The respective abbreviations of the pharmaceuticals represent the following pharmaceuticals: paracetamol (Para), salicylic acid (Sali), chlorpheniramine maleate (Chloro), diclofenac (Diclo). The respective abbreviations of the pharmaceuticals represent the following pharmaceuticals: paracetamol (Para), chlorpheniramine maleate (Chloro), stavudine (Sta), lamivudine (Lami) and zidovudine (Zido).
The proposed research project
Background
Urine as a resource
Source separation of urine
In addition, urinal systems would require retrofitting plumbing systems to existing conventional systems, increasing the cost of the overall urinal system (Udert et al., 2003a). However, separate collection of urine also allows better treatment of pharmaceutical substances found in urine (Larsen et al., 2001).
Pharmaceutical removal in urine
Waterless urinary systems experience pipe blockages due to precipitation of pooled urine, and lack of regular maintenance can lead to odor problems (Hellstrom et al., 1999; Hashemi et al., 2015).
Significance of the research
Problem statement
Research questions
What is the percentage of drug and urea degradation due to hydroxyl radicals generated by hydrodynamic cavitation treatment at low pH (pH 2) and high pH (pH 12.4).
Hypothesis
Scope and limitations
Furthermore, pharmaceutical degradation and urea retention were quantified in relative rather than absolute terms. The following assumptions were made for the current work: conventional drugs and over-the-counter antiretroviral drugs were selected based on availability and did not necessarily represent drugs commonly found in wastewater, particularly urine;.
Urban water
Urban water challenges
However, cities experience frequent waterlogging due to an increase in impervious surface caused by rapid urban growth (Xia et al., 2017).
Urban water solutions
The connection between wastewater, nutrients, energy and water offers opportunities to drive a more sustainable urban water cycle (Volpin et al., 2018). As much as 80% of the water used came from rainwater collection, seawater desalination and recycled water (Rygaard et al., 2011).
Urine as a resource
In addition, wastewater could be used as a valuable resource (Sikosana et al., 2017), as some wastewater streams also contain essential resources that can be used for fertilizer production (Qian, 2016). It has been shown that source-separated urine can be used similarly to mineral fertilizers, organic fertilizers, sewage sludge and source-separated solid waste compost (Jonsson et al., 1997).
Source separation of urine
- Benefits of source separated urine
- Public perception of urine source separation technologies
- Challenges of source separated urine
- Technologies for source separated urine
The inorganic salt precipitation of the collected urine then causes blockages in the urine collection system (Hashemi et al., 2015). As a result, it was recommended to use source-separated urine in the agricultural sector as a fertilizer source (Höglund et al., 2002).
Urea hydrolysis
The hydrolysis of urea poses challenges for the storage, transport and administration of urine, as urea hydrolysis causes mineral abrasion in bathroom fixtures, pipes and storage tanks (Ray et al., 2018). Furthermore, the ratio between ammonia and ammonium is influenced by the composition of the urine (Leyva-Ramos et al., 2004).
Stabilization of urine
Acidification
Ray et al (2018) proposed a method of using acid inhibitors used in waterless urinals. Alternatively, a single dose of sulfuric/acetic acid and OOMW, shown in the study by Hellstrom et al. (1999) and Aguilar (2011), acidified urine samples for more than 100 days and six months, respectively (Hellstrom et al. ., 1999; Aguilar , 2011).
Alkalinization
It was discovered that a temperature below 40 °C is optimal for stabilization of fresh urine by Ca(OH)2 (Randall et al., 2016). When the temperature is above 55˚C, the enzymatic urea hydrolysis is inactivated, and only the chemical urea hydrolysis occurs (Randall et al., 2016).
Nutrient recovery from source separated urine
Volume reduction methods
Reducing urine volume provides a sustainable way to manage urine reuse (Lind et al., 2001). Although urine represents only 1% of the total volume of domestic wastewater (Spångberg et al., 2014), reduction methods for source-separated urine still need to be considered.
Nutrient recovery technologies
It was recommended that the optimization of the hydrophobic gas separation system could become a competitive alternative nutrient recovery method (Nagy et al., 2019). This method was shown to be effective in recovering nutrients in source-separated urine (Lind et al., 2001).
Pharmaceuticals in the environment
The occurrence of pharmaceuticals in the environment
Although the concentration levels are below the toxic level, a chronic level must be determined to assess the long-term effects of the presence of pharmaceuticals in the environment (Calisto and Esteves, 2009). Pollution resulting from the presence of pharmaceuticals in the environment is different in each country due to preferred treatment options and market availability.
The fate of pharmaceuticals in the environment
An environmental burden system was developed to quantify the number of pharmaceuticals present in the environment. In addition, controlling and limiting the source of drugs would be effective in reducing the presence of drugs in the environment (Li, 2014).
Pharmaceutical removal methods
- Biological removal methods
- Membrane separation methods
- Chemical oxidation methods
- High and low pH methods
- Granular activated carbon methods
- Hydrogen peroxide methods
- Hydrodynamic cavitation methods
Rostvall and co-workers (2018) studied the removal efficiency of five different absorbents (sand, lignite, Xylit, granular activated carbon (GAC) and GAC + Polonite®) for the removal of 83 selected micropollutants (including pharmaceuticals). Stavudine A study by Dunge and coworkers (2004) showed that stavudine degraded when exposed to hydrogen peroxide (Dunge et al., 2004).
Pharmaceutical analysis methods
High performance liquid chromatography
The pH of the solution is an important parameter influencing the degradation of micropollutants (Madhu et al., 2015). Another study by Ghaly and colleagues (2014) looked at the degradation of orange IV dye at pH 2 and pH 10. The study found that the optimal degradation for orange IV dye occurred at pH 2, while degradation at pH 10 alone was reached with 12.4% of the degradation at pH 2 (Ghaly et al., 2014).
Ultraviolet spectroscopy
The stationary phase particles are packed inside the HPLC column and held in position by glass fiber columns with a layer of inert alkyl silane molecules. Therefore, HPLC instruments are made of stainless steel to withstand high pressure. The retention time for the solute is then determined for the analysis of the components in the solute for a column operating under specified conditions (Faust, 1997).
Motivation for the current study
The pharmaceutical analytical methods are described in Section 3.1, while the secondary pharmaceutical analytical method used for the current work is given in Section 3.2. In addition, the urinalysis method and pH analysis are described in section 3.3 and 3.4, respectively. Pharmaceutical removal methods are described in Section 3.5, including Section 3.5.5, which provides details for an optimized hydrodynamic cavitation system.
HPLC analysis methods
HPLC analysis method for OTCs
Chromatographic separations were performed at 35°C using 15 mM phosphate buffer pH 3.25 (solvent A) and acetonitrile (solvent B) as the mobile phase with gradient elution at a flow rate of 1 ml min-1.
HPLC analysis method for ARVs
HPLC analysis method for both OTCs and ARVs
UV spectroscopy
Analysis of urine
Analysis of pH
Pharmaceutical removal methods
- High pH removal method
- Granular activated carbon removal method
- Hydrogen peroxide removal method
- Hydrodynamic cavitation system
- System optimization for hydrodynamic cavitation
The concentration of urea and ammonium before and after the experiment were analyzed using the Discrete Gallery Analyzer (described in Section 3.3) to determine the percentage of degradation. The concentration of urea and ammonium before and after the experiment was analyzed using the Discrete Gallery Analyzer (described in Section 3.3) to determine the percentage of degradation. UV spectroscopy, instead of HPLC, was used to analyze the samples for paracetamol degradation.
Summary of experiments
Research method challenges
High pH
Further analysis showed that the degradation of tenofovir (an antiretroviral drug) was almost instantaneous due to the high pH. The degradation of tenofovir is attributed to a P–O in its structure (see Figure 7), which undergoes hydrolysis under basic conditions (Berger and Wittner, 1966). Therefore, the difference in the pharmaceutical structures leads to the difference in the breakdown of the drugs.
Granular activated carbon
The respective abbreviations of the pharmaceutical products represent the following pharmaceutical products: paracetamol (Para), salicylic acid (Sali), chlorpheniramine maleate (Chloro), diclofenac (Diclo), clopidogrel (Clopi). The respective drug abbreviations represent the following drugs: stavudine (Sta), lamivudine (Lami), zidovudine (Zido), abacavir sulfate (Aba), and nevirapine (Nevi). The difference in the degradation of the drugs by the different GAC grain sizes was small.
Hydrogen peroxide
The degradation of the ARVs due to hydrogen peroxide is represented in the chromatograms (shown in Figure 20). The results suggested that the exclusive use of the hydrogen peroxide together with calcium hydroxide is not suitable for the degradation of pharmaceuticals. The combined use of hydrogen peroxide and ultraviolet (UV) is one such way as proven by Wols and colleagues (2013).
Hydrodynamic cavitation
The combined effect of hydrogen peroxide in a high pH environment was ineffective for the degradation of the pharmaceuticals investigated for this work. Therefore, the HC system operated at a high pH was ineffective in degrading pharmaceuticals over a 30-min period. Therefore, a low pH was ideal for the oxidation of pharmaceuticals by hydroxyl radicals.
Optimized hydrodynamic cavitation system .1 Pharmaceutical degradation
- The effect of temperature and pH
- Cavitation device
- Inlet pressure
- Effect of temperature
- Practical application of the hydrodynamic cavitation system
Optimization of the HC system was considered for this work, as it also retained more than 90% urea (see section 4.6). There is concern about the temperature rise of the urine sample solution when using the HC system. In addition, no precipitation occurs at a low pH. The final stage will be an evaporation process to concentrate the urine solution instead of reverse osmosis.
Urea conservation results
Pathogens and pharmaceuticals in source-separated urine in eThekwini, South Africa', Water Research, 85, pp. 2019) 'Opportunities for building-scale urine division and challenges for implementation', Accounts of Chemical Research, 52(4), pp. Royal Society of Chemistry, 4, pp. 2010) 'Struvite precipitation from urine – Influencing factors on particle size', Water Research, 44(6), pp. 2018) 'Removal of pharmaceuticals, perfluoroalkyl substances and other micropollutants from wastewater using lignite, Xylit, sand, granular activated carbon (GAC) and GAC+. A review,' Sustainable Environment Research, 27(3), pp. 2002) 'Wastewater treatment: a novel energy efficient hydrodynamic cavitational technique', Ultrasonics - Sonochemistry, 9(3), pp.
2018) 'Application of hydrodynamic cavitation reactors for the treatment of wastewater containing organic pollutants: intensification using hybrid approaches', Fluids, 3(98), pp. 1999) 'Treatment of liquid effluents from dairy cattle and pigs by reverse osmosis', Journal of Agricultural Engineering Research, 73(2), pp. 2016) 'Dewatering of source-separated human urine for nitrogen recovery by membrane distillation', Journal of Membrane Science, 512, pp. Kosiac: Springer International Publishing AG. 2016) 'Beyond target 6.3: a systems approach to rethinking sustainable development goals in a resource-scarce world', Engineering, 2(4), pp. 2006) 'Pharmaceuticals in the environment in Italy: causes, incidence, consequences and control', Environmental Science and Pollution Research, 13, pp.
Sample description
Separation goals
The level of precision for the sample analysis was sufficient for the integration of the areas (under the chromatogram) to derive the concentration of the pharmaceuticals. The samples were used as a reference for the analysis of the samples from the pharmaceutical removal method experiments. The samples analyzed for each pharmaceutical removal method were as follows: blank urine sample, spiked untreated urine sample and the treated urine sample.
Sample pre-treatment and detection
The analyzed samples were as follows: pure water sample and urine sample, both of which were used as negative controls, individual drugs in water, individual drugs in urine, pharmaceutical mixture in water and pharmaceutical mixture in urine (used as positive). controls).
Developing the separation
Although the parameters for the initial HPLC methods used for the current work were based on the work of Patel and co-workers (2013), a similar thought process described by Snyder and co-workers (1988) was applied to HPLC method development. Reversed phase HPLC, which is commonly used, was used for the HPLC methods developed for this work. The present work examined the acidity and basicity of pharmaceuticals and their polarity to find the order of elution and the required mobile phases.
Method development
A chromatogram for the HPLC method for ARV testing is shown in Figure E4. Pharmaceutical products listed in the chromatogram: stavudine (Sta); lamivudine (Lami); zidovudine (Zido); abacavir sulfate (Aba);. Pharmaceutical products listed in the chromatogram: paracetamol (Para); chlorphenamine maleate (Chor), lamivudine (Lami), zidovudine (Zido), and stavudine (Sta).
Improving the separation
Repeatable separation
The energy required to operate the optimized hydrodynamic cavitation (HC) system was calculated to determine whether using the optimized HC system to break down pharmaceuticals is economical. 𝐸𝑃 = 𝑧𝑔, where 𝑧 is the relative position of the sample solution and 𝑔 is the acceleration of gravity. Once the pumphead was calculated, the force of the fluid would be determined, after which the energy required to operate the hydrodynamic cavitation (HC) system under the optimized conditions would be quantified.
