The removal of algal organic matter (AOM) is a growing conc for the water treatment industry worldwide.The current study investigates coagulation of non-proteinaceous AOM (AOM after protein separation),which has been minimally explored compared with proteinaceous fractions.Jar tests with either aluminum sulphate (alum) or polyaluminium chloride (PACl) were performed at doses of 0.2-3.0 mg Al per 1 mg of dissolved organic carbon in the pH range 3.0-10.5.Additionally,non-proteinaceous matter was characterized in terms of charge,molecular weight and carbohydrate content to assess the treatability of its different fractions.Results showed that only up to 25％ of non-proteinaceous AOM can be removed by coagulation under optimized conditions.The optimal coagulation pH (6.6-8.0 for alum and 7.5-9.0 for PACl) and low surface charge of the removed fraction indicated that the prevailing coagulation mechanism was adsorption of non-proteinaceous matter onto aluminum hydroxide precipitates.The lowest residual Al concentrations were achieved in very narrow pH ranges,especially in the case of PACl.High-molecular weight saccharidelike organics were amenable to coagulation compared to low-molecular weight (＜3 kDa) substances.Their high content in non-proteinaceous matter (about 67％) was the reason for its low removal.Comparison with our previous studies implies that proteinaceous and non-proteinaceous matter is coagulated under different conditions due to the employment of diverse coagulation mechanisms.The study suggests that further research should focus on the removal of low-molecular weight AOM,reluctant to coagulate,with other treatment processes to minimize its detrimental effect on water safety.