Effluent Violations Research Articles

New Process Design Procedure for Dealing with Variable Trickling Filter Effluent Suspended Solids

Based on a survey which showed that seven of eight conventional trickling filter (CTF) plants exceeded the U.S. Environmental Protection Agency secondary treatment regulatory requirements, a new design procedure is proposed. It recognizes that bioflocculation within CTFs is poor and that most of the effluent violations seen in the survey could be related directly or indirectly to the level of effluent suspended solids. In past practice, process design focus has been on soluble or settled effluent biochemical oxygen demand ( BOD5 ) rather than the effluent suspended solids. The principal focus in CTF process design should be on predicting effluent suspended solids (SS) after secondary clarification, rather than effluent carbonaceous BOD5 . If the total organic loading (TOL) is set in the proper range, the effluent carbonaceous BOD5 is primarily determined by the effluent SS. A new design procedure has been developed that identifies the highest TOL that can be sustained without posing a constraint on efflue...

Wastewater treatment benchmark: what can be achieved with simple control?

In this paper a simple control strategy is applied to and assessed on the wastewater treatment benchmark. The controllers used in the presented control strategy are PI controllers, feedforward control and a step-feed procedure. The controlled variables are not directly the effluent concentrations but other process variables which have an effect on the effluent. The setting of set-points is also analyzed to select the values with the best performance. Set-point analysis has shown that with an optimal setting of set-points under stormy influent conditions, the achieved plant performance is also retained for rainy and dry influent conditions. The evaluation of plant performance indicates that with the proposed control strategy, a lower number of effluent violations has been achieved, as well as lower energy consumption and lower sludge production, when compared to results published up to now. Only the effluent quality criterion deteriorated.

Is CBOD 5 Test Viable for Raw and Settled Wastewater?

In recent years, the carbonaceous biochemical oxygen demand ( CBOD5 ) test has been employed to determine the carbonaceous fraction of the biochemical oxygen demand ( BOD5 ) of final effluents in nitrifying systems. More recently, several states have required plants to analyze influents using the CBOD5 test to determine whether the 85% removal rule is being attained. The 1989 Standard for the Examination of Water and Wastewater Methods does not suggest—nor does the Environmental Protection Agency (EPA) CBOD5 procedure studies justify—the use of the CBOD5 test for raw and settled wastewaters. Analysis of operational data from several plants demonstrates that the CBOD5 test seriously understates the true strength of influent and primary effluent wastewaters as defined by BOD5 and chemical oxygen demand ( COD ) tests. The result of using CBOD5 data could result in a 20–40% underdesign as well as cause nonexistent effluent violations of the EPA 85% removal criteria rule. The conclusion was that CBOD5 is an im...

Model of Algal Bacterial Clay Wastewater Treatment System

A computer model is presented for an innovative wastewater treatment process known as the Algae-Bacterial-Clay Treatment (ABCT) system. In this process the photosynthetic production of dissolved oxygen by algae supports the bacterial breakdown of organic matter in wastewater. Clay is added to the plug flow reactor to dampen input BOD variation. The model was developed to gain an improved understanding of transient behavior of dissolved oxygen and pH in the treatment reactor during typical operation. The model consists of five nonlinear ordinary differential equations describing the time rate of change of algae mass, bacterial mass, organic substrate, dissolved oxygen, and dissolved carbon dioxide. A fourth-order Runge-Kutta integration technique was used to predict system response at discrete time steps. The pH variation expected from changes in dissolved carbon dioxide was based upon presumptions that the system is buffered by the carbonic acid system, and that alkalinity does not change appreciably during the course of time. These assumptions were confirmed by experimental results. The model successfully predicted diurnal fluctuations in dissolved oxygen, carbon dioxide, and pH in the ABCT process. The model predicted that algae will supply sufficient oxygen during sunny and partly sunny days to eliminate the need for continuous mechanical aeration. This feature should result in significant cost savings over conventional secondary wastewater treatment schemes. Surplus dissolved oxygen produced by algae during the day should be completely depleted at night due to bacterial respiration. This lack of oxygen, in turn, resulted in reduced substrate utilization and potential effluent discharge violations. Mechanical aeration during the night might be one possible remedial strategy. Despite its dynamic behavior, the ABCT process would be a viable and potentially cost efficient wastewater treatment strategy.