[Effects of extremely low frequency electromagnetic radiation on cardiovascular system of workers].

OBJECTIVE: To observe the exposure levels of extremely low frequency electromagnetic fields in workplaces and to analyze the effects of extremely low frequency electromagnetic radiation on cardiovascular system of occupationally exposed people. METHOD: Intensity of electromagnetic fields in two workplaces (control and exposure groups) was detected with EFA-300 frequency electromagnetic field strength tester, and intensity of the noise was detected with AWA5610D integral sound level. The information of health physical indicators of 188 controls and 642 occupationally exposed workers was collected. Data were analyzed by SPSS17.0 statistic software. RESULTS: The intensity of electric fields and the magnetic fields in exposure groups was significantly higher than that in control group (P < 0.05), but there was no significant difference of noise between two workplaces (P > 0.05). The results of physical examination showed that the abnormal rates of HCY, ALT, AST, GGT, ECG in the exposure group were significantly higher than those in control group (P < 0.05). There were no differences of sex, age, height, weight between two groups (P > 0.05). CONCLUSION: Exposure to extremely low frequency electromagnetic radiation may have some effects on the cardiovascular system of workers.

[Simultaneous nitrogen and phosphorus removal by aerobic granular sludge at normal and low temperatures].

The simultaneous nitrogen and phosphorus removal (SNPR) from real domestic wastewater using aerobic granular sludge (AGS) has been investigated. The effect of temperature changes on the SNPR of AGS was also studied. Two lab-scale sequencing batch reactors (SBRs), named as A and B, were operated for 254 days in alternating anaerobic-aerobic mode. The AGS was cultivated in 20 days using settling time as selection pressure. From the 42nd day onwards, additional carbon (acetate and peptone for A, glucose for B) were added to make the ratio of COD:N:P as 360:60:6. The SNPR by AGS was achieved for 4 months, and the removal ratios of ammonia, total inorganic nitrogen and phosphorus of A were reached to 98.42%, 74.25% and 94.79%, respectively; the removal ratios of ammonia, total inorganic nitrogen and phosphorus of B were reached to 99.45%, 75.96% and 95.60%, respectively. Then, the temperature decreased to 9-13 degrees C, which seriously affected the efficiency of SNPR. The removal efficiencies of SNPR of reactor A and B were recovered after 35 days and 49 days, respectively, and the removal ratios of ammonia, total inorganic nitrogen and phosphorus of A were reached to 96.33%, 79.49% and 99.68%, respectively; the removal ratios of ammonia, total inorganic nitrogen and phosphorus of B were reached to 93.85%, 76.44% and 98.44%, respectively. PAOs and DNPAOs together completed the phosphorus removal and made phosphorus removal faster than nitrogen removal. Nitrification was the rate limiting step for SNPR. The low temperature made the anoxic zone in AGS decrease, together with the absence of PHAs, made denitrification could not complete.