The factor analysis of water resources and energy security in Shenzhen in 1996–2015 was carried out. Economic and average factor (f₁), population and elasticity factor (f₂) are two main factors. f₁ shows the threat of supporting the city’s normal operation to water resources and energy security, with a weight of 68%. f₂ shows the uncertainty brought about by the increments of economic and population to water energy system safety, with a weight of 32%. The composite score shows that the total water energy system safety in Shenzhen tends to decline. This conclusion accords with the actual situation of water energy system in Shenzhen municipality. It shows that the evaluation model is effective for the analysis of water energy security situation in Shenzhen, and can provide reference for the decision-making of Shenzhen municipality.

A decompression-dehydration-drying system was designed and improved to deal with cutting fluid wastewater produced during metal processing. The results show that the removal rate of total suspended solids is more than 99.38%, and the average removal rates of n-HEX, BOD5, COD_Mn, total nitrogen, total phosphorus, copper and zinc are 99.07%, 96.67%, 98.64%, 81.28%, 99.33%, 98.69% and 99.79% respectively. Combined with ozone treatment it can further improve the removal rate of organic pollutants. Compared with other treatment methods, during the process of sewage treatment, the proposed system produces very little smell and noises, and do not need a large number of chemical agents, and has a small footprint and low cost. It is especially fit for the treatment of highly concentrated cutting fluid wastewater.

Based on the survey of household photovoltaic demonstration project in Xinyu City of Jiangxi Province, stable investment recovery period and internal rate of return (IRR) are applied as the economic evaluation index, the energy recovery period and annual savings of standard coal as the environmental benefit evaluation index, the generation power, revenue composition and economic benefits under different circumstances, environmental benefits of 5 kW household photovoltaic system were analyzed. The results show that the yearly power generation of 5 kW household photovoltaic system is 4056.7 kWh, only 79% of the theoretical value. The system has a good economic benefit with the subsidies from the state and Jiangxi Province. The stable investment recovery period is less than 8 years, and the internal rate of return is 11.2%. Lack of subsidies from the state or Jiangxi would have a large impact on the economic benefits of investments. The photovoltaic system also has a good environmental benefit, saving 1.46 tons of standard coal each year, and the energy payback period is 5.22 years. The development of household photovoltaic needs support of national policy and appropriate promotion model.

The research monitored the water quality regularly and analyzed its spatial and temporal changes from 2014 to 2015 in the Futian Mangrove National Nature Reserve. Based on the water quality monitoring results from 2009 to 2014, the annual variation trend of water quality was also studied. The results showed that the DO was generally lower, and the average concentrations of TN, TP, COD and BOD, were 4, 2.6, 1.3 and 1.3 times higher than the class V standards of surface water respectively, the water was in heavy eutrophication status. The pollution level in dry season was significantly higher than in rainy season. From 2009 to 2014, the average concentrations of TN and TP showed a trend of decreasing firstly and then increasing, the BOD values kept rising and the COD values kept falling. Instead of heavy metals pollution, it was the organic pollution, mainly coming from the exogenous input, which have been the key problem of the water pollution, and it needs to take measures to control the pollution immediately.