Can Desalination and Clean Energy Combined Help to Alleviate Global Water Scarcity?

The major present hindrance in using desalination to help alleviate global water scarcity is the cost of this technology, which, in turn is due to energy cost involved. This study examines historical trends in desalination and breaks up the cost of desalination into energy based and nonenergy based. It then develops the learning curves (relationship between cumulative production and market price) for desalination. Assuming that the photovoltaic (PV) technology will be the dominant form of energy used in the desalination process, the existing PV learning curve and desalination learning curve are combined to explore the viability of large‐scale adoption of desalination in the future. The world has been divided into seven regions and it is assumed that water demand from desalinated water will be met only within the 100‐km coastal belt. It is shown that, in most of the regions, other than sub‐Saharan Africa, Central America, and South Asia (where water tariffs are low), the desalination (without considering energy) becomes viable by 2040. For PV technology, less than 1 million MW per annum growth is required till 2050 to make it affordable. Globally, desalination with renewable energy can become a viable option to replace domestic and industrial water demand in the 100‐km coastal belt by 2050.     

Enhancing Diatom Growth by Using Zeolites to Change Seawater Composition (4 pp)

- Aims and Scope. The purpose of this study was to test whether two zeolites produced synthetically (products of zeolitic nature, PZN) could influence either the yield of a diatom culture or the chemical changes in the cultures. For this purpose, Phaeodactylum tricornutum was used as test organism in a culture medium of natural seawater enriched with N and P having negligible amounts of ammonia. Methods The PZN ZEBEN-06 and ZESTEC-56 were used in parallel experiments. The composition of trace metals and organic compounds with chelate activity in the culture media, were determined by anodic or cathodic stripping voltammetry. The impact of leaching silicon on the algal yield was evaluated by comparing the growth in the presence or absence of PZN, in seawater enriched or not-enriched with silicon. Results and Conclusions Both PZN significantly promoted the algal yield even in the absence of added silicon, a limiting nutrient for diatom growth. The PZN acted as a silicon buffer while providing a source of silicon required for growth. In addition, PZN released into the seawater small but significant amounts of the limiting micro-nutrient manganese (its concentration doubled during the experiments), while simultaneously removing relatively high quantities of zinc from the seawater. The presence of PZN inhibited the releasing of chelated compounds. These changes (sorption/desorption) caused by the PZN in the concentrations in the solutions used as culture media of P. tricornutum were probably responsible for the differences in both the diatom and exudation observed in the tested cultures.     

高锰酸钾凝胶缓释剂的制备及其缓释去除水中三氯乙烯

本研究开发一种结合原位化学氧化和二氧化硅溶胶-凝胶的可控氧化剂释放技术，制备出一种高锰酸钾（KMnO₄）凝胶缓释剂（SRPG）.优化SPRG的制备条件和探究影响其在水中缓释效率的因素，并考察其对不同氯代烃的降解效果.结果表明：二氧化硅溶胶的质量分数、KMnO₄的含量及pH对SRPG凝胶化过程有显著的影响；提高缓释剂中KMnO₄的含量和降低二氧化硅溶胶质量分数，可有效提高SRPG中KMnO₄的释放速率，当KMnO₄质量分数为6.51‰，二氧化硅溶胶质量分数为40%，KMnO₄的释放符合拟一阶动力学，释放速率kobs=0.83 h^-1（R²=0.9750），且12 h后KMnO₄释放率为82.7%；SRPG可有效降解水中氯代烃污染物，其中对三氯乙烯（TCE）的去除效果最佳，反应24 h可去除水中98%的TCE.因此，SRPG在原位化学氧化修复土壤和地下水中氯代烃的实际工程中具有良好的应用前景.