Assessment of Phytotoxicity of Potable Water Treatment Plant Sludge-bound Compost Pellets on Seed Germination of Radish (Raphanus sativus L.)

Proceedings of International Forestry and Environment Symposium Pub Date : 2024-02-15 DOI:10.31357/fesympo.v27.6615

De Silva R.S.D., Amarasinghe S.R., Ranawaka R.A.A.K.

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Abstract

Binding loose compost into pellets needs different binding materials. Maintenance of pellet stability highly depends on the binding materials used. Potable water treatment plant sludge (WTPS) has the potential to be used as a binding material due to the high content of clay, organic matter, and nutrients. However, compost and WTPS may contain heavy metals, toxic compounds, salts, and growth inhibitors. Therefore, the determination of the phytotoxicity of WTPS bound compost pellets is essential before amending them to the soil. The present study aimed to assess the phytotoxicity of different pelleted compost using seed germination bioassay of Raphanus sativus L. Four compost pellets were considered (T1: commercial compost pellet (100% compost), T2: commercial integrated pellet (90% compost+10% inorganic fertilizer), T3: WTPS-bound compost pellet (90% compost+10% WTPS), T4: WTPS-bound integrated pellet (80% compost+10% WTPS+10% inorganic fertilizer)) and pellet aqueous extracts (PAE) were prepared, respectively. Distilled water was used as the control. The dilution sequence of PAE as 50% and 100% were tested for seed germination in Petri dishes in a randomized design with three replicates. pH, EC, and selected heavy metals (Al, Zn, Cu and Cr) were determined in PAE. RSG% (Relative Seed Germination %), RRG% (Relative radicle Growth %), and GI% (Germination Index) were calculated for all the PAE after 72 hours. The PAE had a pH range from 6.8-7.2. The Cr was not detected in all 100% PEA. The highest levels of Al and Zn were detected in 100% PAE of T1. All the treatments in both 50% and 100% PAE showed GI% higher than 80% except the 100% PAE of commercial integrated pellet (T2) and WTPS-bound integrated pellet (T4). The PAE from the T2 and T4 showed low RSG% and RRG% and thereby the GI% is low due to high EC in PAE. The GI% of 100% PAE in T2 and T4 was 32.33% and 67.25%, respectively. The lowest values for RSG% and RRG% were recorded for T2 as 44.44% and 72.75%, respectively. Spearman‘s Rank Correlation coefficients were calculated for EC with RSG%, RRG%, and GI% and all variables showed negative correlations as (-0.44), (-0.97), and (-0.69), respectively. This indicates that high EC reduces radical growth and seed germination. PAE at 100% concentration levels of commercial integrated pellet showed high phytotoxicity, and WTPS-bound integrated pellet showed less phytotoxicity while other treatments did not show any sign of phytotoxicity. All the PAE at 50% concentration level were free from phytotoxicity. Hence, 10% WTPS in w/w basis can be used as a binding agent in pelletizing loose compost. Different WTPS concentrations should be tested in binding process for its optimum utilization. Keywords: Bioassay, Compost, Phytotoxicity, Radish, Water treatment plant sludge

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饮用水处理厂污泥堆肥颗粒对萝卜种子发芽的植物毒性评估

将松散堆肥粘合成颗粒需要不同的粘合材料。颗粒稳定性的保持在很大程度上取决于所使用的粘合材料。饮用水处理厂污泥（WTPS）由于含有大量粘土、有机物和营养物质，有可能被用作粘合材料。不过，堆肥和 WTPS 可能含有重金属、有毒化合物、盐类和生长抑制剂。因此，在将 WTPS 复合堆肥颗粒添加到土壤中之前，必须确定其植物毒性。本研究旨在利用菜籽萌芽生物测定法评估不同颗粒堆肥的植物毒性。本研究考虑了四种堆肥颗粒（T1：商业堆肥颗粒（100% 堆肥）；T2：商业综合颗粒（90% 堆肥+10% 无机肥）；T3：WTPS 结合堆肥颗粒（100% 堆肥）；T4：WTPS 结合堆肥颗粒（90% 堆肥+10% 无机肥）；T5：WTPS 结合堆肥颗粒（90% 堆肥+10% 无机肥）；T6：WTPS 结合堆肥颗粒（90% 堆肥+10% 无机肥）：结合 WTPS 的堆肥颗粒（90% 堆肥+10% WTPS），T4：分别制备了 WTPS 结合堆肥颗粒（80% 堆肥+10% WTPS+10% 无机肥）和颗粒水提取物（PAE）。蒸馏水用作对照。将 PAE 稀释为 50%和 100%，在培养皿中进行种子萌发试验，采用随机设计，三次重复，测定 PAE 中的 pH 值、EC 值和选定的重金属（Al、Zn、Cu 和 Cr）。72 小时后，计算所有 PAE 的 RSG%（相对种子发芽率）、RRG%（相对胚根生长率）和 GI%（发芽指数）。PAE 的 pH 值范围为 6.8-7.2。在所有 100% 的 PEA 中均未检测到铬。在 T1 的 100% 泛酸中检测到的铝和锌含量最高。除了 100%PAE的商业综合颗粒（T2）和 WTPS 结合的综合颗粒（T4）外，50%和 100%PAE的所有处理的 GI% 都高于 80%。T2 和 T4 的 PAE 显示出较低的 RSG% 和 RRG%，因此，由于 PAE 中的高导电率，GI% 较低。在 T2 和 T4 中，100% PAE 的 GI% 分别为 32.33% 和 67.25%。T2 的 RSG% 和 RRG% 值最低，分别为 44.44% 和 72.75%。计算了 EC 与 RSG%、RRG% 和 GI% 的斯皮尔曼等级相关系数，所有变量均呈负相关，分别为 (-0.44)、(-0.97) 和 (-0.69)。这表明，高浓度的氨基甲酸乙酯会降低自由基的生长和种子的萌发。在 100%浓度水平的 PAE 处理中，商品综合丸剂显示出较高的植物毒性，WTPS 结合的综合丸剂显示出较低的植物毒性，而其他处理未显示出任何植物毒性。所有 PAE（浓度为 50%）都没有植物毒性。因此，10% WTPS（重量比）可用作松散堆肥造粒的结合剂。应在粘合过程中测试不同浓度的 WTPS，以优化其利用率。关键词生物测定堆肥植物毒性萝卜水处理厂污泥

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Proceedings of International Forestry and Environment Symposium

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