Skim natural rubber latex is residual latex obtained as a by-product of concentrating process of natural rubber latex by centrifugation. Skim natural rubber latex contains 3-10% by weight of residual rubber and composes of mainly small rubber particles. In rubber industries, the creaming process to recover this residual rubber commonly used concentrated sulfuric acid which led to an acidic effluent and poor quality of solid rubber. In this study, hydroxypropyl methylcellulose (HPMC) was used instead of concentrated sulfuric acid in creaming process of skim natural rubber latex. The effluents from creaming process both recovered and unrecovered HPMC were examined and compared to the one using concentrated sulfuric acid. As a result, the effluent from creaming process using HPMC was decreased as effluent acidity and sulfate ion were lower than that using concentrated sulfuric acid. Besides, biochemical oxygen demand (BOD) and chemical oxygen demand (COD) value were higher than that using concentrated sulfuric acid. In addition, the hydraulic retention time was affected the pollution of the effluents from creaming process using both recovered and unrecoverd HPMC. Acidity and sulfate ion were decreased as increasing hydraulic retention time. However, BOD and COD value were increased as increasing hydraulic retention time but it may be useful for biogas production in anaerobic treatment of wastewater.