The distribution of inherent phosphorus in fifteen water treatment residues from South Africa

Abstract

Water treatment residues (WTR), the by-products of the production of potable water, are chemically benign, inorganic materials which are suitable for disposal by land application, though they are frequently reported to have high phosphorus (P) sorption capacities. An understanding of the distribution of inherent P in WTR is, however, required, if sorption-desorption processes are to be correctly interpreted. The aim of this investigation was to characterise the chemical properties relevant to P-sorption/desorption processes of 15 South African WTR and to determine the inherent distribution of P within the WTR using a chemical fractionation procedure. The pH, exchangeable Ca and organic carbon content ranged from 4.77 to 8.37, 238 to 8 980 mg·kg -1 and 0.50 to 11.6 g·100 g , respectively. Mechanisms of P-retention are residue specific, being dependent on the chemical properties of the WTR. Elevated Ca and amorphous Al and Fe concentrations did, nevertheless, suggest that all residues had the capacity to adsorb high amounts of P and to retain this P in forms unavailable for plant uptake.

Correlation of Phosphorus Adsorption with Chemical Properties of Aluminum-Based Drinking Water Treatment Residuals Collected from Various Parts of the United States

“…The pH values ranged from slightly acidic (6.03) to alkaline (9.78); however, the majority of the samples had near-neutral pH, with an average of 7.4. The observed range was similar to findings for WTRs reported in many other studies and geographic locations such as China [ 39 ], the US [ 18 , 31 , 40 ], and South Africa [ 41 ], possibly because alum coagulation is recommended when the source water has a pH of 5 to 7. Samples with higher pH values, such as those from South Dakota, have a high acid-neutralizing capacity and might be useful for resolution of the issue of acidic soils [ 18 ].…”

“…Oxalate-extractable Al (Alox) and Fe (Feox) are important chemical properties of WTRs, representing chemical proxies for amorphous Al and Fe oxide/hydroxide surfaces, respectively, that are available for the adsorption of metals and oxyanions [ 42 , 43 ] and have been reported to vary widely from 1 to 160 mg/g in various studies conducted on WTRs collected from various locations [ 4 , 8 , 39 , 40 , 41 ]. In the current study, Alox ranged from 0.27 to 166.54 mg/g, and Feox ranged from 0.48 to 22.2 mg/g ( Figure 1 ).…”

“…The phosphorus saturation index (PSI) is a parameter that determines whether reactive Al and Fe surfaces in a solid are saturated with P (PSI > 100%) or whether they are still capable of adsorbing more P (PSI < 100%) [ 41 ]. None of the samples were saturated with P ( Table 1 ); however, samples from South Dakota and Nebraska were expected to have lower adsorption capacities, as their PSI was higher than that of other WTRs.…”

Better Together: Water Treatment Residual and Poor‐Quality Compost Improves Sandy Soil Fertility

“…The implications of land application have been well researched (Ippolito et al, 2011). A major limitation encountered with land application of WTR is the high phosphorus (P)‐fixation capacity of the iron (Fe) and aluminum (Al) oxyhydroxides (Elliott and Dempsey, 1991; Ippolito et al, 2003; Norris and Titshall, 2012). The addition of WTR to soils results in yield loss and P‐deficiency symptoms in maize ( Zea mays L.) (Rengasamy et al, 1980), lettuce ( Lactuca sativa L.) (Elliott and Singer, 1988) and sorghum [ Sorghum bicolor (L.) Moench]–sudangrass [ S. bicolor ssp.…”

Waste to resource: use of water treatment residual for increased maize productivity and micronutrient content

“…Although WTRs are typically low in P (Dassayanake et al 2015), compost addition provided readily available P (due to its higher content of available P as shown in Table 1), whilst WTR provided N and a favourable pH for nutrient uptake. Land application of WTR for plant production is often constrained due to potential adsorption of P by the Al and Fe oxides normally present in WTR, making P unavailable for plant uptake (Babatunde et al, 2008;Bai et al, 2014;Norris & Titshall, 2012). The similarity in maize dry matter yield between 10% Al-WTR ?…”