Kinetics of Heavy Metals Adsorption on Gravels Derived From Subsurface Flow Constructed Wetland

Adsorption kinetics of Ni, Cr, and Pb on gravels collected from constructed wetland was studied at varied metal concentrations and contact period for estimating the removal of heavy metals from wastewater. Batch experiments were conducted by shaking 120 ml of metal solutions having 5 concentration levels each of Ni (1.0, 2.0, 3.5, 5.0 and 6.0 mg l-1), Cr (1.0, 2.0, 3.0, 4.5 and 6.0 mg l-1), and Pb (1.0, 3.0, 6.0, 8.0 and 12.0 mg l-1) with 50 g of gravels for as function of time. Adsorption of Ni, Cr, and Pb on gravels ranged from 34.8 to 47.2, 42.7-54.9, and 47.5-56.9%, indicating their removal in the order: Pb > Cr > Ni. Freundlich model showed a good fit for Ni and Cr (R2>0.9) while Langmuir model fitted better for Pb (R2= 0.7). The pseudo-second-order model showed the best fit to simulate the adsorption rates of these metals on gravel.

Technological Developments in the Determination of Emerging Contaminants in Water

Emerging contaminants (ECs), which constitute a group of chemicals, such as personal care products, food additives, and endocrine disruptors, are not commonly monitored and have the potential to cause adverse effects on the environment and humans. In water, even at low concentrations, they pose risks to environmental health. Several technologies have been developed to determine these compounds; the most common ones are liquid-liquid extraction (LLE), solid-phase extraction (SPE), solid-phase microextraction (SPME), stir-bar sorptive extraction (SBSE), and dispersive liquid-liquid microextraction (DLLME) with analysis by gas and liquid chromatography (GC and LC) coupled to mass spectrometry (MS). This chapter analyzes these methodologies and highlights their possibilities and limitations and compiles the most recent advances in this field.

Evaluation of Selected Reaeration Models for Water Quality Management

In this chapter, a new proposed model was compared with selected standard models and evaluated statistically (model of selection criterion [MSC] and Akaike information criterion [AIC]). Suspended concentration and calculated reaeration rate were used to predict concentration of EPs removable by the aeration and self-purification of the stream. The study revealed that MSC for the new proposed model were 0.75, - 0.44, - 0.32, - 0.45, and - 0.45 respectively. AIC for both dry and wet seasons were 11.85, 42.17, 41.37, 42.17, and 42.25 for the new proposed model, respectively. It was concluded the proposed model performed better than some of the standard models.

Electrochemical Treatment of Wastewater

This chapter presents an overview of over 529 articles on designs, models, laboratory setups, and applications of electrochemical processes from 1973 to 2017 with particular attention paid to the removal of emerging environmental pollutants. The chapter demonstrates that electrochemical and advanced oxidation processes are efficient despite the economic implications of the technologies. The electrodes in use arranged from monopolar to bipolar mode, which varies from the electroplating baths, recalcitrant organic contaminants, and eluates of an ion-exchange unit and the number of electrodes in a stack to a variant of rotating cathode cell. Application of the process can be in the form of a static anode and a rotating disk cathode. The narrow spacing between the electrodes in the pump cells allow the entrance of the effluent and effective wastewater treatment. It was concluded that electrochemical treatment techniques have a variety of laboratory setups and a wider range of applications.

Semiconductor Nanocomposites-Based Photoelectrochemical Aptamer Sensors for Pharmaceuticals Detection

Development of sensors for pharmaceuticals has become very essential. This is due to the need to monitor the release and toxicological effects of pharmaceuticals into the environment. In this work, the authors explored bismuth sulphide (Bi2S3) nanorods and graphene as photoactive material for constructing a photoelectrochemical (PEC) aptasensor for sulfadimethoxine (SDM) detection, exhibiting high sensitivity, stability, and reproducibility. In another experiment, Mo-doped BiVO4 (Mo-BiVO4) and graphene nanocomposites were explored as photoactive material to construct a visible light-driven photoelectrochemical biosensor. Graphene in the nanocomposites was very essential in immobilizing streptomycin aptamer through π-π stacking interaction. Finally, graphene doped CdS (GR-CdS) synthesized via one pot hydrothermal technique and gold nanoparticles (Au NPs) were employed to construct a PEC aptasensor for diclofenac (DCF).

Occurrence and Impact of Emerging Contaminants in Nigeria's Freshwater Resources

The presence of emerging contaminants (ECs) in freshwater presents a major challenge as they pose serious threats to human life and ecosystems. It is essential that water is of good quality before it can be used by communities and benefit the environment. Nigeria is blessed with abundant water resources; however, the country lacks effective and efficient institutions to provide sanitation services to treat domestic waste and to monitor and regulate industries, helping them protect the environment by ensuring they treat their industrial waste before discharging to the water bodies. Various ECs have been detected in the nation's freshwater resources. They pose significant threat to the environment, and they have the potential to harm aquatic life and human health. Nigeria needs a comprehensive and integrated water resources management plan that gives priority to the monitoring, detection, and treatment of emerging contaminants to mitigate against the potential risks that occur when they are present in freshwater resources.

Fabrication of Metal Oxide-Biopolymer Nanocomposite for Water Defluoridation

Fluoride contamination in groundwater affects about 150 million people worldwide. In this study, the authors focused on synthesizing biopolymer metal oxide nanocomposite for fluoride removal. Nanocomposite material was done using SEM. As(V), Al, Ti, Zr, and Fe water samples were analysed by ICP-MS (inductively coupled plasma-mass spectrometry). Fluoride level was determined using the standard method – Ion-Selective Electrode method. Preliminary results indicate arsenic (V) removal was below the 10 ppb and fluoride less than 1.5 ppm as prescribed by WHO. The removal efficiency was after 60-70 minutes with recyclability of 11 cycles. The nanocomposite worked well in all pH ranges 6.5-8.5. A filter cartridge biopolymer metal oxide nanocomposite constituting of template aluminium homogenized in the aggregated network of chitosan was developed as an adsorbent for fluoride from the water with better adsorption limit.

Chemicals of Emerging Concern in Surface and Wastewater

Rapid technological advancement in the pharmaceuticals and chemical industry has led to synthesis of compounds used for health/personal care and industrial products in large amounts. These chemicals of emerging concern (CECs) are consequently released into the environment through industrial emissions, disposal processes, and during use and application. Rapid population growth and urbanization within the Lake Victoria catchment region has inserted tremendous pressure on the environment and its resources, thus resulting to potential point and diverse sources of CECs introduction to the environment. Improper waste disposal and conventional wastewater treatment technology that are practiced in the catchment have not helped in prevention and removal of CECs and other pollutants from the environment. This chapter evaluates the occurrence of CECs mainly in surface and wastewater within the Lake Victoria catchment of Kenya and informs on the fate and diverse health effects that come with their presence in the environment.

Emerging Contaminants

This chapter discusses water pollution control and abatement strategies in relation to emerging contaminants. The pollution prevention measures described in the chapter can broadly be categorized into four main areas that are highly interdependent: behavioral changes, new technical solutions to aid remediation of the environment, further research and data availability, and legislation or policy reforms. These main areas have been expanded in detail under 13 subtitles that are not only interdependent but also practical and achievable. The chapter demonstrates that if the proposed measures are collectively taken into consideration, then most of the United Nations Sustainable Development goals, especially the goals relating to water quality, would become a reality. The benefits of pollution control and abatement are widespread and far-reaching and can better the quality of life on the planet.

Polycyclic Aromatic Hydrocarbon Compounds as Emerging Water Pollutants

Aquatic ecosystems are pivotal resources that nurture diverse life forms apart from providing different ecosystem services. Global pollution, directly and indirectly, depletes the quality and standards of these resources and hampers the animals residing there. The incomplete combustion of all sorts of organic substances found in nature produces and release an emerging group of contaminants known as polycyclic aromatic hydrocarbons (PAHs). There are over a hundred different kinds of PAHs known and 16 amongst them are regarded as priority pollutants including phenanthrene (PHE). PHE is abundantly found in the aquatic environment and poses a higher risk to animals. It causes a vast array of toxicities in aquatic animals including genotoxicity, cardiotoxicity, transgenerational toxicity, neurotoxicity, developmental toxicity, and potentially induces oxidative stress and behavioral alterations. However, many areas of PHE toxicity in aquatic organisms are yet to be properly understood and management measures are yet to be initiated.