Technical feasibility of the use of sludge from the water treatment plant in lettuce production

Abstract

The sludge generated in water treatment plants (WTP sludge), despite having physicochemical characteristics with agricultural potential, is a solid waste discarded in landfills. This research aimed to: 1) evaluate the technical feasibility of WTP sludge in substitution of commercial substrates in the production of lettuce seedlings; 2) to evaluate the yield commercial, in the municipality of Arapiraca, semiarid region of the state of Alagoas - Brazil. The research was carried out in two stages: 1) seedling production in greenhouse in 4 x 4 x 5 factorial arrangement, with four sludge doses (0, 20, 40 and 60%), four commercial substrates (Pindstrup®, Vida Verde®, Bioplant 434® and Bioplant 401®) and five cultivars (Veneranda, Camila, Elba, ‘Vitória Verdinha’ and Diva); 2) seedlings produced at field level were used in 3 x 3 x 5 factorial arrangement, in which Pindstrup treatments and 60% sludge dose were excluded, as they did not promote seedling emergence. In the 1^st experiment, it was observed linear reduction of seedling quality index with the addition of sludge. In the 2^nd experiment, the average yield was 5.4 Mg ha^-1, in which 20% sludge dose promoted the highest values, being recommended for lettuce production in the semiarid region of Alagoas.