Impact of sludge and wastewater on Lactuca sativa L. growth and on soil pollution

Two greenhouse pot experiments were conducted in Agrinion, Greece. The impact of treated municipal wastewater (TMWW) and sludge (i) on the growth of Lactuca sativa L. var Longifolia (lettuce) and (ii) on the extent of soil pollution with heavy metals was studied. Soil pollution was assessed by calculating the Pollution Load Index (PLI). Both of these experiments were conducted, using a randomized block design in four replications and seven treatments, respectively, as follows: (a) Experiment A: study of the effect of treated municipal wastewater (TMWW): [Control, 20%, 40%, 60%, 80%, 100%, (100%+30 t/ha Sludge)] and (b) Experiment B: Study of the effect of sludge (t/ha): 0,  6, 12,  18, 24 , 30, (30+100%TMWW). The sludge affected significantly plant height and fresh and dry matter yield, as well as the dry matter N content of plants, while the TMWW affected significantly the dry matter yield and non-significantly the plant height. The pollution load index (PLI) was non-significant for both treatments (sludge and TMWW). According to PLI calibration scale, the soil was found to be slightly polluted with heavy metals under both treatments.