MATERIALS & METHODS
To determine the CaCl2
dosage for coagulation of
SDS, CaCl2
solution was added to SDS solution (10,000
mg/L) at concentrations of 0–819 mg/L. After mixing
for a few minutes, the coagulated SDS was removed
by filtration using a 0.45 µm membrane filter and the
chemical oxygen demand (COD) concentration of the
filtrate was measured. The SDS removal ratio was
determined using a COD equivalent of 2.0 (g/g) for
SDS. For determination of CaCl2
dosage for natural
rubber recovery, CaCl2
solution was added to 36,000
mgVS/L of natural rubber latex at concentrations of 0–
3,930 mg/L. After stirring for few minutes, the volatile
solid (VS) concentration was measured to determine
the coagulated rubber quantities.
The DPNR wastewater (Table 1) was collected
from a pilot-scale plant for protein removal at Nagaoka
University of Technology. An optimum dosage of CaCl2
for pre-treatment of DPNR wastewater was
experimentally determined by a coagulation study.
CaCl2
solution was added to the DPNR wastewater at
concentrations of 0–7,710 mg/L and mixed for 1 min.
After agitation, the samples were kept quiescent for 1
h. The SDS and VS concentrations of the supernatant