THE EFFECT VARIATION OF DETENTION TIME IN ROTATING BIOLOGICAL
CONTACTORS (RBCs) PROCESSING UNIT WITH PVC MEDIA TO DECREASE CONCENTRATION OF
PHOSPHATE IN LAUNDRY WASTEWATER
Laundry wastewater contains
high concentration of phosphate but people discharge directly to river without
processing it before. Some Communal Waste Water Treatment Plant (WWTP) do not
receive laundry wastewater. The results of laboratory test showed that concentration
of phosphate in laundry wastewater was 20,48 mg/l. Thus, it can cause
environmental pollution, such as eutrophication. The research goal is to know the effect variation of detention
time 24, 48, and 72 hours in Rotating Biological Contactors (RBCs) processing
unit with PVC media to decrease concentration of phosphate in laundry
wastewater. This research type is experiment with pre test-post test design.The
object of this research is laundry wastewater Eng in Tembalang, Semarang. The
technical laboratory test of sample is using Vanadatmolybdate method and the
data analysis use One Way Anova test then it is continued with Post Hoc Test.
The result shows that average of phosphate concentration before processing is
18,73 mg/l, where is after processing within 24 hours is 7,25 mg/l, within 48
hours is 7,07 mg/l, and within 72 hours is 3,61 mg/l. Decreasing phosphate concentration
of laundry wastewater within 24 hours is 61,12%, within 48 hours is 62,07, and
within 72 hours is 80,51%. Statistical result by One Way Anova showed that
there is average difference from decreasing phosphate concentration in laundry
wastewater (p-value=0,002). It is suggested to use 72 hours detention time to
decrease concentration of phosphate as the decreasing effect is highest than
others, althought hasn’t fulfill the regulation.
