Abstract
ABSTRACT The sludge produced by rice parboiling wastewater treatment plants has substantial amounts of nutrients and organic matter, therefore requiring proper environmental disposal. One option is to use it as an alternative substrate for the production of forest species seedlings. This study aimed to assess the viability of using the sludge from rice parboiling wastewater as an alternative substrate for the production of Araucaria angustifolia (Bertol.) O. Kuntze seedlings. A. angustifolia seeds were kept in vermiculite until sprouting, then transferred to polyethylene bags filled with five different substrates (treatments): 100% sand (T1); 75% sand and 25% sludge (T2); 50% sand and 50% sludge (T3); 25% sand and 75% sludge (T4); 100% sludge (T5). Each treatment had 10 replicates (bag with one seedling). Shoot system growth, hypocotyl diameter, root system growth and biomass were evaluated at 94, 180, and 300 days of growth. Data were subjected to Analysis of Variance (ANOVA) followed by Tukey test with a significance level of 5%. Seedlings’ growth was similar on treatments containing 25%, 50%, and 75% sludge, while 100% sand and 100% sludge resulted in less growth at 300 days. In conclusion, the sludge from rice parboiling wastewater is suitable as an alternative substrate, and the ratio of 25% sand + 75% sludge could be recommended, for exploit larger amounts of the residue.
Highlights
About 25% of the rice consumed in Brazil comes from parboiling (Paraginski et al, 2014), a process that consists in pre-cooking the grains in potable water aiming to increase their yield and nutritive value (Volpe, 2014)
Considering main shoot height and shoot system total length at 180 days, seedlings grown in sand (T1) had the smallest values (19.73 cm and 29.03 cm, respectively), while treatments with sludge had greater results, no significant difference was observed between them (Table 2)
Data related to the characterization and use of sludge from rice parboiling wastewater treatment plants as alternative substrate for the production of tree species seedlings are scarce in the literature, whereas most of those publications focus on the wastewater treatment system itself but do not mention its sludge disposal
Summary
About 25% of the rice consumed in Brazil comes from parboiling (Paraginski et al, 2014), a process that consists in pre-cooking the grains in potable water aiming to increase their yield and nutritive value (Volpe, 2014). At the end of this process, a sludge waste is generated, whose composition includes organic substances and nutrients such as nitrogen and phosphorus (Faria et al, 2006). There is a growing concern related to the organic and industrial waste disposal, which resulted in research that intends to exploit waste aiming to mitigate the environmental impacts that it could cause if inappropriate disposal occurred (Berilli et al, 2014). The production of seedlings must take into account the substrate, as plants will fix their roots in it and access nutrients and water, influencing the quality of the seedlings (Trigueiro and Guerrini, 2014; Siqueira et al, 2018)
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