Effluent Standards are usually imposed with the Quality and Discharge Limits set based on the needs of the receiving streams, its locations and in particular on whether the streams have extended use and serve towards other purposes. Those which do not contribute as source for potable and drinking water may not have discharge standards as strict as those streams that flow directly to the sea without passing through residential areas and depending on the regulatory bodies or governmental agencies, it is up to them to set and control the rules. Therefore, the limits on different parameters can vary not only from one state to another but also within the same locality and in particular depending on which receiving streams the discharge effluent goes to. Certain countries, which are more environmental conscious, will set higher standards and quality for their domestic and industrial discharge and there is also a guideline to control the monitoring parameters applied for different industry categories.
There are a few quality limits which are often monitored as part of the wastewater discharge control standards and the most important are COD, BOD, dissolved oxygen, suspended solids, nutrient levels, pH and bacteria. COD and BOD which indirectly relates to the amount of organic and non-organic compound can contribute towards serious environmental pollution if there levels are left unchecked before releasing to the streams. Breakdown and decomposition of these materials which otherwise should have taken place in a treatment plant, instead happens in the natural streams and because of that it will deplete the oxygen level, creating anaerobic condition that will kill all the aquatic organisms. High amount of suspended solids may settle to the bottom of the river and this result in sludge build up. When decomposition occurs, further oxygen demand will be exerted which will lead to oxygen deprivation and foul odor generation. Similarly, the dissolved oxygen content of the effluent discharge also becomes an important issue because if the DO levels drop below the 4 to 5ppm limit, this will have serious detrimental effects towards survival of the aquatic species.
In the United States for example, enforcement of effluent regulations and the procedures affecting wastewater discharge are bound and set in accordance to the Clean Water Act which becomes the basis and framework not only for development of discharge control systems but also on the legal aspects as well. Regulations set by each state are always subject to change depending on a case-by-case evaluation of potential environmental impacts and the receiving water bodies; with more focus especially on how it can affect public health if there is any harmful toxic substance still present in the wastewater after it has undergone treatment process. Basically, contaminants present in effluent can be divided into organic and non-organic compound. Most organic substances usually do not pose much concern as these are easily biodegradable and furthermore do not bring much adverse harmful effect. Those that raise serious concerns are usually the synthetic organic compounds or toxic refractory organic substances which are difficult to break down by microorganisms and these are widely used in agriculture chemicals and other manufacturing plants. Those inorganic substances like heavy metals can also be very difficult to contain and removed in wastewater treatment facility and as such discharge permits are issued with the limits focused on these few important parameters.
Effluent discharge standards not only cover on the subject of setting the parameter limits but there are also other aspects as well related to training and education on improving staff competency, record keeping on the treatment processes, performance monitoring plan and part of it also includes the maintenance schedule. Usually it is a common practice governed under the law and legal framework, made mandatory for new companies or those presently with plans on capacity upgrading or expansion program to submit the paperwork in order to notify the regulatory bodies on their wastewater treatment program. A comprehensive study and proposal will be submitted to explain and to seek approval on whether the current treatment plant capacity is enough to handle the expansion before the permit can be issued. This is needed before the project is allowed to start work or commence operations.
Sometimes, newly set up companies especially those in the industries that generate high-strength wastewater with toxic pollutants are not aware of the consequences in particular the legal aspects, and the situation is further compounded if they do not have any prior experience and vast knowledge in the treatment field. Comes to this situation, the best approach is to seek the advice of wastewater consultancy firm so that they can guide and provide expert opinions on the way forward.