Pilot Scale Biological Treatment as Pre-Treatment for Reverse Osmosis

Treatment of pharmaceutical wastewaters is a challenging task owing to their complexity and pollution load, variability in strength of waste streams accompanied with shock loads. Since no single treatment system is a viable option, integration of existing systems with advanced physical/chemical processes has been gaining attention for treatment of pharmaceutical wastewater. In the present study, two biological treatment methods were evaluated for their efficiency as pre-treatment system for RO which are sequencing batch reactor and membrane bioreactor. Efficiency of biological treatments tested SBR and MBR was presented in terms of percentage removal of physico-chemical parameters. Total dissolved solids removal by SBR was 31.82% while MBR showed 29.25% reduction. Chemical oxygen demand removal by SBR was 69.54% while MBR showed 30.35% removal. Efficiency of combined treatments SBR-RO and MBR-RO was presented in terms of removal of total dissolved solids, COD and ammonia. TDS removal was the highest in the combination of SBR-RO with 95.94% removal, while MBR-RO combination resulted in 87.29% removal. Chemical oxygen demand was achieved maximum with the combination of MBR-RO 92.33% while competitive results were achieved with the combination SBR-RO also with 88.62% removal. Removal of ammonia was maximum with the combination SBR-RO 87.5%, while competitive results were obtained with MBR-RO 85.51%. From the results, it can be understood that SBR was efficient in removing ammonia, total dissolved solids and was equally competent in removing chemical oxygen demand. This study concludes that combined treatment of SBR-RO proves to be promising in treating pharmaceutical wastewaters.


Introduction
Treatment of pharmaceutical wastewaters is a challenging task owing to their complexity and pollution load, variability in strength of waste streams with shock loads. These factors govern the effectiveness of conventional treatment systems. Since no single treatment system is a viable option, integration of existing systems with advanced physical/chemical processes has been gaining attention for treatment of pharmaceutical wastewater.
Simplicity in process and single tank design of SBR coupled with flexible technology has been recognized as a desirable treatment option for different types of wastewater [1]- [6]. Unique characteristics of SBR include its competence in removal both organic matter and nitrogen from wastewater [7] [8] [9]. Conditions of both aerobic and anaerobic can be adopted in SBR for removal of phosphorus [10] [11] [12]. These properties of SBR make it viable economically [13].
SBR applied for treatment of olive mill wastewaters showed significant removal of pollution load through 60% removal of total polyphenols and 90% removal of chemical oxygen demand respectively [14]. When used to treat swine wastewater the reactor presented excellent purification of wastewaters. Removal of total phosphorus, total nitrogen ammonia-nitrogen and COD were in the order of 96.2%, 95.6%, 95.7%, and 98.2% respectively [15]. SBR treatment was also adopted for pharmaceutical wastewaters, though less work has been reported the results were promising. Study of wastewater containing antibiotic was carried out by Elmolla and Chaudhuri, 2011 [16].
Modern hybrid wastewater treatment adopting membrane separation technology along with biological process is Membrane bio-reactor (MBR) [17]. Utilized as biochemical engineering processes, MBR can be used as suspended growth bioreactor functioning processes like bio-oxidation, fermentation, nitrification and denitrification along with separation of solid and liquid [18]. Further, this can also be operated at high sludge concentrations [19]. MBRs are well appreciated for their efficiency in removing dissolved solids [20] [21]. Major concern of MBR system is fouling of membrane which indicates accumulation of rejected constituents on the membrane resulting in resistance to water transport through the membrane [22]. Greater than 80% removal efficiency for pharmaceuticals was reported by Radjenovic et al., 2007 [23].
Membrane technologies have gained significant importance in treating wide array of industrial wastewaters during the past decades. Among others, reverse osmosis (RO) has been specifically appreciated as state of art in treatment of wastewater. RO has been adopted for treating industrial wastewaters from petrochemical, chemical, pulp and paper, food industries, electrochemical, municipal wastewater, textile and also for treatment of drinking water [24] [25] [26].
Permeate from this process has high quality with potential to reuse for various processes like dyeing, boilers cooling-towers and cleaning, etc.
However, application of RO faces major hurdle with reference to membrane fouling which impacts efficiency of treatment both qualitatively and quantita-Journal of Water Resource and Protection tively, increasing operation costs due to resistance in filtration, production of corrosive by-products and passage of salts [27] [28]. Owing to fouling reason extensive pre-treatment is required for successful functioning of these systems [29] [30]. Comparative study between conventional biological treatment and MBR as pre-treatment options for RO was studied and revealed that MBR was more suitable [31]. Current research focusses on testing the efficiency of biological treatments SBR and MBR as viable pre-treatment options for RO.

Process
Biological treatment using sequencing batch reactor and membrane bioreactor was studied. Efficiency of the process was evaluated in terms of reduction in total dissolved solids and chemical oxygen demand. Treated waters from each of the unit are fed to reverse osmosis for a duration of one month to evaluate their efficiency as pre-treatment to reverse osmosis ( Figure 1).

Sampling Site and Sample Collection
All the samples were collected from the treatment plant of the pharmaceutical industry. Water samples from sequencing batch reactor and membrane bioreactor were collected once every day. Samples from sequencing batch reactor were collected from feed and outlet respectively and for membrane bioreactor and reverse osmosis samples from feed, permeate and reject were collected.

Analytical Procedures
The following parameters for the collected samples were analysed pH, total dissolved solids and chemical oxygen demand. All parameters were analysed as per the standard methods of APHA, 2015 (Table 1).

Results
This research presents the results from pilot scale studies focussed on to study the most suitable pre-treatment for reverse osmosis (RO) treatment. Sequencing batch reactor (SBR) and Membrane bioreactor (MBR) were assessed for their suitability as pre-treatment options to RO. Table 2 illustrates one month (June, 2016) data of SBR tested for its suitability  as preliminary treatment for Reverse Osmosis process. One month data on a daily basis was presented. Efficiency of the process was tested with reduction in parameters total dissolved solids and chemical oxygen demand. Further as surrogate for removal of TDS and COD, sludge volume and dissolved oxygen respectively were also recorded. The highest and lowest TDS reduction was rec-  Percentage reduction of ammonia with maximum and minimum was 87.50% and 78.00% respectively ( Figure 2).    Table 4 presents the biological treatment of pharmaceutical wastewaters using membrane bioreactor (MBR) on pilot trail during the month of August 2016. Efficiency of the treatment is defined in terms of reduction in strength of wastewaters with parameters of total dissolved solids, total solids, chemical oxygen demand and turbidity. The percentage removal of the parameters under test, as understood from the permeate values the TDS removal was recorded to be 1.38% as the lowest and 29.25% as the highest. While TSS has showed 100% removal, the COD removal varied from 4.77% to 30.35%. Turbidity removal was good with 80.90% being the lowest and 99.86% recorded as the highest (Figure 3).  4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 Efficiency of Reverse Osmosis with SBR as pre-treatment TDS COD Ammonia   While hardness showed 93.33% -100% removal, ammonia removal was good with 71.46% being the lowest and 85.51% recorded as the highest (Figure 4). Table 6 illustrates the comparison of total dissolved solids and chemical oxygen demand removal by sequencing batch reactor and membrane bioreactor.
Comparison of treatment efficiency of reverse osmosis with SBR and MBR as pre-treatment in terms of TDS, COD and Ammonia removal is presented in Table   7. Total dissolved solids removal was the highest in the combination of SBR-RO

Discussion
The prime objective of the current research is to evaluate the efficiency of sequencing batch reactor (SBR) and membrane bioreactor (MBR) as pre-treatment for reverse osmosis (RO).   [41]. An increase in dissolved oxygen is observed when all the organic matter is degraded, reducing the respiration of microbes.  Sequencing batch reactor as pre-treatment to Reverse Osmosis

Sequencing Batch Reactor
One-month trail runs were performed wherein treated effluent from SBR is fed to reverse osmosis. The results were promising with the higher end removal of TDS, COD and ammonia recorded as 96%, 88.62% and 87.50% respectively.
Meagre studies are found in context of integrated treatment using SBR followed by RO especially for treating pharmaceutical wastewaters. Gangavarapu et al., 2015 [42] conducted a study on medium scale active pharmaceutical ingredient manufacturing industry that adopted recycling process through zero liquid discharge system. They reported the flow of effluent treatment process consisted of multi-effect evaporator followed by sequencing batch reactor which is concluded by reverse osmosis. They achieved reduction in total dissolved solids, total suspended solids and biological oxygen demand in the order of 99.2, 100 and 100 percent respectively. A combination of membrane sequencing batch reactor with reverse osmosis has achieved 90.9% reduction in chemical oxygen demand, 92% of total organic carbon and 91.5% of oil and grease from produced water of oil and gas field [43].

Membrane Bioreactor
MBR processes are experiencing exceptional growth in treating domestic and municipal wastewater during the past decade owing to many advantages like exceptional quality of effluent, lesser production of sludge, lower foot print and flexibility for expansion in future [44]. Industrial use of MBR technology gained attention attributed to the robustness in its process, resistance to high organic loading, ability to treat compounds that are difficult and inhibiting to treat [45].
Pharmaceutical wastewaters manufacturing vitamins were conventionally treated using two units of oxidation process wherein the treated water was unstable with greater amounts of suspended solids among other pollution parameters. Hence Almost all the studies focus on removal of TSS but not TDS. Moreover, TDS removal is always reported when MBR is used as a pre-treatment for RO. Hence, in the present study also the removal of TDS will be dealt in the following section of MBR as pre-treatment for RO.

 Removal of Total Suspended Solids
In the present study, TSS concentrations in permeate were recorded to be zero

Comparison of Sequencing Batch Reactor and Membrane Bioreactor
In the present study maximum reduction of total dissolved solids was obtained  From the results and discussion, it can be understood that individually SBR was effective over MBR. Though as pre-treatment the combination of MBR-RO was a little high, SBR-RO was equally competent. Since, reverse osmosis is efficient in removing solids, removal of chemical oxygen demand and ammonia in biological treatment is more desirable to get an overall effective treatment.

Comparison between SBR and MBR as Pre-Treatment for RO
Hence, the combination of SBR-RO was tested on a full scale in the further studies.

Conclusions
Removal of chemical oxygen demand from wastewaters requires adopting biological treatment. Available conventional biological treatments are not able to treat to the required standards. Literature review stated the use of hybrid processes or combination of various treatment technologies to achieve discharge standards. Hence, in the present study a combination of advanced biological process and advanced physical membrane separation process were chosen to test their combined efficiency in treating pharmaceutical wastewaters. The biological treatment methods evaluated for their efficiency are sequencing batch reactor and membrane bioreactor, further their suitability as pre-treatment to reverse osmosis treatment was also evaluated. Efficiency comparison among biological treatments SBR and MBR: Total dissolved solids removal by SBR was 31.82% and MBR showed 29.25%. SBR even though presented the highest removal was quite fluctuating in treatment process. Chemical oxygen demand removal by SBR was 69.54% and MBR showed 30.35% removal of COD. Since the prime objective of biological treatment is removal of chemical oxygen demand and SBR was efficient over MBR, SBR was selected for biological treatment of pharmaceutical wastewaters.
Efficiency comparison among combined treatments of SBR-RO and MBR-RO: Removal of total dissolved solids was the highest in the combination of SBR-RO treatment with 95.94% removal. While MBR-RO combination resulted in 87.29% removal. Chemical oxygen demand was achieved maximum with the combination of MBR-RO 92.33% while competitive results were achieved with the combination SBR-RO also with 88.62% removal. Removal of ammonia was maximum with the combination SBR-RO 87.5%, while competitive results were obtained with MBR-RO 85.51%. From the results, it can be understood that SBR was efficient in removing ammonia and total dissolved solids and was equally competent in removing chemical oxygen demand. Since, reverse osmosis is efficient in removing solids, in biological treatment removal of chemical oxygen demand and ammonia are more desirable to get an overall effective treatment. Hence, the combination of SBR-RO was tested on a full scale in the further studies.

Conflicts of Interest
The authors declare no conflicts of interest regarding the publication of this paper.