During the operation of the circulating cooling water system, inorganic scale deposition may cause technical problems, such as reduction of heat transfer efficiency in cooling systems and obstruction of pipes. In the industry, chemicals are often used as scale inhibitors in scale deposition control, antiscalants popular in industry are generally phosphorus and nitrogen-containing chemicals, which may lead to eutrophication. However, increasing environmental concern and discharge limitations have guided antiscalants to move toward biodegradability, nontoxicity and cost–effectiveness. This paper reviews current research on the application of using bio-materials as scale inhibitors, including proteins and amino acids, polysaccharides, plant extracts, microbial reagents, and microbiological products. The non-bioaccumulation, low cost, readily biodegradability and sustainably available characters promote the development of green-scale inhibitor chemistry.

A biological method was developed for reusing urban reclaimed water in circulating cooling water system (CCWS), in which the compound microorganism preparation (CMP) mainly including nitrobacteria, bacillus subtilis, photosynthetic bacteria and thiobacillus denitrificans was used to control the scaling, corrosion and biofouling of CCWS. The abundant carbon, nitrogen and phosphorus elements in urban reclaimed water met the needs of microbial growth. Compared with chemical agent, CMP had the advantages of high efficiency, no additional medical and more economical. The research results showed that CMP improved water quality and decreased ammonia nitrogen (NH₃-N) and chemical oxygen demand (COD). The concentration ratio of CCWS reached 3.87 by using CMP. The corrosion inhibition rate of CMP and the removal rate on biofouling achieved 99.69% and 22.21%, respectively. Moreover, the mechanisms of CMP controlling scaling, corrosion and biofouling were discussed. And the surface characteristics and chemical compositions of corrosion products and biofouling were analyzed.

Metamaterials have shown great potential for controlling acoustic waves and structural dynamics. Although various types of metamaterials have been developed, simultaneous control of low-frequency sound in air and vibration in solids is less investigated. This paper presents hybrid acousto-elastic metamaterials that enable simultaneous control of low-frequency sound in air and vibration in solids. For the first time, this novel metamaterial adds a compound of membrane and silicone rubber to cladding. The membrane moves the resonance frequency to a low frequency, and the silicone rubber makes the cladding layer rigid enough to support the mass. Bandgap, sound transmission loss (STL), and vibration transmission loss (VTL) were calculated by using the finite element method. Combining modal vibration mode and sound intensity streamline, the mechanisms of vibration isolation and noise reduction were analyzed and then verified through the equivalent mass–spring model. This novel metamaterial combines acoustic metamaterials and mechanical metamaterials to achieve the collaborative control of elastic waves and acoustic waves. At the same time, the peak frequencies of both STL and VTL are lower than those of the traditional metamaterials of the same size, which provides a theoretical basis and method guidance for the next step of collaborative control research of mechanical metamaterials and acoustic metamaterials. It has potential application value in the field of low-frequency vibration and noise control engineering.