Experimental investigation of interactions between the temperature field and biofouling in a synthetic treated sewage stream

Abstract

Biofouling causes significant losses in efficiency in heat exchangers recovering waste heat from treated sewage. The influence of the temperature field on biofouling was investigated using a flat plate heat exchanger which simulated the channels in a plate and frame unit. The test surface was a 316 stainless steel plate, and a solution of Bacillus sp. and Aeromonas sp. was used as a model process liquid. The test cell was operated under co-current, counter-current, and constant wall temperature configurations, which gave different temperature distributions. Biofouling was monitored via changes in heat transfer and biofilm thickness. The effect of uniform temperature on biofouling formation was similar to the effect of uniform temperature on planktonic growth of the organisms. Further results showed that the temperature field, and particularly the wall temperature, influenced the rate of biofouling strongly. The importance of wall temperature suggests that fouling could be mitigated by using different configurations in summer and winter.

Using Thermal Shock to Inhibit Biofilm Formation in the Treated Sewage Source Heat Pump Systems

“…Previous studies [11,41] have shown that the thermal resistance of the biofilms were linearly correlated with the biofilm thickness and the wet weight. In this study, the thermal resistance is of the main interest and the wet weight of the biofilms, instead of the cell count or the dry biomass, was measured.…”

“…A previous study [41] has shown that the dominant bacteria of the treated sewage in six Beijing sewage plants was Bacillus sp. (>62%).…”

“…where T m,out , T m,in , T c,out , T c,in were the outlet and inlet temperatures of the model sewage and the clean water ( • C), Q v,m , and Q v,c were the flow rate of the model sewage and the clean water (m 3 /s), ρ was the water density (996 kg/m 3 ), c p was specific heat at constant pressure of water (4.18 × 10 3 J/(kg·K)) and A was the equivalent heat transfer area of the heat exchanger (m 2 ) [41,43].…”

A New Approach for Mitigating Biofouling by Promoting Online Cleaning Using a Sacrificial Paraffin Coating

“…(gram-positive) and Aeromonas sp. (gram-negative) accounted for more than 80% of the biomass in suspension and 95% of the organisms forming biofilms [23].…”

Choosing When to Clean and How to Clean Biofilms in Heat Exchangers

“…It considers the problem where three or more methods are avail-able, building on the characteristic behavior observed in many cases of biofouling illustrated in the fouling resistance-time (Rf-t) data [12] in Figure 1. The three phases of fouling growth reported by reference 1 are evident:…”