Cattail Plant Biomass as a Bulking Agent in Sewage Sludge Composting; Effect of the Compost On Plant Growth

Constructed reed beds or wetlands are low-cost, low technology systems, which are able to treat a variety of wastewaters. This project produced compost from a mixture of sewage sludge and cattail plants (commonly used in constructed wetlands) and studied the effect of the compost on the growth of cattail plants, when it was part of the soil substrates in the beds. To make the compost, cattail plants (Typha domigensis) were collected from a river near the city of Heraklion in Crete, and were shredded and left to dry in the sun. They were then mixed with chopped vine branches in the ratio 5:1 by volume. The mixture was used as a bulking agent with sewage sludge in the ratio 1.5:1 by volume, and composted in a windrow system. The temperatures in the turned piles reached 58°C for about five weeks, without any odour problems. The physicochemical changes in the compost confirmed the effectiveness of the composting process. After six weeks of windrowing and eight weeks of maturation, the compost was used, as a component of soil substrates, in two trials with cattail plants (T. domigensis). The results indicated that the best growth of plants was achieved when the compost was added to a 1:1 volume mixture of clay soil and sand, at the ratio 10 to 15% (v/v).