Polycyclic aromatic hydrocarbons (PAHs) in Greater Cairo water supply systems.

Polycyclic aromatic hydrocarbons (PAHs) pose a constant threat to the environment and public health. There are numerous activities in the Greater Cairo area that emit and release significant amounts of PAHs. Concentrations of these PAHs are released into the air and mixed with surface water, limiting its use. In this study, 17 PAH compounds are mapped at eight sites along the Nile River and its tributaries in Greater Cairo. In addition, their removal efficiency is evaluated with the conventional treatment in eight water treatment plants. PAHs were analyzed using GC-MS from January to December 2018. Naphthalene, anthracene, fluorene, pyrene, and phenanthrene were detected. The total amount of PAHs in raw water was highest in Shamal Helwan (1,325 ± 631 ng/l) and lowest in Mostorod (468 ± 329 ng/l), and the removal ranged from 25 to 31%. Further research is needed to integrate other techniques to reduce PAHs using the conventional treatment, and more efforts should be made to reduce the presence and release of PAHs in raw water.

Aluminum sulfate regeneration from surface water treatment waste in Cairo, Egypt.

The world needs to adapt to recycling and reusing water due to limited resources. So, decision-makers and policy leaders should use sustainable practices to improve protection and pollution remediation. Aluminum sulfate is used for surface water treatment, which leads to waste sludge being disposed into water bodies, causing environmental pollution. Coagulants' regeneration from sludge improves water quality and reuse options. Organics accumulation is the primary concern regarding coagulant regeneration, using acidification. Our study investigated the raw water quality, aluminum sulfate, and sludge and evaluated its influence on coagulant recovery, using acidification, from eight water treatment plants (WTPs) in Cairo, Egypt. The significant elements in the tested sludge were aluminum with a concentration range of 86.65-688.85 mg/g sludge in El-Rawda and Embaba and iron with a concentration range of 9.45-7.45 mg/g in Shamal Helwan and El-Fostat. Recovery percentages of aluminum, iron, manganese, and strontium recorded the highest values 97%, 89%, 89%, and 92% for Embaba, Rod El-Farag, Embaba, El-Rawda, respectively. The correlation between metal concentration and recovery was insignificant in the studied matrix and conditions for the four metals. Total organic carbon (TOC) transfer into recovered solutions was maximum in El-Fostat (82.6%) and minimum in Embaba (36.7%). The TOC transfer percentage depends on the matrix of the sludge. The best location for coagulant recovery is at the Embaba WTP, where there were minimum organics transfer and maximum Al recovery.

Repeated Aluminum Sulfate Recovery from Waterworks Sludge: A Case Study in El-Sheikh Zaid WTP.

Although surface water treatment presents a good solution for pollutants in rivers and freshwater lakes, the purification process itself presents a great threat to the aquatic environment through aluminum waste disposal. Recent studies have introduced coagulants recovery from treatment sludge as a green solution for waste handling and cost reduction. This article aims to evaluate repeated aluminum coagulants recovery from sludge using sulfuric acid. The waste from El-Sheikh Zaid Water Treatment Plant (ESZ-WTP) was characterized, then sequential coagulants recovery using optimum conditions was conducted. In addition, treated water was analyzed to determine the efficiency of the obtained coagulants and their influence on treated water quality. Sequential coagulants recovery using acidification revealed that no metals accumulation took place in the produced coagulants until the third recovery from ESZ-WTP sludge. On the other hand, a noticeable increase in trihalomethanes was detected in the treated water, especially using the third recovered coagulant. In conclusion, sequential coagulants recovery and usage in water treatment is an attractive alternative for single-use original coagulant in ESZ-WTP but for no more than three sequential recoveries. It is advisable to apply a fresh coagulant every three sequential recoveries to enrich the aluminum content and regenerate the sludge before restarting the recovery process.

Evaluation of leached metals in recovered aluminum coagulants from water treatment slurry.

The water treatment industry consumes large quantities of coagulant and produces huge amounts of slurry. The cost of alum used in water treatment, stringent regulations and negative impacts of sludge disposal are the motive to do integrated research studies on the technical feasibility of aluminum coagulant recovery from sludge using acidification. This work studied the leaching of iron, manganese, and chromium as the most extracted metals with aluminum during sludge acidification; furthermore, these metals have a great impact on the recovered coagulants' efficiency and treated water quality. The sludge used was collected from El-Sheikh Zayd water treatment plant in Egypt, then dried and ground; afterward, the effect of acid concentration, sludge mass, temperature, mixing speed and mixing time was studied. In addition, it was noticeable that the efficiency of sulfuric acid in leaching iron, manganese and chromium is higher than that of hydrochloric acid. Also, higher leaching for the three metals was obtained in all the experiments using higher acid concentration, elevated temperature, and rotational speed. Finally, the leached metals in recovered aluminum coagulants will not limit its application to water and wastewater treatment, as their concentrations are still very low if compared with aluminum, even with the highest leaching efficiency.

Beneficial effects of oxygen addition and hybrid poplar phytoremediation of petroleum-contaminated soils.

Laboratory scale experiments were conducted to investigate the effect of a phytoremediation system using poplar trees on the smear zone-soil gases for petroleum hydrocarbons contaminated soil. Eight clear polyvinyl chloride (PVC) columns (1.5 mx0.1 m) were packed with the contaminated soil covered with clean top soil. Five ports were installed on the front side of each column for soil gas sampling. Hybrid poplar trees (Populus deltoides X nigra DN34) were grown in 4 columns. The remaining four columns were used as controls (no trees). Three of the tree columns and 3 of the controls had induced air flow. An experimental apparatus was established to allow for the induced air to flow through the air flow columns. Average air flow rates of 0.43 L/d, 0.71 L/d and 1.50 L/d were tested. The columns were operated for 78 days. During the experiments, the effect of oxygen addition, through the induced air, on the development of poplar roots in the hydrocarbons contaminated soil was investigated. In addition, the compositions and concentrations of the soil gases at different soil depths were evaluated during the course of the experiments.

Assessments of the efficacy of a long-term application of a phytoremediation system using hybrid poplar trees at former oil tank farm sites.

A poplar tree-phytoremediation system was installed at former refinery and tank farm sites in Cabin Creek, West Virginia, to cleanup petroleum-contaminated-soils and groundwater. Groundwater and soils in both sites were sampled and analyzed on a regular basis to monitor changes in contaminant concentration since 1999. The concentration of benzene, toluene, ethylbenzene, xylene, and gasoline range organics (GRO) decreased an average of 81%, 90%, 67%, 78%, and 82%, respectively, in the lower soil horizons and 34%, 84%, 12%, 19%, and 59%, respectively, in groundwater. In addition, concentrations of oxygen, methane, and carbon dioxide in soil gas demonstrated that tree roots dewatered soils and allowed penetration of oxygen deep into the soil profile, creating necessary conditions for rhizosphere bioremediation. Although required clean-up time can limit phytoremediation, it has proven to be a cost-effective strategy for site improvement if imminent pathways for human exposure and risk are not an issue.

Treatment of combined sewer overflow using retention treatment basin assisted with polymer chemical coagulation.

Pilot plant experiments were conducted to examine the performance of a retention treatment basin (RTB) with chemical coagulation using a cationic polymer in the treatment of combined sewer overflow (CSO) for the City of Windsor, Ontario, Canada. The pilot plant was operated at surface overflow rates (SORs) up to 1370 m3/m2 x d. This study demonstrated that the use of polymer coagulation improved settling characteristics of solids, and allowed the SOR in the RTB to be increased significantly. An optimum polymer dosage to achieve the discharge standards of CSO was determined from the experimental runs. The effluent quality met the Ontario Ministry of the Environment Procedure F5-5 in terms of 5-day biochemical oxygen demand and total suspended solids removals. A flushing box was successfully tested for flushing the collected floatables and sludge from the bottom of the RTB after storm events.

Modeling of heavy metals removal from municipal landfill leachate using living biomass of water hyacinth.

Water Hyacinth, Eichhornia crassipes, a fast-growing floating aquatic macrophyte; was used for the removal of heavy metals from a municipal landfill leachate. The leachate was spiked with different mixtures of five heavy metals (Cd, Cr, Cu, Pb and Ni), at a range of concentrations to cover the ranges reported in literature. The initial concentrations of the total heavy metals in leachate ranged from 0.06 to 5.5 mequiv L(-1). All experiments were carried out in batch reactors in a greenhouse environment. The water hyacinth plants showed a very promising ability to remove and accumulate these metals from the leachate (24% to 80% removal of total heavy metals). Generally, the reduction in concentration of total heavy metals followed two distinct patterns, a rapid initial decrease followed by a slower decrease. An exponential mathematical model was established to estimate the remaining concentration of total heavy metals in the leachate over time for the rapid initial decrease. Also, a linear relationship was established to estimate the concentration of total heavy metals over time for the slower decrease. In addition, Langmuir and Freundlich isotherms were applied to the observed data and the constants of each isotherm were obtained.