometry 
51 types of organic substances Gas chromatography – mass spectrometry combined method 
Detection of the targets Detection methods 
COD Potassium dichromate oxidation method 
BOD Five days biochemistry method 
SS Gravimetric analysis 
NH3-N Nessler's reagent spectrophotometry 
51 types of organic substances Gas chromatography – mass spectrometry combined method 

RESULTS AND DISCUSSION

Determining the adding dosage of ozone

In order to determine the appropriate dosage of ozone, the removal rate of COD and the guarantee rate of COD removal were investigated under conditions of ozone dosage of 2.5, 10, 20 and 30 mg/L. Specific results are shown in Figure 2.
Figure 2

The ozone dosage and COD removal rate curves.

Figure 2

The ozone dosage and COD removal rate curves.

From Figure 2 it can be seen that the COD removal rate fluctuated and the guaranteed rate of COD removal increased along with the ozone dosage, increasing from 2.5 to 30 mg/L. At the ozone dosage of 30 mg/L the removal rate of COD was18.2% and the guaranteed rate reached 65% which shows that the ozone dosage of 30 mg/L is reliable.

Determining the optimal oxidation time

In order to acquire the optimal oxidation time, 30 mg/L of ozone dosage rate was used to investigate the COD removal rate after 30, 45 and 60 minutes. The results from Figure 3 show that the COD removal rate increased slowly from 30 to 60 minutes. When the reaction time is 60 minutes, the COD removal rate can be higher than 25%. In the actual operation process the oxidation time can be determined according to the COD removal rate required.
Figure 3

The ozonation time and COD removal rate charts.

Figure 3

The ozonation time and COD removal rate charts.

Ozonation-hydrolytic acidification treatment of pharmaceutical tail water

The running time of the ozonation-hydrolysis acidification process was 6 days and the BOD and COD of each part of the system were monitored every day. The COD curves are shown in Figure 4. After acidification the COD of the influent organic reduces, and through further ozonation treatment the COD increases. Although a part of the organic matter was degraded by the hydrolysis acidification process, through high efficiency ozonation treatment the large molecules of organic substances were changed into small molecules of organic matter which were easily detected by the COD detection method.
Figure 4

The running time and COD value curves.

Figure 4

The running time and COD value curves.

Figure 5 shows the curve of the COD removal rate for the whole system. With the increase of the runtime of the system, the COD removal rate changes with run time, firstly increasing and then decreasing, and finally increasing. The COD removal rate changes from 20% to 50%.
Figure 5

The running time and the COD removal rate curves.

Figure 5

The running time and the COD removal rate curves.

Figure 6 shows the curves of the B/C (BOD/COD) value. The B/C value of the tail water from pharmaceuticals is generally greater than 0.25, and the biodegradability is improved.
Figure 6

The running time and the B/C curves.

Figure 6

The running time and the B/C curves.

The changes of organic substances types in the process are described in Tables 4 and 5. From the GC-MS test report it can be seen that organic compounds of pharmaceutical wastewater included alkanes, pyridine, aniline, ketones, ethers and other heterocyclic compounds, of which lipids accounted for the highest proportion. After ozonation the proportion of the alkanes elevated and the proportion of the other organic substances decreased. The cause of hydrocarbons alkanes elevating was that some heterocyclic organic substances were turned into hydrocarbons by ozonation. After hydrolysis the proportion of alkanes decreased, which testified that hydrolysis had an obvious effect on the long chain alkane.

Table 4

All types of organic matter ratio

Type Benzene series Aldoketones Alkanes Lipid Other 
Inflow content (%) 5.20 0.63 28.35 55.37 10.45 
After ozonizing content (%) 10.05 0.30 71.36 12.31 5.98 
After hydrolyzing content (%) 10.65 1.34 49.45 23.82 14.74 
Type Benzene series Aldoketones Alkanes Lipid Other 
Inflow content (%) 5.20 0.63 28.35 55.37 10.45 
After ozonizing content (%) 10.05 0.30 71.36 12.31 5.98 
After hydrolyzing content (%) 10.65 1.34 49.45 23.82 14.74 
Table 5

The proportion of the various components of the tailwater

Name of organic matter Inflow (mg/L) Ratio (%) Ozonizing effluent (mg/L) Ratio (%) Hydrolyzing effluent Ratio (%) 
Benzene 0.0132 0.456337 0.1124 1.2906 0.0047 0.26 
Chloroaceton 0.0012 0.041485   0.0188 1.03 
1-Chloro-2-propanol 0.0008 0.027657     
Acetin 0.2379 8.224435   0.0048 0.26 
Methylbenzene and Aalkylbenzene 0.0839 2.900505 0.0244 0.2802 0.034 1.86 
Methyl isobutenyl ketone 0.0024 0.082970     
Diacetone alcohol 0.0117 0.404480 0.0258 0.2963 0.0058 0.32 
4-Hydroxy-2-pentanone 0.0016 0.055314     
1,1,3,3-Tetramethylthiourea 0.005 0.172855 0.0396 0.4547 0.0237 1.29 
Long-chain paraffin 0.8201 28.351656 6.215 71.3646 0.9057 49.45 
2,4-Di-tert-butylphenol 0.0534 1.846090 0.733 8.4168 0.1523 8.32 
PAEs 1.3636 47.140980 1.072 12.3094 0.4314 23.55 
Unknown ketone compounds 0.0013 0.044942     
1,3-Benzodioxole 0.01 0.345710 0.0054 0.0620 0.0071 0.39 
Oleic acid amide 0.0805 2.782963 0.0253 0.2905 0.0319 1.74 
Erucylamide 0.206 7.121621 0.216 2.4802 0.1128 6.16 
Stearic acid   0.0038 0.0436   
Palmitic acid   0.2304 2.6456   
N-Phenyl-1-naphthylamine   0.0057 0.0655 0.004 0.22 
Unknown ethers     0.0878 4.79 
Diaveridine     0.0067 0.37 
Name of organic matter Inflow (mg/L) Ratio (%) Ozonizing effluent (mg/L) Ratio (%) Hydrolyzing effluent Ratio (%) 
Benzene 0.0132 0.456337 0.1124 1.2906 0.0047 0.26 
Chloroaceton 0.0012 0.041485   0.0188 1.03 
1-Chloro-2-propanol 0.0008 0.027657     
Acetin 0.2379 8.224435   0.0048 0.26 
Methylbenzene and Aalkylbenzene 0.0839 2.900505 0.0244 0.2802 0.034 1.86 
Methyl isobutenyl ketone 0.0024 0.082970     
Diacetone alcohol 0.0117 0.404480 0.0258 0.2963 0.0058 0.32 
4-Hydroxy-2-pentanone 0.0016 0.055314     
1,1,3,3-Tetramethylthiourea 0.005 0.172855 0.0396 0.4547 0.0237 1.29 
Long-chain paraffin 0.8201 28.351656 6.215 71.3646 0.9057 49.45 
2,4-Di-tert-butylphenol 0.0534 1.846090 0.733 8.4168 0.1523 8.32 
PAEs 1.3636 47.140980 1.072 12.3094 0.4314 23.55 
Unknown ketone compounds 0.0013 0.044942     
1,3-Benzodioxole 0.01 0.345710 0.0054 0.0620 0.0071 0.39 
Oleic acid amide 0.0805 2.782963 0.0253 0.2905 0.0319 1.74 
Erucylamide 0.206 7.121621 0.216 2.4802 0.1128 6.16 
Stearic acid   0.0038 0.0436   
Palmitic acid   0.2304 2.6456   
N-Phenyl-1-naphthylamine   0.0057 0.0655 0.004 0.22 
Unknown ethers     0.0878 4.79 
Diaveridine     0.0067 0.37 

CONCLUSIONS

  1. The ozone unit test showed that with the ozone dosage increasing from 2.5 to 30 mg/L, the COD removal rate had been gradually improved.

  2. The ozonation-hydrolysis acidification test indicated that COD removal rate of whole system was above 30% under ozone of 25 mg/L. After the ozonation-hydrolysis acidification process the B/C value of the pharmaceutical tail water was greater than 0.25, and biodegradability was enhanced.

  3. The organic compounds in tail water included alkanes, pyridine, aniline, ketones, ethers and other heterocyclic compounds from the GC-MS test report. After hydrolysis the proportion of alkanes decreased, which testified that hydrolysis had an obvious effect on the long chain alkane.

  4. After ozonation-hydrolysis acidification treatment, the pharmaceutical tail water was discharged into an urban sewage plant and mixed with domestic wastewater and the mixed wastewater treated by biological processes could meet national emission standards.

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