Environment Monitoring and Measurement

Environmental monitoring and measurements are helpful in environmental assessments , as well as in many circumstances in which human activities carry a risk of harmful effects on the environment. All monitoring strategies and programs have reasons and justifications which are often designed to establish the current status of an environment or to establish trends in environmental parameters. Knowledge gained from this information can be used to implement corrective and preventive action. Key characteristics are those that the organization needs to consider to determine how it is managing its significant environmental aspects, achieving objectives and targets, and improving environmental performance. In order to ensure valid results, measuring equipment should be calibrated or verified at specified intervals, or prior to use, against measurement standards. Refer ISO 14001:2004 Clause 4.5.1

Sampling Techniques

There are a various methods of sampling which depend on the type of environment, industrial processes, the material being sampled and the subsequent analysis of the sample. It is sometimes as simple as filling a clean bottle with waste water and submitting it for conventional chemical analysis and complex using electronic sensing devices taking sub-samples over fixed or variable time periods and computing them to come out at end results with the help of instruments and equipments

GRAB SAMPLING

Grab samples are samples taken of a homogeneous material, usually waste water, in a beaker or sample bottles. Grab samples provide a good snap-shot view of the quality of the sampled waste water at the point of sampling and at the time of sampling. Without additional monitoring, the results cannot be extrapolated to other times or to other parts of the waste water or ground-water. One should ensure that the grab sample must be the representative sample of the water body. Grab samples are more appropriate for small plants with low flows and limited staffs who cannot perform continuous sampling. Grab samples do provide an immediate sample, and are thus to be preferred for some tests such as pH, dissolved oxygen, total residual chlorine.

Composite Sampling

It is a fact that sometimes mixing two or more grab samples may not result in average of the characteristics of the waste water samples. Chemical reactions can take place in mixed samples which alter pH and chlorine residual values. Composite sampling is also known as an integrated sampling which consists of a mixture of several individual grab samples collected at regular and specified time periods, each sample taken in proportion to the amount of flow at that time. Composite samples give a more representative sample of the characteristics of water at the plant over a longer period of time. The benefit of composite sampling is their ability to take into account changes in flow and other characteristics of the water/waste water over a period of time. This helps the sampling team to gain an overall picture of the total effects that the influent will have on the treatment process and that the effluent will have on the receiving water. However, composite samples cannot be used for tests of water characteristics which change during storage such as dissolved gases or of water characteristics which change when samples are mixed together such as pH.

Monitoring locations and Parameters

Predominant wind direction plays an important role in determining location of monitoring stations. Due to effects such as land and sea breezes, valley effects etc. it is important to collect local meteorological data specific to the site. The monitoring stations should be located in areas that are downwind from the sources. Mixing height data should also be collected. Mixing height data can be collected from Indian Meteorological Department.

Information on duration of various seasons in a year is also important. Measurement frequency should be such that monitoring is done in all the seasons so that all seasonal variations are included in computing annual average. Parameters such as Sulphur Dioxide (SO2), Oxides of Nitrogen as NO and Suspended Particulate Matter (SPM) and Respirable Suspended Particulate Matter  (RSPM/PM10), toxic trace metals, Hydrogen Sulphide (H2S), Ammonia (NH3), and Polycyclic Aromatic Hydrocarbons (PAHs) are monitored in Ambient Air.