Control Of Wastewater Treatment Process Research Articles

Activated sludge process monitoring through in situ near-infrared spectral analysis

The application of near infrared (NIR) spectroscopy for industrial process monitoring is achieving increasing importance over the last twenty years. In fact, the real time monitoring capacity of NIR spectroscopy is a very important feature for process monitoring, prediction and control as it allows a fast evaluation of the state of the process. However, the application of NIR spectroscopy in wastewater treatment processes is still to be explored. Although some applications of the technique for wastewater monitoring have been reported in the literature, there is still a need for more investigation related with applications, limitations and advantages of the technique when compared with other methods. An activated sludge reactor for aerobic treatment of a complex medium was monitored in situ with a NIR transflectance probe and traditional chemical parameters analysed off-line. NIR spectrophotometric data measured at the feed, reactor and settler were coupled to principal component analysis (PCA) to infer about the ability of this monitoring system to detect changes in the feed influent. The analysis of the score plots resulting from PCA permitted to identify the moments at which the perturbations occurred and to follow the consequent instability induced in the reactor till the day where the system is recuperated. The promising results obtained, suggest the interest in more detailed studies on the feasibility of NIR spectroscopy as an alternative method for monitoring and control of wastewater treatment processes.

Selection of variables using factorial discriminant analysis for the state identification of an anaerobic UASB–UAF hybrid pilot plant, fed with winery effluents

Anaerobic wastewater treatment has become a widely used method for wastewater depuration, and has been applied in a wide range of situations, from urban wastewater to highly toxic industrial wastewater. Particularly it has been successfully applied to the treatment of the beverage industries effluents. To avoid the destabilization of the system a monitoring diagnosis and control system of the depuration processes is necessary. The cost of this system is an important issue, that depends on the number of parameters that must be controlled for an adequate performance of a wastewater plant control system. This work shows how the classic statistical classification techniques can be applied to determine the number variables that must be monitored to achieve an adequate performance of anaerobic UASB-UAF hybrid Pilot Plant monitoring and control system. The obtained results had not been unique, so different combinations of variables can be selected for a good wastewater treatment process control. Economic or technical criteria may be considered to determine the final variables set in each particular situation.

QFT ROBUST CONTROL OF A WASTEWATER TREATMENT PROCESS

The paper deals with the wastewater treatment process control using QFT (Quantitative Feedback Theory) techniques. The aim of the control is to obtain an effluent having the substrate concentration within the standard limits established by law (under 20 mg/l). It has been admitted variable operating regimes in large limits. Three main regimes have been taken into account: rain, normal, and drought. In these conditions two aspects were considered: a QFT controller designed to assure good properties for the three regimes mentioned before; a control structure that adjusts the dissolved oxygen setpoint as a function of the influent regime. The purpose is to stabilize the operating regime with respect to the quality variable (the effluent substrate concentration) and the command variable (the dilution rate).

The activated sludge biomolecular database.

Tremendous advances have recently been made in the development of molecular tools for analysis of microbial populations in the environment. However, an appropriate scientific basis for quantification of new molecular data must exist to effectively use these tools toward increased understanding of complex waste treatment environments and implementation of corrective actions to maintain or improve system performance. In particular, molecular tools are gaining widespread use in the study of activated-sludge microbial communities and have the potential to improve monitoring and control of wastewater treatment processes. The authors have created a Web-accessible database, the Activated Sludge Biomolecular Database, which provides a scientific basis for interpreting activated-sludge biomolecular information. The database achieves its goal by accumulating and disseminating a large body of knowledge relating the presence and quantity of specific biomolecules to process design, operating conditions, and wastewater characteristics.

Inhibiting effects of chloroform on anaerobic microbial consortia as monitored by the rantox biosensor

The Rantox biosensor was designed for anaerobic wastewater treatment process control, and detects modifications of the feed based on the response of the acetoclastic methanogens contained in the sensor to periodic pulses of a concentrated organic substrate. The biosensor was tested under various operating conditions at the laboratory scale, in parallel with a digester under control fed on the same substrate. The aim was to evaluate the response of the biosensor in the presence of an incoming organic toxic compound (CHCl 3). The experimental set-up, i.e. the biosensor and the digester, was connected to an automated control system developed under LabVIEW ® environment for data acquisition and operational sequence programming (the Rantox Virtual Instrument). Biomasses with different activities were used as inocula, and inhibition was induced by dosing chloroform according to two different procedures. The results showed good sensitivity and rapid response of the biosensor to feed intoxication. The presence of chloroform was detected by the Rantox with a rapid and visible response, and well in advance with respect to the digester.

Benchmarking for process control: “should i invest in improved process control?”

Benchmarking to achieve world class performance is becoming an increasingly popular technique in all business sectors. In this paper, we benchmark wastewater treatment process control practice against other process industry sectors in Australia, and provide an evaluation of the general level of process control in the wastewater treatment industry. The benchmarking is based on criteria developed by ICI Engineering. We also present a quantitative statistical tool which can be used for performing a benefits analysis.

Benchmarking for process control: “Should i invest in improved process control?”

Benchmarking to achieve world class performance is becoming an increasingly popular technique in all business sectors. In this paper, we benchmark wastewater treatment process control practice against other process industry sectors in Australia, and provide an evaluation of the general level of process control in the wastewater treatment industry. The benchmarking is based on criteria developed by ICI Engineering (Brisk and Blackall, 1995). We also present a quantitative statistical tool which can be used for performing a benefits analysis.

Characterization of a prototype industrial on‐line analyzer for bicarbonate/carbonate monitoring

In many biological reactors bicarbonate is the major species determining pH buffering capacity, or alkalinity. In anaerobic digesters bicarbonate levels should be within 10 to 50 mM for stable operation. Bicarbonate alkalinity in wastewater treatment processes in routinely measured off-line titrimetrically. Recently we have described the principle of a novel on-line method of measuring bicarbonate alkalinity. In the prototype device described here, a continuous stream (15 cm(3) min(-1)) of the substrate to be monitored was saturated with gaseous CO2, acidified by the addition of excess acid, and the rate of carbon dioxide evolution, proportional to the concentration of bicarbonate/carbonate in the liquid flow, continuously measured by a sensitive gas meter. The instrument was robust and its response was satisfactory for wastewater treatment process control applications, with linearity in the range 5 to 50 mM HCO3(-), a response time in the order of 30 min, and accuracy of the order of 7% in the concentration range 5 to 50 mM sodium bicarbonate. The device was not affected by interference from volatile fatty acids, does not make use of pH probes which in many wastes are subject to fouling, and may form the basis of a digester control strategy.

Optimizing Bioassay Use in Environmental Management through Test System Selection

Bioassays, the use of a living system to test or assay an effect or response, are finding expanding use in environmental management. Testing procedures have become standardized and new technologies support development of biosensors with the sensitivity and accuracy needed for routine application in monitoring and assessment programs. While new methods allow more accurate and sensitive detection of biological response, if response measurement is not connected with an environmental or ecological consequence, testing may have little use in management or regulation. It is possible to optimize bioassay use in environmental management by following study design assurance procedures that carefully select testing procedures and batteries of tests to meet defined objectives. This paper first reviews procedures for selecting measurement metrics for wastewater treatment process control and environmental assessment. Test systems are suggested that optimize bioassay use in the management of complex environmental systems. For example, an ecological paradigm can be applied to wastewater treatment processes as well as receiving water ecosystems. This paradigm considers both the structure and function of the system in selection of measurement metrics and test batteries in the development of a test system. Examples are provided that demonstrate how optimal bioassay use can lead to improved environmental management.

Development and Analysis of Equalization Basins

Adequate control of wastewater treatment processes with variable input parameters can be achieved through the employment of equalization basins. Variability of input and output parameters are analyzed, and mathematical models of conventional and new configurations of equalization basins describing the propagation of regular and random input signals are presented. Comparison of various designs of equalization basins show that new configurations of equalization basins are more efficient than one‐channel tanks (complete mix, m‐tanks in series, or diffused flow). A substantial advantage of new basin types is in that they can be tuned to the particular spectrum of incoming fluctuations.

Instrumental Analysis in Wastewater Treatment

Analytical chemistry is central to monitoring the operation of wastewater treatment systems. This paper reviews briefly the development of wastewater treatment and the early analytical procedures used in the monitoring of these systems. The major focus is on the application of instrumental techniques to wastewater treatment process control and effluent monitoring. The classical methods of analysis included gravimetric, bioassay, titrimetric, electrometric and colorimetric. Modern methods include atomic absorption spectrophotometry, gas chromatography, x-ray fluorescence, laser Raman spectrometry, ion-selective electrodes, nuclear magnetic resonance and on-line analyzers. Summaries and comparative tables were included for both methods. 2 tables. (DP)