**8. Fouling mitigation by green technology (catalytic mitigation and green additive)**

Physical water treatment (PWT) is a good alternative for safe and efficient nonchemical fouling mitigation method. Examples of PWT include permanent magnets [32], solenoid coil devices [33], green additive [34] and catalytic materials and alloys [35].

To mitigate scaling on heat transfer surfaces, chemical additives are often used, but chemicals are expensive and pose hazard threat to the environment and health. Mitigation of calcium sulphate dehydrates scale formation on heat exchanger surfaces by using natural wood pulp fibre was conducted by Kazi [36] and others in University of Malaya. Experimental work was designed and fabricated to study the use of natural wood pulp fibre as a means of fouling mitigation as seen in **Table 2** and **Figure 6**.


**Table 2.** Experiments set-up for fouling mitigation by incorporating green additives [36][37].

**Figure 6.** Schematic diagram of experiemental flow loop [37][36].

**Figure 7.** Fouling resistance as a function of time for eucalyptus fibre in the supersaturated calcium sulphate solution [38][37].

**Figure 7** depicts the fouling resistance as a function of time for calcium sulphate solution with different fibre concentration of 0.25% (1), 0.15% (2), 0.05% (3) and 0.02% curve (4) in the mineral solution. Results show that the fibres in solution retarded fouling on heated surfaces and the retardation is proportional to the concentration of fibre in the solution. The induction period has also increased.
