More than 170 million individuals have been influenced by arsenic (As) because of the ingestion of As-polluted groundwater. The presence of As in water bodies, particularly groundwater, has been found to become a widespread issue in the past few decades. Because arsenic causes extreme wellbeing impacts, even at a low concentration in drinking water, the innovations of As removal from contaminated water are of significant importance. Traditional strategies, for example, reverse osmosis, ion exchange, and electro-dialysis are generally utilized for the remediation of As-polluted water; however, the high cost and/or sludge production restricts their application in less-developed areas. The utilization of adsorbents acquired from natural materials has been explored as an alternative for the costly techniques for As removal. This paper aims to review the past and current developments in using naturals adsorbents or modified natural materials for arsenic removal and show the different parameters, which may influence the As removal effectiveness of the natural adsorbent, such as contact time, adsorbent dosage, flow rate, pH, reusability, temperature, and influence of others ions.

In this study, a modified horizontal settling tank with rotating biological discs was developed to treat slightly polluted surface water, and its performance on the simultaneous removal of turbidity, organics, and ${\mathrm{NH}}_4^{\mathrm{+}}$-N was investigated on a lab scale. Results show that the effluent quality of the modified settling tank is stable in more than two months of continuous operation. At a hydraulic retention time (HRT) of 2.0 h, 73.65 ± 5.15% turbidity, 53.98 ± 5.17% TOC, and 77.01 ± 10.02%, ${\mathrm{NH}}_4^{\mathrm{+}}$-N could be removed by the modified settling tank with an average of 1.96 NTU turbidity, 1.98 mg/L TOC, and 0.46 mg/L ${\mathrm{NH}}_4^{\mathrm{+}}$-N residue in the effluent. Due to the improvement in DO supply, higher removal efficiencies of both organics and ${\mathrm{NH}}_4^{\mathrm{+}}$-N were achieved with increased disc rotating speed (r < 4 r/min). Further study showed that the genus Hyphomicrobium dominant on the posterior discs and the genus Nitrospira dominant on the anterior discs mainly contributed to the enhanced bio-oxidation of organics and ${\mathrm{NH}}_4^{\mathrm{+}}$-N, respectively.

When desalinated water enters the existing drinking water distribution systems (DWDSs), the balance between water and scale will be destroyed, resulting in the release of iron and water quality problems, causing “yellow water”. This study investigated the inhibitory effects of pH, alkalinity, and phosphate on iron release and the optimal control condition using pipe section reactors with a response surface. For steel pipe, the optimal condition for iron release control was pH = 8.5, alkalinity = 250 mg/L CaCO₃, and phosphate = 0.1 mg/L. For cast iron pipe, the optimal condition was pH = 8.0, alkalinity = 250 mg/L CaCO₃, and phosphate = 0.1 mg/L. This study can provide theoretical support for subsequent water supply safety and lay a foundation for the water supply safety of the municipal pipe network.