Utilization of Paint Industry Sludge for Culturing Earthworms.

Sludge generated from water treatment plant in two different paint and pigment manufacturing industries were used for culturing earthworms (Eisenia foetida Savigny) and possibility of getting a quality vermicompost was also explored. The sludges were collected from the sludge drying beds of two industries, one manufacturing CPC Green (Copper pthalocyanine green) and the other manufacturing acrylic (pure and styrene) washable distempers, synthetic enamels, fillers and putties. The sludges were used pure and mixed with rotten and a month old cowdung at 1:1, 1:2, 1:3, 2:1 and 3:1 ratios (sludge: cowdung). In pure sludges and in 3:1 ratio earthworms did not survive. Sludges were alkaline, non-saline, but had appreciable Ca, Al, Pb, Zn, Mn while CPC green particularly had high Cu (12930 mg kg^-1) and the other had high total Cr (156 mg kg^-1). High Ca and Al in both came from water treatment chemicals lime and alum while CPC green itself is a copper based pigment. The sludges were suitable for land application as regard to their metal contents except for Cu in CPC green. CPC green did not support proper growth of plants (green gram, Vigna radiata (L). R. Wilcz.) while the acrylic paint sludge supported growth in pure form and mixtures with soil. Earthworms had very low survival in CPC green sludge and its mixtures although mixtures were microbially active and the acrylic paint sludge was very efficient in supporting worm growth and worm castings were generated in quick time. Castings were nutritionally acceptable but the original colour of the raw materials remained unchanged in the castings indicating no conversion of the paint/pigments. [ABSTRACT FROM AUTHOR]