Effects of paraffin external coating on the degradable flower pot made of sludge cake

Abstract

Abstract Objectives The researchers have tried to economically make a flower pot from sludge cake produced in paper mill industries for the purpose of decreasing its volume. The crude flower pot did not resist natural sprinkling of water or natural rain. The aims of this study were to clarify two hypotheses: (1) whether life time of a degradable flower pot on the ground would be prolonged or not by coating it with appropriate material, and (2) whether paraffin, material used for coating flower pot, would prevent the toxicity of sludge cake in it. Methods Sludge cake was mixed with soil. The circular plaster mold was used as a fixed mold. Three types of coating materials, paraffin wax, tapioca starch and modified tapioca starch were selected. Water durability test was performed with a water sprinkler. As the toxicological testing, leaching test and seed germination test were used using the paraffin-coated flower pot. Results In the water durability test, the durability was different among types of the coated flower pot. Among them, the paraffin prolonged the life time of flower pot on the ground until 5 weeks at least and may be 8 weeks. The results of leaching test using the paraffin-coated flower pot showed that three heavy metals, lead, nickel and copper, were lower than the standard in Thailand, but the paraffin had no preventive effect on the leaching of the heavy metals from the sludge cake in the flower pot. The seed germination test showed no significant difference in the number of germination of Chinese kale and the length of its leaf from those grown in the plant soil, and suggested that the paraffin-coated flower pot seemed to have no suppressive effect on the seed germination of Chinese kale. Conclusion The paraffin prolongs the life time of flower pot on the ground. Although it has no preventive effect on the toxicity of the sludge cake in the flower pot, the paraffin-coated flower pot seems to have no negative effect on the environment. This paraffin-coated flower pot has the possibility to reuse the sludge cake in the horticultural practice of growing the ornamental plant.