Waste Water Treatment Investigation and System Design Recommendation

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River Resilience Textile Company Waste Water Treatment
Investigation and System Design Recommendation
Student’s Name
Institutional Affiliation
Date

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Abstract
This report presents the findings for the task commissioned by the River Resilience Textiles
Company, to carry out testing of wastewater samples for the identification of heavy metals
and organic compounds. The heavy metals under investigation were arsenic and chromium
ions in the wastewater from the factory. In addition, the water was projected to contain
organic compounds such as dyes and possibly, some bacteria. From the literature, and
research on the possible sensing electrodes that could be effectively used to detect the
specified metals, polyvinylferrocene (PVF) electrodes which are metallopolymer-based were
identified as the effective choice. These electrodes have high selectivity for heavy metal
oxyanions and are effective under a range of different concentrations and electrolytic
conditions. For the removal of the organic dyes, a metal-organic framework was proposed.
The framework works through adsorption. The final process was the elimination of bacteria
by using a ceramic filter impregnated with silver ions.
Introduction
The textile industry is a consumer of huge water quantities needed in wet treatment
and the process of finishing textile materials. Textile production involves a complicated chain
of processes including spinning, knitting, and weaving. Assorted types of reagents are
utilized by these process such as bleaching and dyeing chemicals (Kos, Michalska, and Żyłła,
2016). The water discharged from these processes contains significant levels of different
pollutants. If discharged to the environment without prior treatment, it poses serious pollution
threat and health issues. Traditionally, the toxicity of wastewater was judged by the effect it
had on living organisms (biological effects) and the coloration of water bodies near textile
industries due to pollution. However, currently, the trend has shifted and the presence of

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hazardous chemicals in water can be easily identified using modern detection apparatus.
General guidelines have been formulated to regulate the levels of certain substances in
wastewater from industries. The contamination of water by heavy metals is a serious global
issue.
Several bodies such as World Health Organization (WHO) and the United States
Environmental Protection Agency (EPA) have established limits of heavy metals in water,
beyond which water is considered unsafe for human and animal consumption. The table
below outlines the permissible limits of certain heavy metals common in wastewater samples.
Metal EPA WHO
Copper (mg/l) 1.3 1.0
Mercury (mg/l) 0.002 0.001
Lead (mg/l) - 0.05
Cadmium (mg/l) 0.005 0.005
Contaminant detection system
Several traditional methods have been applied to detect heavy metal ions in water.
These include atomic absorption spectroscopy (AAS), high performance liquid
chromatography (HPLC), flame atomic absorption spectrometry and wet chemical technique
including titrimetry and colorimetry (Bansod, Kumar, Thakur, Rana, and Singh, 2017).
However, according to Pujol et al., (2014), these methods require sophisticated and expensive
equipment with the necessity of trained staff which makes them unsuitable for use in on-site
applications. Electrochemical methods offer a better alternative as they have several
advantages such as rapid response, low cost, simpler approach and higher sensitivity. The

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configuration and the working principle of an electrochemical sensor is quite simple. A
common setup consists of three electrodes designated the working electrode (WE), the count
electrode (CE) and a reference electrode (RE) as shown in figure 1 below. The setup can be
configured to detect different metals by the simple modification of the working electrode
(changing its material). The electrodes are immersed in the solution whose metal
concentration is to be determined. If heavy metals are present in the solution, certain
characteristics of the circuit such as the current flowing through the electrodes, the potential
difference between the electrodes. Electrochemical impedance electrochemiluminescence and
capacitance change hence the identity and concentration of different metals can be
determined.
Figure 1: Electrochemical setup for metal ion detection
Different materials have been explored for use in the fabrication of the sensing
electrodes. Carbon-based materials have been widely investigated as ideal candidates for use
as heave metal detection electrodes. This is due to their many excellent mechanical and

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electrical properties such as superior electrical conductivity (Shimizu, Braunger, and Riul
2019). In particular, carbon nanotubes have been given great attention since their invention.
These have high electrolytic activity, large surface for effective detection and low electrode
fouling (Gumpu, Sethuraman, Krishnan and Rayappan 2015). Metal oxides such as zinc
oxide, magnesium oxide, and hematite have also been widely applied to detect heavy metals
in solutions since they exhibit excellent nano-morphological properties. These metal oxides
have enhanced adsorption capacity, high electron transfer capability, and catalytic properties.
In addition, they are non-toxic and biocompatible.
Studies have demonstrated the suitability of re-dox active electrodes for the detection
of heavy metals as a result of their electronic tenability and their high molecular selectivity.
In this case, the requirements of the detection system are the ability to detect both heavy
metals including arsenic and chromium and organic components (dyes and nitrophenols).
Since the elements present in the discharge water are already known, this makes the selection
of a detection system easier unlike in most practical cases in which the components to be
detected are not established. After the identification of the appropriate electrochemical setup,
with the appropriate sensing electrodes, an experiment must be conducted using a sample of
the wastewater to be treated to establish the accuracy of the system and its detection limits.
To be able to prove that the water is safe for discharge to the environment, it is necessary to
progressively monitor the concentrations of the metals and organic components before and
after the treatment. There are various types of electrodes that can be used to detect both
chromium and arsenic elements simultaneously (Su et al., 2018). In this detection and
treatment system, two different approaches will be implemented to detect metal ions using
one type of electrodes and organic waste using a different method. Polyvinylferrocene (PVF)

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electrodes, which are based on metallopolymer have been showed to have excellent
selectivity of heavy metal oxyanions and fast electron transfer. In addition, they have high ion
uptake capacity for organic contaminants (Su et al., 2018). Therefore, PVF electrodes will be
used in the detection of arsenic and chromium ions.
Organic waste removal and filtration
For the detection of the organic dyes, a different approach is proposed. According to
Kos, Michalska, and Żyłła (2016), water quality is highly affected by color. Even small
quantities of dyes are visible and most of them are toxic and carcinogenic. The degradation of
dyes is difficult due to their high stability on exposure to light and oxidation reactions.
Various methods have been proposed for the removal of dyes and organic materials from
water. These include chemical, biological and physical approaches. However, the most
common technique uses adsorption. Materials that can be used in this process include
crystalline materials such as metal organic frameworks (MOFs). Despite the fact that these
materials have not been widely applied in the detection of dyes, in a study by Haque, Jun, and
Jhung (2011), it was shown that iron-based MOFs had higher adsorption capacities than
activated carbon. Additionally, MOFs are flexible and dynamic and their shape and pore size
can be easily altered. Therefore, iron-based MOF is proposed for the removal of the organic
dyes present in the water. Specifically, it is suggested that MOF−23 5 which is a
terephthalate should be used. MOF−235 is capable of absorbing both anionic and cationic
dyes in the liquid phase. This makes it ideal for use in the elimination of different types of
organic dyes in the wastewater.
Bacterial removal

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To keep the cost of the system low while maintaining efficiency, it is suggested that a
ceramic water filter (CWF) should be used to eliminate the suspected bacteria in the
wastewater. According to igoli, Dorraji, and Amani-Ghadim (2017) CWF are capable of
eliminating 90 to 99 % of bacteria from water and 99 % of protozoa. To improve the
effectiveness of the filter, silver nanoparticles and silver nitrate are usually added to the filter
due to their antimicrobial properties. From literature, the concentration of silver in CWFs
varies from 32 to96 mg. It is recommended to use about 64 mg of silver nanoparticles per
ceramic water filter (Figoli, Dorraji, and Amani-Ghadim, 2017). Bacterial disinfection by
CWFs can be achieved in two ways. Microorganisms can be eliminated through adsorption or
exclusion by size. Alternatively, the microorganisms may be eliminated through inactivation
by silver ions or silver nanoparticles. Figure 2 below shows bacteria trapped in a ceramic
water filter enriched with silver nanoparticles.
Figure 2: Bacteria trapping in a ceramic water filter enriched with silver nanoparticles.

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Since silver may be a pollutant itself, its desorption from the coated filter should be low.
Silver desorption has been reported in some studies during the initial water flushes. Some
studies have investigated the use of a phosphate buffer as an influent solution, achieving
reduced silver concentration in the effluent to below the maximum allowed contaminant level
of about100 ppb.
Figure 3: Block diagram of the proposed treatment system
Conclusion
It was suggested that Polyvinylferrocene (PVF) electrodes, which are based on
metallopolymer be used for the detection of arsenic and chromium ions due to their high
selectivity for heavy metal oxyanions. For the removal of organic dyes, an iron-based metal
organic framework (MOF−235 ¿ was identified as the ideal elimination material due to its
ability to absorb both cationic and anionic dyes. Finally, for bacteria removal, it was
suggested that a ceramic filter should be employed. For improved efficiency, the ceramic
filter should be impregnated with silver ions.

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