Odor and taste checking experiments
Odor and taste checking experiments
For the food industry, by the environmental impact of the biggest factor is water, while food processing and pollution of the water environment, in order to prevent and control water pollution must understand the types of pollutants and content characteristics, etc., which all need to analyze and test the water samples, the collection of water samples, preservation and pre-treatment of the appropriate or not on the test results play a very big role. This experiment is mainly for students to study the regional water pollution survey, and understand the pathways and hazards of water pollution, mastering the collection and preservation of water samples and the methods and steps.
Operation method
Water pollution investigation and water sample collection, preservation and pretreatment experiments
Materials and Instruments
Milled Bottle Plastic Bottle Move I. Experimental methodology For more product details, please visit Aladdin Scientific website.
(i) Determination of the selection of survey points
According to the regional water resources, water pollution situation to determine the investigation point, analysis of the main causes of pollution according to the results of water-related physical and chemical indicators and consulting survey results.
(B) the choice of sampling points
The representativeness and reliability of the samples depends on the representativeness of the sampling section and sampling point. In order to reasonably select the sampling section and sampling point, should do a good job of investigation and research work, collect the hydrology of the water body, climate, geology, geomorphology, the unit in the city's specific location, the entire industrial layout, sources of pollution, transportation, biological and sedimentary materials.
This experiment is intended to collect domestic water and wastewater samples for some of the indicators of the test, in order to give students a preliminary understanding of the basic principles and methods of water sample collection, preservation and pretreatment.
(iii) Sampling methods
1. Sampling bottle preparation
Containers for water samples are colorless rigid bottles or polyethylene plastic bottles. Before sampling, wash the glass bottle with 10% hydrochloric acid, hot soapy water, bleach solution or synthetic detergent and any other kind of washing solution, and wash with distilled water. Bottle stoppers are best used with ground glass stoppers, rubber stoppers, or cork stoppers, and the use of wood, paper dough, and metal for stoppers is absolutely prohibited. When using rubber stoppers, respectively, with 10% sodium carbonate solution, (1 + 5) hydrochloric acid solution, and then boiled in water, and washed with distilled water. When cork is used, it is first boiled in distilled water and then washed with distilled water.
In the sampling must also be collected before the water sample will be used to wash the container 2 to 3 times. Regardless of the collection of water samples, should be equipped with a screen in the water intake pipe of the water collection device, to prevent the floating matter in the water to clog the pump and the sensor.
2. Surface water collection
Buckets, bottles and bags can be used as a water collector, gently put into the water surface 20 ~ 50 cm or 30 cm from the bottom of the water directly collected water samples. Immediately after sampling, stopper the bottle tightly to prevent the water sample from contacting the air or surface water contained in the floating matter into. This method is not applicable to the collection of dissolved gases and reducing substances.
3. Collection of deep water
The collection of deep water samples, available sample containers water collector, single-layer water collector, multi-layer water collector, Hailot water collector, inverted water collector, Banton water collector and suction pumps and other specialized equipment, respectively, from different depths to collect water samples.
4. Wastewater collection
Due to the production of different products and processes, the composition of food industry wastewater varies greatly. Wastewater discharge time also varies according to the wastewater production, in a day and night or a few days and nights in the collection of wastewater in the average water samples or the average proportion of water samples as well as the peak concentration of water samples. Because some factories are not regularly discharged every day, so for the collection of the average proportion of water samples, that is, when the flow rate is large, take more, the flow rate is small; on the contrary, when the flow rate of wastewater is more constant, it is only the collection of average water samples. Regardless of the average water sample or average proportion of water samples, generally should be collected for a day and night, each water sample poured into a clean bottle mixed for analysis and determination of use. When mixing the water samples, the substances in the water samples should be prevented from changing.
If the wastewater is discharged intermittently, then wastewater representative of production and domestic processes should be collected.
5. Collection of natural water
When collecting well water, it can be collected directly by water collector such as cylinder and bottle. When collecting tap water, the faucet should be opened first, and the water in the pipe should be drained for 3-5 min, and then the water sample should be filled. Collection of spring water, such as if the fountain water, can be directly sampled in the emergence of water sampling, or sampling with the pumping valve. When collecting rainwater, use a general rainfall device (simple dust collector, large water collection disk) to directly collect the amount of rainfall or snowfall for a certain period of time.
(D) Sampling volume
The size of the sampling volume by the analysis of the number of items determined. Because the analysis of the project often have different requirements for the amount of water samples and preservation conditions, so the sampling volume should be calculated in accordance with the actual needs of each monitoring project, and then appropriately increase the amount of water samples by 20% to 30%, as a test of the project's actual sampling volume.
(E) the preservation of water samples
Each type of water samples allowed to store time is different, clean water for 72 h, mildly contaminated water for 48 h, seriously contaminated water for 12 h. The water samples should be stored in the same manner as the water samples.
If the water samples are placed too long, due to physical, chemical, biological effects and often cause a reduction in the concentration of the components to be measured, change the nature of the water samples, which in turn affects the analysis results. Therefore, the shorter the time interval from sampling to measurement, the more reliable the analytical results. However, water samples in transit or can not be immediately analyzed and measured, certain measures must be taken to properly preserve the water samples to ensure the accuracy of the analysis results.
There are many ways to preserve water samples, however, there are fewer ideal preservation methods. Common preservation methods include freezing and chemical methods.
1. Freezing preservation method
The use of freezers or refrigerators, water samples will be stored in the dark at 4 ℃. In this way, it can prevent microbial reproduction, slow down the rate of physical action and chemical changes, reduce the volatilization of components. With this method of preservation, organic matter can be preserved unchanged without affecting the results of the analysis. Therefore, low-temperature preservation such as utilizing dry ice is considered to be the best preservation method, but at a higher cost.
2. Chemical preservation method
In the water samples, add a certain amount of chemical reagents as inhibitors, biocides or preservatives, inhibit the role of microorganisms, or adjust the acidity of the water samples, to prevent precipitation, hydrolysis, redox, complexation reaction, so that the composition of the water samples, the state of the water samples and the valence of the state of the water samples to maintain relative stability.
3 Management of water samples
Samples are obtained from a variety of water bodies and various types of water physical evidence and information, water samples proper and strict management is a necessary means of obtaining reliable monitoring data, this standard specifies the management of water samples and procedures.
3.1 label design of water samples
After the collection of water samples, often according to different analytical requirements, divided into several parts, and add preservatives respectively. For each sample should be accompanied by a complete water sample label. The design of the water sample label can be based on the actual situation, generally include: sampling purpose, subject code, the number of monitoring points, location, monitoring date, time, sampling personnel and so on. The label should be filled out with non-fading ink and securely attached to the outside of the container holding the water sample.
Items requiring field testing, such as pH, conductivity, temperature, flow rate, etc., should be recorded in accordance with Table 2, and the field records should be properly maintained (see Table 2).
3.2 Transportation of water samples
Containers with water samples must be properly protected and sealed, and packed in a box fixed to prevent breakage in transit, including materials and conditions of transportation of water samples should be strictly required. In addition to shock protection, avoidance of sunlight and low-temperature transportation, it is important to prevent new contaminants from entering the container and staining the mouth of the bottle to deteriorate the water sample.
During the transfer of water samples, each water sample should be accompanied by a management program registration card (see Table 3). When transferring water samples, both the transferor and the receiver must count and examine the sample and sign the registration card with date and time.
The management procedure registration card is a document of the water samples during transportation and must be kept in a safe place to prevent errors and for inspection. It is particularly important when water samples are transferred from the sampling site to the laboratory analyst through a third party (see Table 3).
3.3 Receipt of water samples by the Laboratory
When water samples are delivered to the laboratory, the first thing to do is to check the water samples, check the labels, and sign for acceptance when they are correct.
If it can not be immediately analyzed, it should be taken as soon as possible to save measures, and to prevent contamination of water samples. 
