Abstract
Abstract In this study, an oxygen-releasing and phosphorus-controlling agent (ORPC) consisting of calcium peroxide (CaO2), bentonite, cement, stearic acid (SA), citric acid (CA) and fine sand was synthesized successfully and used to purify phosphorus-rich river water. The removal of phosphorus using ORPC was studied in actual river water and the results found that over 75.0% phosphorus was removed by adding ORPC at 30 mL h−1 flow rate in initial phosphorus concentrations of 0.76 mg L−1. The ORPC was further used to evaluate the changes of aluminum phosphate (Al-P), ferric phosphate (Fe-P) and calcium phosphate (Ca-P) in sediment. Fe-P, Al-P, and Ca-P in the sediment increased from 0.14, 0.196, and 1.63 mg g−1 to 0.159, 0.372, and 2.74 mg g−1 respectively within 28 days, indicating that the total dissolved phosphorus in the overlying water could be adsorbed by ORPC and further transformed into Al-P, Ca-P, and Fe-P in the sediment, thus inhibiting the release of endogenous phosphorus in sediment to the water. In addition, the performance of ORPC with various contents of SA and CaO2 was investigated. In summary, ORPC can be employed to adsorb phosphorus in water and prevent phosphorus release from sediment, therefore achieving the purpose of controlling phosphorus and maintaining DO at a reasonable level.
Highlights
Eutrophication is considered to be the most significant water quality problem in water bodies worldwide, recently it has been improved to a certain extent (Smith & Schindler 2009; Zamparas & Zacharias 2014)
Compared with the infrared spectra of CaO2 powder and oxygen-releasing and phosphorus-controlling agent (ORPC) (Figure 2(a)), the O-O bond appeared in the CaO2 at 869 cmÀ1 and the O-O bond appeared at 875 cmÀ1 in the ORPC, which would contribute to releasing oxygen (Zegliński et al 2006)
The characteristic peak at 2,850 cmÀ1 in the ORPC was a long carbon chain structure that was derived from the stearic acid (SA), indicating the surface of CaO2 was covered by organic layers
Summary
Eutrophication is considered to be the most significant water quality problem in water bodies worldwide, recently it has been improved to a certain extent (Smith & Schindler 2009; Zamparas & Zacharias 2014). The phenomenon of eutrophication and black-odor are mainly related to the high concentration of phosphorus and low DO in the water body. Phosphorus is a main restrictive element that leads to the eutrophication of river water, controlling the concentration of phosphorus plays a key role in the governance of water resources (Schindler et al 2008; Zhu et al 2017). Though numerous applications have been taken to control the loading of external phosphorus, black-odor is still one of the most vital problems. The reason is that the loading of internal phosphorus in sediment still maintains the high concentration, which delays the recovery of eutrophic water bodies (Cooke et al 1993; Ding et al 2018). Solidphase material capping technology in in-situ repair technology is mostly favored because of its moderate cost and simple operation (Fan et al 2017; Wang et al 2017; Zhou et al 2018; Zhu et al 2019)
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