Author/Authors :
Mehrdadi، N نويسنده Department of Environment University of Tehran, Tehran, Iran , , Joshi، S.G نويسنده Department of Civil Engineering, I.I.T, Bombay, India , , Nasrabadi، T نويسنده Department of Environment University of Tehran, Tehran, Iran , , Hoveidi، H نويسنده Department of Environment University of Tehran, Tehran, Iran ,
Abstract :
Sludge, which is produced as a by-product of all treatment processes, has
considerable potential as a fertilizer and soil conditioner. Many authorities now discharge the
sludge after treatment directly to agricultural land in liquid form, while some others dewater and
dry it first. In either case, with proper marketing, it is generally possible for an authority to earn
revenue by this means, although it is rare for the income to cover all the cost involved. In some
industrial sludge the total solid concentration may range between 2000-100000 ppm and it is
reported that more than 6000 waste water treatment plants use the conventional sludge drying sand
bed. An experimental investigation was carried out to assess the efficacy of solar energy for drying
of sludge from pharmaceutical industrial waste over a sand bed covered with glass as compared to
the conventional sludge drying over a sand bed as well as to reduce environmental pollution .The
two drying beds are constructed in 12 cm thick brick wall with cement mortar and has an effective
area of 0.5 m 2. On the 0.4 m thick layer of gravel and send the sludge layer from pharmaceutical
industry was deposited. The Solar Sludge Drying Sand Bed (SSDSB) reduced drying time by
about 25-35% as compared to the Conventional Sludge Drying Sand Bend (CSDSB). The rate of
evaporation from the sludge surface and hence the drying was a function of solar radiation. The
condensed evaporated water was qualitatively analyzed for probable reuse.
