Page 96 - Industrial Wastewater Treatment, Recycling and Reuse

Industrial Wastewater Treatment, Recycling, and Reuse: An Overview 71

overall economic benefits can be very high for industry as well as for soci-
ety. Industries that have wastewater suitable for such purposes can ally with
local corporation bodies for the treatment, recycling, and reuse necessary
and come up with designs for appropriate distribution of fresh and recycled
water. Typical concentrations of elements in treated wastewater effluent
from conventional sewage treatment processes are 50 mg/L of nitrogen,
10 mg/L of phosphorus, and 30 mg/L of potassium. Assuming an appli-
3
cation rate of 5000 m /ha/year, the fertilizer contribution of this effluent
would be 250 kg/ha/year of nitrogen, 50 kg/ha/year of phosphorus, and
150 kg/ha/year of potassium. Thus, the effluent would supply all of the
nitrogen and much of the phosphorus and potassium normally required
for agricultural crop production. Other valuable micronutrients and the
organic matter contained in the effluent would also provide benefits
(Corcoran et al., 2010). Recently, CPCB India attempted to evaluate
the value associated with municipal wastewaters with the assumption that
both water and nutrients have value and that there is no loss of nutrients
during treatment. It found that the fertilizer equivalent along with waste-
water worth Rs 1091.20 million are discharged in to the coastal waters
from coastal cities and towns annually (CPCB, 2009–10b; http://nptel.
iitm.ac.in/courses/105105048/M11_L14.pdf). This one example should
be an eye opener for both environmental bodies and industries and clearly
highlights the importance of water recycling and reuse in an appropriate
manner. A recent report by IWMI (Amerasinghe et al. 2013) also high-
lights value additions due to domestic wastewater treatment, while cau-
tioning about adverse effects of wastewater usage in irrigation. It is to
be emphasized that the adverse effects can be practically eliminated if
the wastewaters are accurately characterized as discussed in the earlier sec-
tions and suitably treated (for augmentation of N, P, and K as well as for
removal of heavy metals and other harmful pollutants) before considering
its use for agricultural purposes.
2. Process modifications can substantially reduce the cost of wastewater
treatment apart from a change of methodology for effluent treatment,
land/space requirements, equipment costs, and legal binding legislation
concerning pollution levels. Such changes are far better than end-of-pipe
solutions in the form of stringent methods of treatment, such as oxida-
tion, that are highly energy intensive. Use of easily biodegradable raw
materials, fewer refractory pollutants generated for simpler treatments,
and easy recycling and reuse can be potentially attractive options from
a cost-consideration point of view.