Biological Removal Of Pharmaceuticals Physicochemical Characterisation Of Influent Biology Essay

Published:

This essay has been submitted by a student. This is not an example of the work written by our professional essay writers.

The inflow of the wastewater was monitored during the period between September 2010 and August 2011. These data showed that the inflow of the wastewater ranged between 271000 and 298400 m3/day. The physico-chemical parameters of the influent during the sampling period exhibit large variations. The wastewater temperature values varied from 23 °C at winter and 35 °C at summer. The pH values varied from 7.0 to 7.2 and the values of nitrogen, phosphorous, chemical oxygen demand (COD), EC and suspended solids (SS) fluctuate during the sample year (see appendix).

Performance of wastewater treatment processes of Sulaibiya

The physico-chemical properties of the effluent are presented in appendix. The total phosphorus content and the total Kjeldahl nitrogen content decreased from 6.3 mg/L to 1.6 mg/L and 43.5 to 2.5 mg/L, respectively.

Phosphorus and nitrogen are normally known as limiting nutrients for eutrophication in natural balance of aquatic ecosystems. Therefore, careful manage of their discharge is important to prevent excessive algal growth (Andersen et al., 2006). The primary and secondary treatments of the wastewater effectively reduced the phosphorus and nitrogen by 75 and 94%, respectively. Significantly the effluent had a better quality in regards to the nitrogen and organic contents due to the efficiency of the activated sludge process in the WWTP where average COD removals were 93%. The suspended solids in the secondary effluent are much lower than the influent by 95%. During the primary and secondary treatments, the cations concentrations did not change significantly which can be seen by the only small change in the electrical conductivity between the influent and effluent with average reduction of 17% where other researcher's results (7%) as reported by Tchobanoglous et al. (2007).

Occurrence of pharmaceuticals in wastewater influents

The concentrations of the target pharmaceuticals in the influent over the year long sampling period at Sulaibiya are summarized in (Figures). Trimethoprim, sulphamethoxazole, paracetamol and ranitidine were found in all influent samples whereas, metronidazole were not detected in October and November. Metronidazole detection was ranging between 4ng/l at December and 58ng/l at April lower than other reported (Rosal et al., 2010). Trimethoprim and sulphamethoxazole were found in the influent in the range of 61-1814 and 11-1669, respectively. The highest concentration of trimethoprim was found at August and the lowest was found at April whereas the highest concentration of sulphamethoxazole was found at October and the lowest was at February.

Trimethoprim was reported at 290 ng/L in raw influent water in Switzerland (Goebel et al., 2005) and at relatively high concentrations from2100-7900 ng/L in the US (Batt et al., 2007). On the other hand, sulphamethoxazole was reported at high concentration was 6000ng/l (Batt et al., 2005) and at lower concentration was 70ng/l which was higher than our results. Paracetamol and ranitidine was found in the influent at concentrations significantly higher than other target drugs which were the top ten pharmaceuticals dispensed in Kuwait. Paracetamol was detected in all of the wastewater samples at concentrations ranging from 101-2086 ng/L with the highest concentrations in November 2010 and lowest concentrations in February 2011. These concentrations were to some extent lower than those reported previously (Pham and Proulx, 1997; Ternes 1998; Blanchard et al., 2004). On the other hand, ranitidine was ranging from 365 to 2009 ng/L. These concentrations are consistent with other studies with concentrations of lower detection up to 580 ng/L (Kolpin et al., 2002) and higher detection at 1700 ng/l (Gomez et al., 2006).

According to the fluctuated temperature during the sampling between summer and winter. This fact might indicate that the concentrations of pharmaceuticals in the influent may be related to higher consumption during the cold periods of the year when more illness occurs.

Figure 5-9: Variation of concentration of various target compounds (ng/L) in the

influent- each circle in line represents one sample

Figure: Concentrations of pharmaceuticals (ng/L) in the influent and the removal percentage by the secondary treatment processes of Sulaibiya.

Removal of pharmaceuticals during the primary and secondary treatment in Sulaibiya

The removal rates of pharmaceuticals during the sampling period were shown in Figure. Paracetamol was removed efficiently by the secondary treatment, at an average 97.5% with highest removal reached 99.9% and lowest removal was 86.1%. Trimethoprim was removed lower than paracetamol with average removal 86.1% where the highest removal was 96.1% and the lowest removal was 63%. Removal efficiency of metronidazole in secondary treatment was at average 83.4% with highest removal was 93.9% and lowest removal was 59.4%. Sulphamethoxazole and ranitidine were the lowest removal efficiency with average 77.5% where the highest removal of sulphamethoxazole was 98.7% and lowest removal was 31.3% while the highest removal of ranitidine was 99.2% and lowest removal was 47.4%.

In general, the removal efficiencies found in this study were consistent with other WWTP using primary and secondary treatment with activated sludge. For example, 75% removal rate in German (Ternes, 1998; Stumpf et al., 1999), up to 90% in Spain (Santos et al., 2007) and up to 99% in Japan (Nakada et al., 2006) were reported. These removal rates for a single compound can vary greatly from one WWTP to another depending on the type of treatment (e.g. biological and physico-chemical) and the residence time of water in the primary sedimentation tank (Santos et al., 2007).

Removal efficiency of metronidazole has been reported with a large variability range from 65-80% in Spain (Gros et al., 2010). On the other hand trimethoprim was reported incomplete removal during conventional treatment by several studies ( Gobel et al., 2007; Jelic et al., 2011) while Gros et al.,2010 report 65 to 80% removal efficiency in the plants with higher hydraulic retention times. Similar observation for the removal efficiency of sulphamethoxazole and ranitidine were found by other researcher where they report removal efficiency 30-92% and 50-98%, respectively (Gros et al., 2010). In Germany paracetamol was found to be removed efficiently at 95 % due to its biodegradability and was detected in less than 10% of all sewage effluents (Ternes, 1998; Kolpin et al., 2004; Roberts and Thomas, 2006).

Concentrations of the target pharmaceuticals detected in the WWTP effluent in a range of 1-1000ng/L are presented in Figure. This is in agreement with Ternes et al (1998), who reported that many pharmaceuticals were detected in the effluents and measured at high concentrations due to incomplete removal in German sewage treatment plants.

The efficiency of modern wastewater treatments has increased the removal of pharmaceuticals from influent with the introduction of the activated sludge process. Elimination of pharmaceuticals in the activated sludge process occurs due to several reasons adsorption, biological or chemical degradation and biotransformation. Ternes (1998) suggested that activated sludge removes high amounts of pharmaceuticals than other treatment, most likely to the bacterial activity in the activated sludge. The results of this study showed there was not complete elimination of trace pharmaceuticals in the effluent. Therefore implementing other technologies such as membrane systems would be necessary for complete removal of these traces.

Effect of temperature on the removal efficiency

Although the total concentrations of target compounds in the influent samples through-out the yearly sampling fluctuated , the removal process in the wastewater treatment plant worked as efficiently during the summer months as during the winter months . Therefore, effect of temperature was statically analysed using ANOVA. The correlation between the temperature and the removal of COD, BOD, organic nitrogen, TKN, MLVSS, and target pharmaceuticals was highly significant (table). This conclusion contradicts other researchers who found that the removal processes in wastewater treatment plants was higher in summer than in winter (Vieno et al., 2005). They suggested that the reason was the lower biodegradation in the plant because of low temperature in winter.

Variables

Factor

p-value

Confidence level

Level of Significance

COD removal

Temp

0

100

Highly Significant

BOD removal

Temp

0

100

Highly Significant

Organic nitrogen removal

Temp

0

100

Highly Significant

TKN removal

Temp

0

100

Highly Significant

MLVSS

Temp

0

100

Highly Significant

Metronidazole removal

Temp

0

100

Highly Significant

Trimethoprim removal

Temp

0

100

Highly Significant

Sulphamethoxazole removal

Temp

0

100

Highly Significant

Paracetamol removal

Temp

0

100

Highly Significant

Ranitidine removal

Temp

0

100

Highly Significant

Effect of pharmaceuticals concentration on the removal efficiency

The effect of pharmaceuticals concentration was highly significant on most responses except sulphamethoxazole which was significant effect on COD, BOD, organic nitrogen, and TKN removal, while was highly significant on MLVSS and sulphamethoxazole removal efficiency. This highly significant effect of most target pharmaceuticals on the removal COD, BOD, organic nitrogen, TKN, drug, and MLVSS agrees with the previous qualitative analysis discussed earlier (Sections ), since the removal efficiency and biomass concentrations and characteristics were mainly affected by the dominant factor which was the pharmaceuticals concentration. This highly significant effect on removal efficiencies need to be carefully addressed.

Variables

Factor Concentration

p-value

Confidence level

Level of Significance

COD removal

Metronidazole

0

100

Highly Significant

Trimethoprim

0.002

99.8

Highly Significant

Sulphamethoxazole

0.06

94

Significant

Paracetamol

0.001

99.9

Highly Significant

Ranitidine

0

100

Highly Significant

BOD removal

Metronidazole

0

100

Highly Significant

Trimethoprim

0.003

99.7

Highly Significant

Sulphamethoxazole

0.064

93.6

Significant

Paracetamol

0.001

99.9

Highly Significant

Ranitidine

0

100

Highly Significant

Organic nitrogen

removal

Metronidazole

0

100

Highly Significant

Trimethoprim

0.002

99.8

Highly Significant

Sulphamethoxazole

0.053

94.7

Significant

Paracetamol

0.001

99.9

Highly Significant

Ranitidine

0

100

Highly Significant

TKN removal

Metronidazole

0

100

Highly Significant

Trimethoprim

0.003

99.7

Highly Significant

Sulphamethoxazole

0.063

93.7

Significant

Paracetamol

0.001

99.9

Highly Significant

Ranitidine

0

100

Highly Significant

MLVSS

Metronidazole

0

100

Highly Significant

Trimethoprim

0

100

Highly Significant

Sulphamethoxazole

0

100

Highly Significant

Paracetamol

0

100

Highly Significant

Ranitidine

0

100

Highly Significant

Drug removal

Metronidazole

0

100

Highly Significant

Trimethoprim

0.002

99.8

Highly Significant

Sulphamethoxazole

0.05

95

Highly Significant

Paracetamol

0.001

99.9

Highly Significant

Ranitidine

0

100

Highly Significant

The primary and secondary wastewater treatment gave moderate to high removal efficiencies of pharmaceuticals. However, the effluent still had considerable concentrations of some of these drugs. These concentrations were in the range of 1-1000 ng/L, as most of the pharmaceuticals present in the influent were found in the effluent, which indicate the need for further treatments to remove these pollutants compounds.

In this section, an investigation was made to compare the level of pharmaceuticals concentration between the influent and effluent of a wastewater treatment plant as well as the determination of removal efficiency by the wastewater treatment processes.

In the next section, the mass balance of reverse osmosis and the removal of micropollutants by advance technologies of water recycling processes of LPWRP will be described.

Physical removal of pharmaceuticals during the WWTP

Physicochemical Characteristics

The physicochemical characteristics of the feed and permeate for the ultra filtration process during the sampling year are presented in Appendix. The average value of the physicochemical characteristics of the inlet of ultra filtration was pH (7.04), TSS (8.68mg/l), TDS (437.1mg/l), COD (24mg/l), BOD (4.07mg/l), total iron (1.38mg/l), and total coliforms (426261.2 colonies/100ml).

The average removal efficiencies of the ultra filtration process were 98%, 95% and 99% for the TSS, total iron and total coliforms measurements, while there were no significant changes in the TDS measurements. The concentrations of COD were measured for ultra filtration feed and permeate. Results did not show high removal of trace organic contaminants through the filtration processes where the average removal of COD was 42% while the BOD was 72%. Thus, the ultra filtration process provides an essential pre-treatment for the RO by removing particulate and colloidal material from the feed but the removal is limited to particles larger than the membrane pore size (Van der Bruggen et al., 2003a).

The average removal efficiencies of the RO process for the TSS and total coliforms measurements were 68% and 99%, while there were highly significant removal in the TDS measurements with average removal 96%. Furthermore, the concentrations measurements of BOD for RO feed and permeate show high removal of trace organic contaminants through the filtration processes with average removal 90%.

Trace Organic Compounds may be completely or partially degraded in wastewater treatment a plant that takes place mostly in the activated biological sludge process. Pharmaceuticals fluctuate in their degradation in various wastewater treatment processes. The remaining pharmaceuticals are passed into the ultra filtration then to RO systems.

Pharmaceutical compounds were detected in the RO feed that was derived from the WWTP. These variations were formerly a result of annual fluctuations of compounds in raw wastewater in addition to other processes involved in wastewater treatment.

Most of pharmaceuticals, namely metronidazole, Trimethoprim, sulphamethoxazole, paracetamol, and ranitidine were found in all sample from RO inlets during the sampling year. The average concentrations of these compounds found in the RO inlets were 4ng/l, 61ng/l, 47ng/l, 8ng/l, and 210ng/l for metronidazole, trimethoprim, sulphamethoxazole, paracetamol, ranitidine respectively (Figures). The highest removal efficiency of these compounds was 97% for ranitidine then 92% for sulphamethoxazole and paracetamol as for Trimethoprim was 86%. Lastly the lowest removal efficiency between these compounds was 56% for metronidazole due to low concentration found in RO inlets.

The solubility of these pharmaceuticals varies; some are moderately soluble such as sulphamethoxazole and Trimethoprim where the solubility was 281mg/l, 400 mg/L, respectively; some are highly soluble like ranitidine, paracetamol and metronidazole where the solubility were 24.7g/l, 14g/l and 10g/l, respectively. Log Kow values of these pharmaceuticals ranged between -0.02 and 0.92. The plot of log Kow versus removal efficiency showed a weak positive (Figure). On the other hand, the solubility and log Kow did not correlate with the behaviour of these pharmaceuticals in the RO. According to Tolls (2001) found that log Kow may not be good indicator of the behaviour of pharmaceuticals in the environment. It has been reported that the removal efficiency of solute by ultra filtration and RO is affected by a different parameters such as pH, solute charge, molecular weight and geometry, polarity and hydrophobicity, as well as the membrane surface charge (Van der Bruggen et al., 1998; Van der Bruggen et al., 1999; Kiso et al., 2000; Kiso et al., 2001; Ozaki and Li, 2002; Kimura et al., 2003b; Kimura et al., 2004).

Investigations have been done by previous studies on the removal efficiency of RO compared to other types of membranes and low pressure reverse osmosis where they found a great advantage of using RO in producing a high quality of recycled water. According to Lopez-Ramirez et al., (2006) who found that the reclaimed wastewater for were widely exceed the RO membrane the drinking water standards by. However, the removals results of the RO membrane represent highly reduced pollutants in permeate. Furthermore, micro-organisms were removed from the RO permeate, which would allow safe reuse of water.

Effect of temperature and pH on the removal efficiency

Similarly to biological treatment the temperature was affecting the removal processes in the RO system. The concentrations of target pharmaceuticals in the RO inlets samples during the sampling year was fluctuated during the summer and winter months. Therefore, effect of temperature and pH was also statically analysed using ANOVA. The correlation between the temperature and pH with the removal of BOD, TSS, TDS, total coliforms and target pharmaceuticals was highly significant (table).

In this study, there was no relationship between the removal of pharmaceuticals and the other removal parameter tested such TSS, TDS, BOD, and total coliforms distributed in the RO streams. The regression analysis shows no correlation between the removal efficiency of pharmaceuticals and TSS, TDS, BOD, and total coliforms. This might be due to the complexity of RO feed in treatment plants and to a broad range of rejection. Therefore, it's very difficult to associate these operating parameters with these removal rates.

Although to the wide range of variability and limitation of data, there was no possible to determine the relationship between the removal and molecular weight or molecular size. According to Kimura et al., (2003b) there was a linear relationship between molecular weight of the non-charged compounds and removal. However, in this study, the relationship between the molecular weight and the removal of metronidazole, trimethoprim and ranitidine was observed a linear regression while sulphamethoxazole and was not on the regression line. The physico-chemical characteristics of tested drugs in this study differ from each other. Thus, a relationship between any of these removals could be described by different physico-chemical characteristics such the charge, shape of compounds. Positive correlation between hydrophobicity of non-phenolic compounds (log Kow) and their rejection by nanofiltration was reported by Kiso et al., 2000.

The rejection of nonylphenol and bisphenol A varied greatly especially for NP. Rejection varied between 0 to 100% for nonylphenol and 53% to 100% for bisphenol A (see Figure 6-20).

Rejection mechanisms by RO were investigated by many researchers (Ozaki and Li, 2002; Van der Bruggen et al., 2003b). Rejections may be influenced by dipole moment of compounds, hydrophobicity of compounds represented by Kow and molecular size. As reported by Ozaki and Li (2002), it is difficult and complicated to elucidate the core mechanisms for the rejection of trace organic compounds by RO under actual conditions.

However, most studies on rejection mechanisms by RO were conducted on pilot scales using virgin membranes, high concentrations and using either base or synthetic water. These pilot scales were run under ideal conditions. Snyder and co-workers (2007) suggested that the compounds which breached RO under the full scale were not consistent, and no clear relationship between molecular structure and membrane could be established. Breaching of the RO could be the result of diffusion into and through the membrane, short-circuiting of the membrane or supporting media failure.

6.8 Product water

The concentrations of PhACs and EDCs were reduced as these compounds passed through the dual membrane systems in the water recycling plant. Clofibric acid, diclofenac and phenytoin were not detected in any product water samples. Other compounds (nonylphenol, gemfibrozil, ibuprofen, ketoprofen, naproxen, acetaminophen, primidone, salicylic acid and carbamazepine) were detected in most product water samples with a maximum concentration of 120 ng/L (Table 6-6). Bisphenol A (BPA) was detected in all product water samples with concentrations ranging from 20-464 ng/L. These concentrations are not surprising since BPA had the second highest concentration among the compounds found in the influent. The presence of BPA in the water product would be considered to have a potential impact on the environment and the final user pathway. Recent studies (Nakada et al., 2006; Roberts and Thomas, 2006; Gomez et al., 2007; Santos et al., 2007) have shown that levels of compounds found in the effluent of WWTP are often higher by more than one order of magnitude than the results obtained in this study.

Therefore, it is most likely that the removal of PhACs and other compounds is more effective in the advanced treatment plant using RO systems than other conventional treatment plants (Snyder et al., 2007). Recently, Snyder et al. (2007) have investigated the removal of a broad range of EDCs during drinking and wastewater treatment processes at bench, pilot and full scale. They found that RO membranes removed nearly all investigated compounds to levels less than method reporting limits (MDL) (1-10 ng/L). However, trace levels of some contaminants were still detectable (<MDL) in RO permeate (e.g., gemfibrozil and naproxen). It should be noted that the latter study was a snapshot and it does not give such a comprehensive picture as the work presented here.

Chlorination effect on the pharmaceuticals during the treatment

The effluents of the RO were treated further by chlorine before discharge. Most of pharmaceuticals escape from the RO system and the trace were detected in the RO effluent. The maximum concentration detected was 19ng/l and 15ng/l for Trimethoprim and ranitidine where the other pharmaceuticals were detected at 7ng/l, 5ng/l, and 4ng/l respectively. On the other hand, the lowest concentration detected in the RO effluents for metronidazole, trimethoprim, sulphamethoxazole, paracetamol, and ranitidine were 0.2ng/l, 1ng/l, 0.2ng/l, 1ng/l, and 1ng/l respectively.

The occurrence of pharmaceuticals in the environment, mainly in water, is a topic that has attracted a strong attention since the last 10 years. In this time, several therapeutic classes of drugs and their human and animal metabolites have been found in the aqueous environment at levels reaching several mg/L in wastewater (Petrovic and Barcelo, 2007; Reemtsma and Jekel, 2006). The incomplete removal of these pollutants at wastewater treatment plants (WWTPs), not designed for this task, has permitted their spread through surface waters (Boyd et al., 2003; Carballa et al., 2004; Kim et al., 2007; Metcalfe et al.,

2003; Okuda et al., 2008; Pa´xeus, 2004; Reemtsma et al., 2006; Tauxe-Wuersch et al., 2005; Ternes, 1998), which is actually a primary source of drinking water. Subsequently, some pharmaceuticals are again not completely removed during drinking water production and thus, they have been identified in drinkable water at the ng/L level (Drewes et al., 2002; Kim et al., 2007; Mompelat et al., 2009; Stackelberg et al., 2004, 2007; Ternes et al., 2002).

Paracetamol is easily degraded by deacetylation to para-aminophenol

P-aminophenol is an analog and metabolite of common household analgesics, such as acetaminophen. It is well-known that acetaminophen in overdose can cause severe hepatic centrilobular necrosis in humans and experimental animals (Thomas, 1993 and Boyd and Bereczky, 1966). Like acetaminophen, p-aminophenol-induced hepatotoxicity may also involve a chemically reactive intermediate and GSH may play an important role in its toxicity. This possibility has not yet been explored (Klos et al. ,1992).

P-aminophenol is a nephrotoxic metabolite of acetaminophen. It is 5 times more potent than acetaminophen as nephrotoxicant in F344 rats. Inhibition of acetaminophen deacetylation to p-aminophenol diminished renal toxicity, suggesting that acetaminophen renal toxicity is partly mediated by formation of p-aminophenol.

P-aminophenol nephrotoxicity is site-specific for the S3 segment of the proximal tubule (Harmon, 2006).

Molecular weight 171.2a

Log Kow-0.02 at 25°Ca

Water solubility 10 g/L at 25°Cb

------------------------------------------------------------

log Kow = 0.91

290.32

Solubility in water: 400 mg/l @ 25 deg. C.

Log Kow sulphamethoxazole

Molecular Weight (g/mol) 253.28

Water Solubility (mg/L) 281

Log Kow 0.92

Molecular Weight

151.16

Corrosivity

Disassociation

pKa = 9.38

log P (octanol-water)

log Kow = 0.46

Solubilities

Very slightly sol in cold water, considerably more sol in hot water; sol in methanol, ethanol, dimethylformamide, ethylene dichloride, acetone, ethyl acetate; slightly sol in ether; practically insol in petroleum ether, pentane, benzene.

In water, 14 g/L at 25 deg C

Kow 0.27

Molecular weight: 350.9

Water Solubility 

24.7 g/L

Writing Services

Essay Writing
Service

Find out how the very best essay writing service can help you accomplish more and achieve higher marks today.

Assignment Writing Service

From complicated assignments to tricky tasks, our experts can tackle virtually any question thrown at them.

Dissertation Writing Service

A dissertation (also known as a thesis or research project) is probably the most important piece of work for any student! From full dissertations to individual chapters, we’re on hand to support you.

Coursework Writing Service

Our expert qualified writers can help you get your coursework right first time, every time.

Dissertation Proposal Service

The first step to completing a dissertation is to create a proposal that talks about what you wish to do. Our experts can design suitable methodologies - perfect to help you get started with a dissertation.

Report Writing
Service

Reports for any audience. Perfectly structured, professionally written, and tailored to suit your exact requirements.

Essay Skeleton Answer Service

If you’re just looking for some help to get started on an essay, our outline service provides you with a perfect essay plan.

Marking & Proofreading Service

Not sure if your work is hitting the mark? Struggling to get feedback from your lecturer? Our premium marking service was created just for you - get the feedback you deserve now.

Exam Revision
Service

Exams can be one of the most stressful experiences you’ll ever have! Revision is key, and we’re here to help. With custom created revision notes and exam answers, you’ll never feel underprepared again.