Removal of coagulant aluminum from water treatment residuals by acid.
Sediment sludge during coagulation and sedimentation in drinking water treatment is called "water treatment residuals (WTR)". Polyaluminum chloride (PAC) is mainly used as a coagulant in Japan. The recycling of WTR has been desired; one method for its reuse is as plowed soil. However, WTR reuse in this way is inhibited by the aluminum from the added PAC, because of its high adsorption capacity for phosphate and other fertilizer components. The removal of such aluminum from WTR would therefore be advantageous for its reuse as plowed soil; this research clarified the effect of acid washing on aluminum removal from WTR and on plant growth in the treated soil. The percentage of aluminum removal from raw WTR by sulphuric acid solution was around 90% at pH 3, the percentage decreasing to 40% in the case of a sun-dried sample. The maximum phosphate adsorption capacity was decreased and the available phosphorus was increased by acid washing, with 90% of aluminum removal. The enhancement of Japanese mustard spinach growth and the increased in plant uptake of phosphates following acid washing were observed.
Environmental Research and Management Center, Hiroshima University, Japan. Electronic address: aqua@hiroshima-u.ac.jp.
Tetsuji
T
Okuda
Environmental Research and Management Center, Hiroshima University, Japan.
Wataru
W
Nishijima
Graduate School of Engineering, Hiroshima University, Japan.
Mayo
M
Sugimoto
Graduate School of Engineering, Hiroshima University, Japan.
Naoyuki
N
Saka
Graduate School of Engineering, Hiroshima University, Japan.
Satoshi
S
Nakai
Department of Architecture and Civil Engineering, Fukuyama University, Japan.
Kazuyasu
K
Tanabe
Agricultural Technology Research Center in Hiroshima Prefectural Technology Research Institute, Japan.
Junki
J
Ito
Agricultural Technology Research Center in Hiroshima Prefectural Technology Research Institute, Japan.
Kenji
K
Takenaka
Open University of Japan, Japan.
Mitsumasa
M
Okada
D000143:Acids / Q000737:chemistry*; D000327:Adsorption; D000535:Aluminum / Q000737:chemistry*; D000536:Aluminum Hydroxide / Q000737:chemistry*; D006863:Hydrogen-Ion Concentration; D010710:Phosphates / Q000737:chemistry; D059027:Recycling; D012987:Soil / Q000737:chemistry; D018724:Spinacia oleracea / Q000254:growth & development; D014865:Waste Disposal, Fluid; D014874:Water Pollutants, Chemical / Q000737:chemistry*; D018508:Water Purification / Q000379:methods*
D000143:Acids; D010710:Phosphates; D012987:Soil; D014874:Water Pollutants, Chemical; C016213:aluminum oxychloride; D000536:Aluminum Hydroxide; D000535:Aluminum
Coagulation; Nutrient; Plowed soil; Polyaluminum chloride; Recycle; Sludge