Problems encountered in practice

- Apr 24, 2020-

Water quality standards are an important basis for the national environmental protection department to carry out administrative management to ensure good water quality. Since the 21st century, the country has revised the "Surface Water Environmental Quality Standards" (GB 3838-2002) according to the current situation in which the types of organic pollutants in the environment and the environmental exposure concentration have increased dramatically. The biggest improvement of the new standard is the addition of a large number of organic indicators, the number of indicators reached 109. The new standard requires all provincial monitoring departments to implement full-index monitoring in the near future. This puts new and higher requirements on the monitoring work of the provincial monitoring departments. However, the routine monitoring work of the provincial monitoring departments is still based on the conventional indicators in the national standard, and the non-conventional indicators (mainly organic indicators) have fewer types of monitoring, lower frequency, and limited experience accumulation. Through summarization, the editor summarized that "Surface Water Environmental Quality Standard" (CGB 3838-2002) is easy to find problems in the process of practice, so that readers can avoid repeating the same mistakes.

At present, the water quality monitoring of the problems encountered during the process of the surface water environmental quality standard (GB 3838-2002) includes the following aspects: ① water sample collection; ② fixation; ③ transportation; ④ preservation; ⑤ pretreatment; ⑥ analysis. The monitoring methods for indicators of basic and supplementary projects in Surface Water Environmental Quality Standards (GB 3838-2002) are relatively mature, and the monitoring can be carried out smoothly; while in the monitoring process of nearly 70 kinds of organic indicators in specific projects, all of the above links are encountered Many issues are briefly discussed below.


(1) The current "Technical Specifications for Surface Water and Sewage Monitoring" is not operable in the supervision of all indicators

To ensure accurate and reliable monitoring results, water samples should be fixed, transported and stored after collection. At present, the requirements for collection, fixation, transportation, and preservation in the "Technical Specifications for Surface Water and Wastewater Monitoring" are more stipulated separately for single indicator monitoring, and are suitable for routine monitoring with fewer monitoring indicators. However, for the monitoring of all indicators, due to the large number of indicators and the different natures, it is more difficult to fix the water samples on site for each indicator, and the operability is not strong.


(2) Lack of pretreatment method system for multiple organic indicators

After the water sample is collected, fixed, transported to the analysis site and stored properly, the pretreatment of the water sample needs to be performed before the analysis. The pretreatment of a large number of water samples should be carried out as soon as possible, and there are many organic matter indicators. The pretreatment methods of each organic matter indicator are different. According to the current national standard method, the water sample pretreatment time is longer. In addition, various pretreatment methods face different levels of operational difficulties, such as the purification of water samples, the separation of the organic and aqueous phases during liquid-liquid extraction, and the solid phase extraction that requires a large number of water samples to be filtered, etc. Problems that need to be solved urgently in the pretreatment of water samples.


(3) Inferior reagents have serious disturbance to water sample monitoring

The monitoring of the full index of the water sample requires a large amount of chemical reagents, and the high quality reagents are the guarantee of the monitoring work. However, in actual work, we found that some of the chemical reagents currently on the market cannot meet the monitoring requirements and cause serious interference to the monitoring work (such as poor quality potassium persulfate interferes with total nitrogen analysis, poor quality extraction solvents interfere with organic matter analysis, etc.


(4) Purchase of individual monitoring index standard and essential reagents delayed the monitoring due to difficulties

At present, there is no unified subscription channel for the standard products specified by the national standard. The standards, reagents and drugs required for our monitoring work are obtained from the supplier information through the network, and they are purchased one by one. The purchase cycle is long. Individual standards such as high-purity microcystin Difficult to buy domestically. In addition, the reagents required for the pretreatment of some indicators are highly toxic, highly corrosive, explosive and other dangerous goods, such as potassium oxide, mercury iodide, acetic anhydride, etc., and procurement must be applied step by step. These additional difficulties have delayed the monitoring work.


(5) At present, the recommended analysis method of the national standard cannot meet the monitoring requirements of the whole index well

Analyze each index based on the index monitoring method recommended in Surface Water Environmental Quality Standard (GB 3838-2002). The method recommended in this standard is feasible for each single index.


However, the national standard recommendation method is too singular, and many of the indicators with similar properties and proven by the same method have different national standard recommendation methods, which increases the work intensity, prolongs the monitoring period, and reduces the operability of full index monitoring. (Chlorobenzene indicators, nitrobenzene indicators, etc.). In addition, there is no national standard method for the two indicators of benzidine and PCBs; the recommended methods of individual national standards cannot meet the needs of indicator determination (such as trichloroethane).


(VI) The water quality standards are not uniform

While focusing on the surface water quality standard "Surface Water Environmental Quality Standard" (GB 3838-2002), we also pay attention to other water quality standards in China, such as user water quality standards "Sanitary Standards for Drinking Water" (GB5749-2006), water plants Effluent water quality standard "City Water Supply Quality Standard" (CJ / T206-2005), etc. The comparative study of various standards shows that the user water use index limit is generally stricter than the surface water index limit, and the water plant effluent index limit is generally stricter than the user water index limit. This is consistent with the actual situation of water quality changes.


However, there are still inconsistencies and inconsistencies among the standards. If the individual index limit of the water plant ’s effluent is higher than the user ’s water use limit [such as bis (2-ethylhexyl) phthalate], the water plant ’s effluent regulation monitoring index is less than the user ’s water regulation monitoring index (such as trichloroethane Aldehyde) etc. In addition, the "Sanitation Standards for Drinking Water" (CB5749-2006) also has the phenomenon that the national standard method cannot meet the monitoring requirements of indicators, such as epichlorohydrin.


Conclusion

Although the above six major problems are often encountered in the implementation of the "Surface Water Environmental Quality Standards", the editor believes that there are more problems or unreasonable waiting for detection personnel to discover. It is hoped that through these problems, we can let the inspectors summarize the problems encountered during the implementation of the standard and avoid losses.