Research On Pharmaceutical Wastewater Treatment Technologies And Tracing Refractory Pollutants

Pharmaceutical wastewater was a kind of typical refractory organic wastewater with the characteristics of high concentration of organics and salinity, poor biodegradability and bio-toxicity for some components. With the promotion of energy-saving emission reduction and the rising discharge standards for pharmaceutical wastewater, the treated wastewater with biological treatments as its main process have already failed to meet the discharge standards, as a result, many pharmaceutical companies faced the bottleneck of sustainable development. To settle this problem, besides developing new advanced treatment technologies based on existing biological treatments, tracing refractory components from production processes was also urgent to do. Reducing pollution load especially with the components of toxic and refractory matters from the source using cleaner production processes, and then introducing effective pre-processing techniques to reduce these matters, which can reduce the burden of following-up biological treatment process.In this study, wastewater discharged from a pharmaceutical company in Hangzhou Bay Fine Chemical Park was chosen as an object, the treatment effects and existing problems for field processes were evaluated. At the same time, pilot studies using membrane bioreactor instead of CASS process were conducted in the lab to improve effluent quality. The major sources of refractory materials were identified with the combination technology of traceability analysis and chromatography techniques.The main conclusions are as follows:(1) The treatment process this pharmaceutical company applied was aerobic - hydrolytic acidification-CASS processing, the COD removal rate in the first aerobic biological process was 57%, hydrolytic acidification process performed no significant effect on COD removal and less then 20% COD was removed by second aerobic biological treatment, the average COD concentration in the effluent was 1100 mg/L which can't meet the discharge standard of 800 mg/L. The ammonia nitrogen can't be removed by this hybrid process.(2) In a small scale research with the hybrid process of aerobic - hydrolytic acidification - membrane bio-reactor(MBR), the average COD concentration in influent was 4500-7000 mg/L, the COD concentration in the treated water was less then 1000mg/L with the removal rate of 85%. The COD removal rate in first aerobic process, hydrolytic acidification and MBR process was respectively 55%, 10% and 20%. More than 90% of ammonia nitrogen and 70% of total nitrogen were removed by this hybrid process.(3) The biodegradability evaluation method for wastewater was established and then tracing refractory pollutants from each production section by using this method. After evaluating dozens of production sections from ten workshops, refractory pollutants were screened from seven production sections from two workshops, there were W1-1,W1-3,W1-5,W1-6,W2-1,W2-3and W2-7. The amount of refractory pollutants discharged from above seven production sections accounted for above 95% of total refractory pollutants from ten workshops. The above results were basically in consistent with the results obtained from Wabo's breath test.(4) The wastewater from section W1-3 contained pyridine and its bio-toxicity was far higher than other sections. Its bio-toxicity was not significantly decreased after shaking flask biodegradation test. However, the bio-toxicity of wastewater discharged from section W1-1 and W1-6 were enhanced, indicating that the photobacterium bio-toxicity from biodegradation intermediates was higher than that of parent material.(5) The result of GC/MS and GC/ECD analysis indicated that 32 organics were detected in the company's wastewater, 21 organics were detected in the effluent of hybrid process, 12 of which were also detected in the company's wastewater and the rest 9 organics were new synthetic materials. The residue materials in the treated wastewater were heterocyclic aromatics, heterocyclic substances with nitrogen and sulfur and multi-ring material, all of which were hard to be removed by biological process and became the bottleneck of advanced treatment. In addition, high concentration of dichloromethane, chloroform and cyclohexanone were detected sometimes in the raw wastewater and treated wastewater, indicating that halogenated hydrocarbon solvent were largely used in raw materials or the recovery was very low. Dichloromethane with a high content may had side effect on anaerobic bacteria and lead to the hydrolysis acidification process failed.