Study on reuse of heavy metal rich sludge in ceramic pigment and construction material production
In this study, primarily freating waste sludge rich o f Cr, N i, F e,...generated from
electroplating wastewater ừeatment plant and experimentally methods o f utilizing w astes as
inorganic pigment in production o f bricks were carried out. Econom ic, technical and
environmental efficiency and feasibility, bases to apply to practical conditions were evaluated.
The results show that water accounts for about 70% o f sludge. Contents o f N i, Cr and Fe are
relatively high (20, 4.5 and 2.5%, respectively). The wastes could be used to replace inorganic
pigment in brick production after being primarily ừeated with a sim ple procedure. The optimal rate
o f replacing inorganic pigm ent is about 5% and 20% in case o f raw materia! replacement.
The testing results o f technical parameters about com pressibility, flexibility, size...sh o w all tested
products m eeting with standard o f brick brands com m only used in construction. Environmental
safety testing based on heavy metals concentration in rain water soaking tested products (pH value
o f 5.6-5.9) during 2 to 21 days shows the satisfactory in comparison to the permitted standards
(TCVN 5945-2005; Fe< 5, N i< 0.5, and o .lm g /ỉ). Cost-benefit calculations o f utilizing the
wastes reveal that using the wastes to replace inorganic pigm ent in pavement-tiled brick
production gained relatively high econom ic efficien cy and ensure the environmental safety.