Process design
The typical dimension for a circular clarifier are a re 3 to 5m depth (Ugya & Ajibade, 2016). In this study, the depth is assumed to be 3m. 3m. The suspended solids are settled at the bottom of the clarifier which later being scrap and being pumped to the sludge processing unit. The scum floating to the surface of the wastewater is being skimmed off which later also being pumped to the sludge processing system. At 60% suspended solid removal, the overflow rate is 35m/d (Peavy et al., 1985). From that, the cross-sectional area of clarifier is found f ound to be 252m2. From the area, the diameter is calculated and found to be 17.91m. Assuming the depth as 3m, the volume is 756m 3 and the detention time is 2.06h.
,, = 367. 367.5 5
ℎ
= 8820
Assumption: 60% Suspended solid removal
60% , , % = 35
, =
%
=
8820 / / .
35
.
= 252
4 4 × 2 5 2 / = ( )/ = ( ) = 17.9 17.91 1 Assumption: 3m depth
,, = × ℎ = 252 × 3 = 756 , , =
=
756 8820
Dimension of primary clarifier;
= 0.09 = 2.06ℎ
17.91m
Diameter: 17.91m 3
V:756m
Depth: 756m 3 Volume: 756m 3
m
3
Process description
The primary clarifier is used to remove suspended solid. According to Peavy et al. (1985), the average suspended solid removal for a well operated system is 50 to 60%. In this study, the percent removal of suspended solid is assumed to be 60%. As the suspended solid removed, the BOD of the wastewater also reduce. In other word, the BOD removal is only related to the BOD of the suspended solid removal. At 60% suspended solid removal, the BOD removal percentage is 33% (Peavy et al., 1985). The BOD removal also contribute to t he COD reduction which percentage removal is assumed to be similar to BOD percent removal as explain based on rule of thumb earlier. According to Ugya and Ajibade (2016), the suspended solids such as organic nitrogen, phosphorus and heavy metal are removed from primary clarifier, without removing the dissolved solid. Therefore, the percent removal of ammoniacal nitr ogen also considered as 60% in relation to the 60% suspended solid removal. The color of the wastewater in this study is contributed from the food colouring used and also chicken blood during the process of producing the chicken product, chicken nugget. In many industries, the colour removal are mostly above 90%. For example, 100% colour removal for sanitary landfill leachate (Tatsi et al., 2003) and synthetic reactive dyes (Joo et al ., 2007), 90% for printing and dyeing wastewater (Yue et al., 2008) and 95% for pulp and paper mill wastewater (Irfan et al., 2013). Therefore, the colour removal for this study is assume to be 90%.
Mass balance
Primary clarifier BOD: COD: SS: COL: AN:
Inlet
BOD: COD: SS: COL: AN:
Outlet
Sludge BOD: COD: SS: COL: AN:
Inlet (mg/l) BOD
18,000
Percent removal (%) 33
Outlet (mg/l)
Sludge
100 − 33 100 COD
20,000
100 1,000
100 − 60
1,500
100 200
×=
×=
33 100
×=
×=
60 100
×=
90
100 − 90
Ammoniacal nitrogen
100
60
100 Colour
33
33
100 − 33
Suspended solid
×=
×=
90 100
×=
60
100 − 60 100
×=
60 100
×=
Reference
Irfan, M., Butt, T., Imtiaz, N., Abbas, N., Khan, R. A., & Shafique, A. (2013). The removal of COD, TSS and colour of black liquor by coagulation – flocculation process at optimized pH, settling and dosing rate. Arabian journal of chemistry.
Joo, D. J., Shin, W. S., Choi, J. H., Choi, S. J., Kim, M. C., Han, M. H., ... & Kim, Y. H. ( 2007). Decolorization of reactive dyes using inorganic coagulants and synthetic polymer. Dyes and Pigments, 73(1), 59-64.
Peavy, H. S. R., & Tchobanoglous, D. R. (1985). Environmental engineering . McGraw-Hill Tatsi, A. A., Zouboulis, A. I., Matis, K. A., & Samaras, P. (2003). Coagulation – flocculation pretreatment of sanitary landfill leachates. Chemosphere, 53(7), 737-744.
Ugya, A. Y., & Ajibade, F. O. (2016). Convectional and Advanced Method of Industrial Wastewater Treatment.
Yue, Q. Y., Gao, B. Y., Wang, Y., Zhang, H., Sun, X., Wang, S. G., & Gu, R. R. (2008). Synthesis of polyamine flocculants and their potential use in treating dye wastewater. Journal of Hazardous Materials, 152(1), 221-227.
