https://cyberleninka.org/article/n/567486.pdf

A review on polycyclic aromatic hydrocarbons: Source, environmental impact, effect on human health and remediation

One of our era's greatest scourges is air pollution, on account not only of its impact on climate change but also its impact on public and individual health due to increasing morbidity and mortality. There are many pollutants that are major factors in disease in humans. Among them, Particulate Matter (PM), particles of variable but very small diameter, penetrate the respiratory system via inhalation, causing respiratory and cardiovascular diseases, reproductive and central nervous system dysfunctions, and cancer. Despite the fact that ozone in the stratosphere plays a protective role against ultraviolet irradiation, it is harmful when in high concentration at ground level, also affecting the respiratory and cardiovascular system. Furthermore, nitrogen oxide, sulfur dioxide, Volatile Organic Compounds (VOCs), dioxins, and polycyclic aromatic hydrocarbons (PAHs) are all considered air pollutants that are harmful to humans. Carbon monoxide can even provoke direct poisoning when breathed in at high levels. Heavy metals such as lead, when absorbed into the human body, can lead to direct poisoning or chronic intoxication, depending on exposure. Diseases occurring from the aforementioned substances include principally respiratory problems such as Chronic Obstructive Pulmonary Disease (COPD), asthma, bronchiolitis, and also lung cancer, cardiovascular events, central nervous system dysfunctions, and cutaneous diseases. Last but not least, climate change resulting from environmental pollution affects the geographical distribution of many infectious diseases, as do natural disasters. The only way to tackle this problem is through public awareness coupled with a multidisciplinary approach by scientific experts; national and international organizations must address the emergence of this threat and propose sustainable solutions.

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Environmental and Health Impacts of Air Pollution: A Review.

Polycyclic aromatic hydrocarbons (PAHs) include a group of organic priority pollutants of critical environmental and public health concern due to their toxic, genotoxic, mutagenic and/or carcinogenic properties and their ubiquitous occurrence as well as recalcitrance. The increased awareness of their various adverse effects on ecosystem and human health has led to a dramatic increase in research aimed towards removing PAHs from the environment. PAHs may undergo adsorption, volatilization, photolysis, and chemical oxidation, although transformation by microorganisms is the major neutralization process of PAH-contaminated sites in an ecologically accepted manner. Microbial degradation of PAHs depends on various environmental conditions, such as nutrients, number and kind of the microorganisms, nature as well as chemical property of the PAH being degraded. A wide variety of bacterial, fungal and algal species have the potential to degrade/transform PAHs, among which bacteria and fungi mediated degradation has been studied most extensively. In last few decades microbial community analysis, biochemical pathway for PAHs degradation, gene organization, enzyme system, genetic regulation for PAH degradation have been explored in great detail. Although, xenobiotic-degrading microorganisms have incredible potential to restore contaminated environments inexpensively yet effectively, but new advancements are required to make such microbes effective and more powerful in removing those compounds, which were once thought to be recalcitrant. Recent analytical chemistry and genetic engineering tools might help to improve the efficiency of degradation of PAHs by microorganisms, and minimize uncertainties of successful bioremediation. However, appropriate implementation of the potential of naturally occurring microorganisms for field bioremediation could be considerably enhanced by optimizing certain factors such as bioavailability, adsorption and mass transfer of PAHs. The main purpose of this review is to provide an overview of current knowledge of bacteria, halophilic archaea, fungi and algae mediated degradation/transformation of PAHs. In addition, factors affecting PAHs degradation in the environment, recent advancement in genetic, genomic, proteomic and metabolomic techniques are also highlighted with an aim to facilitate the development of a new insight into the bioremediation of PAH in the environment.

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Current State of Knowledge in Microbial Degradation of Polycyclic Aromatic Hydrocarbons (PAHs): A Review

Solid waste issue: Sources, composition, disposal, recycling, and valorization

Removal of heavy metal from industrial wastewater using modified activated coconut shell carbon

Membrane bioreactor (MBR) technology has become a key component in water reclamation schemes for nearly 30 years due to the possibility of providing high quality water. The objective of the present study is to investigate the efficiency of MBR for the treatment of municipal blackwater. A pilot-scale MBR unit was installed and operated in the NRC, Egypt. Blackwater was primary treated through three chambers baffled sedimentation tanks. The effluent was then directed to the MBR. The reduction in the MBR permeates for COD and BOD ranged from 90 to 94% and from 90 to 97%, successively. The corresponding level of COD ranged from 34 to 76 mg/l, and BOD ranged from 6 to 18 mg/l. The average removal rate of ammonia and TKN was 97% and 94%, respectively. The averages values of some parameters in permeate were as follow: TSS, 0.6 mg/l; COD, 42 mg/l; BOD, 10 mg/l; NH 3 -N, 5.8 mg/l. This indicates the advantages of membrane filtration over the ac tivated sludge processes. Therefore, MBR process was found to be efficient for improving effluent quality. Such performance will guide the decision maker on the potential of MBR application and advantages of efficient wastewater treatment for irrigation purpose in Egypt.

Membrane bioreactor for the treatment of municipal blackwater in Egypt

Innovative reuse of drinking water sludge for the treatment of petroleum produced water to enhance oil recovery

It is well known that pH is the controlling factor for solubility of metals, which is affected by the “law of chemical solubility product constant” (ChSP). The present investigation focuses on the fate of heavy metals resulted from the use of primary treated sewage water for irrigating edible plant in a local sewage farm. The studied plants are maize, green beans, and alfalfa. Extensive sampling program was designed to collect both irrigated water and plant samples every two weeks. The plant samples were partitioned into roots, stems, and leaves, as well as the grains of maize and been plants. The physical and chemical characteristics of irrigated water were determined. Level of heavy metals in sewage water and all plant samples was determined. It was found that the availability of metals to plant is, generally, governed by the law of ChSP constant. In present study, the pH of both irrigated water and the soil were within the slight alkaline medium which restricted the solubility of metals. Thus, negative impact on the accumulation of metals by the irrigated plants was detected. The level of metals in all the studied plant parts was within the permissible limits according to the WHO, FAO and the Egyptian regulations. This is mainly attributed to the limited solubility of metals at the slight alkaline medium according to the law ChSP constant. It was thus concluded that the availability of metals from both irrigated waters and soils were greatly restricted and controlled by the pH value. This explains the limited accumulation of metals by all studied plants. However, log-term irrigation with sewage will certainly result in a dramatic accumulation of metals by both soil and plants. It was recommended to restrict the reuse of disinfected tertiary treated water for irrigating vegetable plants according to the local regulations.

https://ejchem.journals.ekb.eg/article_48811_db63a06e7d111ab4c644cf152ca76a96.pdf

Fate of Heavy Metals in Selective Vegetable Plants Irrigated with Primary Treated Sewage Water at Slightly Alkaline Medium

The removal of nickel and mercury from drinking water, using powdered activated carbon (PAC) and granular activated carbon (GAC) was studied intensively. The water studied was artificially contaminated by Ni and Hg to yield 2mg/l each. Both batch and continuous systems were tested. The time needed to maintain equilibrium and the adsorption isotherm were determined by the batch system. The results obtained were found to be confirmed with Freundlich’s equation, rather than Langmuir or BET. When the PAC was used, the values 1/n and K were 1.59 and 1.02 for Ni and 1.21 and 1.91 for Hg. Relatively similar results were obtained when the GAC was examined. This indicated the stronger adsorbability of mercury compared to nickel. When investigating the continuous system at different contact times the results indicated that increasing the contact time increased the metal : carbon removal efficiency. The overall results showed that the breakthrough points for either Ni or Hg reflected their adsorption isotherms as indicated by k values. Concludes that the addition of an activated carbon filter is recommended for the treatment of drinking water contaminated by heavy metals.

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Adsorption of nickel and mercury from drinking water simulant by activated carbon

Examines the fate of heavy metals in sewage water and the sludge produced. Investigates the level of metals before and after the use of chemical coagulants as well as throughout every process of the plant. Results reveal that the present upgrading of the plant has a remarkable improvement in the performance of the sewage treatment. Concludes that such upgrading of the plant reduces sewage tax because of the improvement in performance. In addition, the hydrolysis of the pre‐treated sludge can improve the de‐nitrified process and therefore can save energy, while the application of lime can be a substitution for enlarging the plant itself.

Hussein I. Abdel-Shafy

Papers

Membrane bioreactor for the treatment of municipal blackwater in Egypt

Innovative reuse of drinking water sludge for the treatment of petroleum produced water to enhance oil recovery

Fate of Heavy Metals in Selective Vegetable Plants Irrigated with Primary Treated Sewage Water at Slightly Alkaline Medium

Adsorption of nickel and mercury from drinking water simulant by activated carbon

Fate of heavy metals via chemical‐biological upgrading of sewage treatment plant