Alum application to improve water quality in a municipal wastewater treatment wetland: Effects on macrophyte growth and nutrient uptake

Abstract

Application of low doses of alum to treatment wetlands to reduce elevated outflow winter phosphorus concentrations were tested in mesocosms vegetated with either Typhadomingensis, Schoenoplectus californicus, or submerged aquatic vegetation (SAV) (Najas guadalupensis-dominated). Alum was pumped to experimental units at a rate of 0.91 g Al m(-2) d(-1) and water quality monitored for 3 months. The alum application significantly improved the outflow water quality and overall the growth of the plants was unaffected by the alum application. Biomass and growth varied between species and through time, but no significant effects of alum application were detected. The concentrations of nutrients and mineral elements in the aboveground tissues differed between species and over time, but only the concentration of Al in plant tissue was increased by alum additions. The concentration of Al was 50-fold higher in alum-treated SAV as compared to the control, and in Typha and Schoenoplectus the concentrations were 4- and 2-fold, higher, respectively. The N/P ratios in the plant tissues were low (<10) suggesting that their growth and biomass was limited by nitrogen. The research suggests that a continuous or seasonal low-dosage alum application to treatment wetlands provides an effective tool to maintain discharge concentrations within permitted values during the inefficient winter treatment times. We suggest that the use of alum should be restricted to treatment wetland areas dominated by emergent vegetation as the effects of the elevated Al concentrations in SAV needs further study.

Impacts of residual aluminum from aluminate flocculant on the morphological and physiological characteristics of Vallisneria natans and Hydrilla verticillata

“…Al may have harmful effects on the chlorophyll fluorescence parameters and metabolic enzymes in plants (Wang et al, 2010), where they may be susceptible to the loss of magnesium from the porphyrin ring of the chlorophyll molecule when encountering Al, and the degree of damage is positively correlated with the Al concentration (Zhang and Zhou, 2005). In addition, the physicochemical reactions with Al in water can severely affect the biogeochemical cycling of other elements and the migration of other pollutants (Malecki-Brown et al, 2010;Vicente et al, 2008). Very high levels of residual Al can inhibit the formation of mycorrhiza to interfere with the absorption and transport of Ca, P, and Mg in plants (Baligar et al, 1987), where P and Mg are highly important for chlorophyll synthesis.…”

“…The negative associations between biomass and plant height with the Al contents of the water and sediments in the in situ experiment strongly suggest that the aluminate flocculant significantly degraded the morphological characteristics (P < 0.05), as also shown by Ji et al (2013) and Ahmad et al (2013). Furthermore, Al can limit plant growth by affecting asexual reproduction (Malecki-Brown et al, 2010). The roots are generally considered to be the target organ of Al toxicity (Robert and Richard, 1999;Barcelo and Poschenrieder, 2002), where Al ions are absorbed mainly on the root tips and parts of the lateral roots where cell divide vigorously, thereby severely hindering root cell division and elongation (Barcelo and Poschenrieder, 2002).…”

“…Many previous studies have investigated the effects of Al on terrestrial plants (Delhaize and Ryan, 1995;Zhang and Zhou, 2005), particularly crops (Ma and Yang, 2011;Kochian et al, 2004), but the influence of Al phytotoxicity on submerged macrophytes still remains poorly understood. Al toxicity is commonly considered to be an abiotic stress factor that limits plant growth by altering physiological, molecular, and cellular functions (Malecki-Brown et al, 2010;Amenos et al, 2009) by interfering with the absorption and transport of mineral nutrients (Vicente et al, 2008) such as Ca and Mg (Baligar et al, 1987), as well as by affecting the behavior of many key enzymes (Tewari et al, 2004). Al toxicity is strongly associated with the activity of Al 3+ (Malecki-Brown et al, 2010), pH, and the Al concentration (Djouina et al, 2016).…”

“…Al toxicity is commonly considered to be an abiotic stress factor that limits plant growth by altering physiological, molecular, and cellular functions (Malecki-Brown et al, 2010;Amenos et al, 2009) by interfering with the absorption and transport of mineral nutrients (Vicente et al, 2008) such as Ca and Mg (Baligar et al, 1987), as well as by affecting the behavior of many key enzymes (Tewari et al, 2004). Al toxicity is strongly associated with the activity of Al 3+ (Malecki-Brown et al, 2010), pH, and the Al concentration (Djouina et al, 2016). Root uptake is the dominant route for Al entry into terrestrial plants, and thus inhibition of root elongation and respiration are likely targets for Al toxicity (Barcelo and Poschenrieder, 2002;Catallo et al, 1993), thereby resulting in thickened, stubby, and brittle roots.…”

Influence of alum on cyanobacterial blooms and water quality of earthen fish ponds

“…Barkoh et al (2013) suggested that alum may be useful for controlling pH in striped bass production ponds where the inorganic fertilization treatment is applied with inhibition of phytoplanktonic growth as a result of phosphate precipitation. Starting around 1980, it became widely accepted that alum was a major factor used for successful treatment in lake restoration and, consequently, success of aquatic organisms and communities to grow in their habitats (Soltero et al 1981;Malecki-Brown et al 2010). Alum is acidic in water and can reduce total alkalinity by neutralizing carbonate and bicarbonate compounds, with greater efficiency in reducing pH when applied to water with low initial total alkalinity (Barkoh et al 2013).…”