Adaptation of the CAS test system and synthetic sewage for biological nutrient removal - Part I: Development of a new synthetic sewage

A new synthetic medium has been developed for routine use in laboratory-sca le sewage treatment simulation and biodegradation tests, such as OECD guide line 302A & 303A [1] or ISO method 11733 [2]. The new medium, Syntho, was d esigned to meet the following objectives: 1) to be more representative of r eal sewage than the existing standard OECD synthetic sewage, 2) the COD:N:P ratio and mineral composition must allow a good degree of biological nutri ent (N, P) removal, and 3) the medium should result in stable unit operatio n, including good sludge settling and minimal need for control actions. The IAWQ Activated Sludge Model No. 2 (ASM2, [3]) was used to help design the medium and predict reactor performance for different possible media composi tions. The results obtained with Syntho indicate that Continuous Activated Sludge (CAS) units with or without nutrient removal can be operated routine ly on this feed. The new medium was also characterized by means of a respir ation test. The different influent fractions applied in the model were vali dated, and a respiration profile indicated that Syntho is a close approxima tion of real sewage. (C) 1998 Elsevier Science Ltd. All rights reserved.