口 Inorganic Ace.68.8% D Organic Ace. 31.2% 4567891012131415161718192021 Sample number Fig 5 Inorganic and organic fractions of total nitrogen in the raw sewag Dissolved 045pm Organic D-O Fig. 6 Classification of pollutants by a 2 x 2 water quality matrix 4 Treatability evaluation of contaminants in ecause a 0. 45-um filter was used for the classification domestic sewage of suspended and dissolved substances, the existence of upended solid particles in the raw sewage might have much 4. 1 Formulation of a water quality matrix influenced the fractions of BOD, cod, TP, and TN, as shown in Fig. 6. if we consider that even dissolved substances might Based on the results mentioned above, a water quality matrix be attached to the surface of the suspended particles [9] was formulated as shown in Fig. 6. The figure is a 2 x2 Therefore, Fig. 6 might not represent the real state of the matrix and can thus classify each of the contaminants into individual substance existing in the sewage. However, from the viewpoint of treatment, such a water quality matrix 4 groups, namely dissolved-organic(D-O), suspended-organ- was still useful to assist the selection of suitable wastewater ic(S-O), dissolved-inorganic(D-I)and suspended-inorganic (S-I)substances. The differences of organic SS. COD and treatment processes total phosphorus(TP) from inorganic ones were conducted principally by ignition method 4.2 Treatability of contaminants of suspended and As shown in Fig. 6, in the raw sewage investigated, dissolved fractions SS included both organic and inorganic fractions at about 45% and 55%, respectively. BOD, represented biodegradable Table 2 compares the removals of the total, suspended, and organics of which 62% belonged to the suspended fraction dissolved fractions by the primary, enhanced primary, and and of which the remaining 38% belonged to the dissolved secondary treatment processes based on this study. By the fraction. COD was composed of both organic substances and primary treatment experiment, i.e., plain sedimentation, reductive inorganic substances that consumed oxygen. The the average removal of Ss was 59.8%. Regarding COD percentages of the suspended and dissolved fractions of Cod and BODs, the overall removals were 39.6% and 38.9%, were 66% and 34%, respectively, which are very similar to respectively, and all the removed contaminants were found that of BODs. Regarding TP, about 60% was inorganic, and to belong to the suspended fraction. Considering that the its suspended and dissolved fractions were almost equal Of suspended COD and BODs were about 66% and 62%, the TN, the inorganic and dissolved fraction took most parts. respectively, as shown in Fig. 6, the removal percentages60 4 Treatability evaluation of contaminants in domestic sewage 4.1 Formulation of a water quality matrix Based on the results mentioned above, a water quality matrix was formulated as shown in Fig. 6. The figure is a 2x2 matrix and can thus classify each of the contaminants into 4 groups, namely dissolved-organic (D-O), suspended-organ￾ic (S-O), dissolved-inorganic (D-I) and suspended-inorganic (S-I) substances. The differences of organic SS, COD, and total phosphorus (TP) from inorganic ones were conducted principally by ignition method. As shown in Fig. 6, in the raw sewage investigated, SS included both organic and inorganic fractions at about 45% and 55%, respectively. BOD5 represented biodegradable organics of which 62% belonged to the suspended fraction and of which the remaining 38% belonged to the dissolved fraction. COD was composed of both organic substances and reductive inorganic substances that consumed oxygen. The percentages of the suspended and dissolved fractions of COD were 66% and 34%, respectively, which are very similar to that of BOD5. Regarding TP, about 60% was inorganic, and its suspended and dissolved fractions were almost equal. Of the TN, the inorganic and dissolved fraction took most parts. Because a 0.45-μm filter was used for the classification of suspended and dissolved substances, the existence of suspended solid particles in the raw sewage might have much influenced the fractions of BOD5, COD, TP, and TN, as shown in Fig. 6, if we consider that even dissolved substances might be attached to the surface of the suspended particles [9]. Therefore, Fig. 6 might not represent the real state of the individual substance existing in the sewage. However, from the viewpoint of treatment, such a water quality matrix was still useful to assist the selection of suitable wastewater treatment processes. 4.2 Treatability of contaminants of suspended and dissolved fractions Table 2 compares the removals of the total, suspended, and dissolved fractions by the primary, enhanced primary, and secondary treatment processes based on this study. By the primary treatment experiment, i.e., plain sedimentation, the average removal of SS was 59.8%. Regarding COD and BOD5, the overall removals were 39.6% and 38.9%, res pectively, and all the removed contaminants were found to belong to the suspended fraction. Considering that the suspended COD and BOD5 were about 66% and 62%, respectively, as shown in Fig. 6, the removal percentages Fig. 5 Inorganic and organic fractions of total nitrogen in the raw sewage Fig. 6 Classification of pollutants by a 2x2 water quality matrix