Physicochemical Wastewater Treatment Research Articles

Physicochemical treatment of industrial wastewater with the multistage neutralization process

A complex industrial wastewater case is studied. The great variety of the products and the complexity of the production procedures render it impossible to apply a conventional technology for wastewater treatment. Initially an attempt was made to reduce the quantity and the organic load by reusing wastewater and by reclaiming useful substances or products from the wastewater. To further reduce COD the multistage neutralization process is studied by regulating the pH of the acid wastewater first in the alkaline region and then at pH 7. In this way COD removal is 18% greater than with the simple neutralization process at pH 7. Once this process was completed, since the effluent COD was not within the permissible limits, oxidation of the wastewater by using ozone was recommended.

Polar organic pollutants from textile industries in the wastewater treatment process — biochemical and physicochemical elimination and degradation monitoring by LC-MS, FIA-MS and MS-MS

Polar organic pollutants in textile wastewaters may give rise to problems in biological wastewater treatment. For the most part they are non-biodegradable, and their elimination is incomplete. The behaviour of these pollutants in biological, chemical and physicochemical wastewater treatment is followed with the help of substance-specific detection methods — liquid chromatography-mass spectrometry (LC-MS), flow-injection analysis-mass spectrometry (FIA-MS) and tandem mass spectrometry (MS-MS). No elimination was observed using biochemical and adsorptive procedures and there were insufficient results from the physico-chemical treatment.

Pilot Studies and Assessment of Downstream Effects of UV and Ozone Disinfection of a Physicochemical Wastewater

Abstract UV radiation and ozonation were investigated as disinfection alternatives for the Montreal Urban Community physicochemical wastewater treatment plant. The final effluent flows through a 5-km-long outfall tunnel before discharge into the St Lawrence River; the critical point for microbial quality is 4 km downstream. The study, therefore, also examined possible biofilm growth in the tunnel and dilution behaviour in the river. For UV disinfection, a newly developed, high-intensity medium-pressure lamp unit was tested because of its space-saving features. Typical two-stage dose-response curves were obtained with the transition between disinfection of free-swimming and particulate-associated organisms occurring at approximately 25 mW s/cm2. Disinfection behaviour improved when alum was substituted for FeCl3 as the coagulant. Photoreactivation decreased with increasing UV dose. Ozonation was adversely effected by changes in COD and H2S in the wastewater. A dose of 17 mg/L was needed to reach target disinfection levels of <5,000 CFU/100 mL in 90% of the cases; the CT value was approximately 0.4 mg min/L. Replacement of FeCl3 by alum reduced the required dose by 35%. Effects of biofilm growth in the tunnel were inconsistent: effluent SS and microbial concentrations were sometimes higher at the exit than at the entrance and vice versa. Effective dilution of microbes in the river decreased as water temperature increased, reaching a minimum of approximately 20.

Upgrading a low-cost physicochemical wastewater treatment plant to solve operational problems

A comprehensive programme of jar tests utilizing lime to treat municipal wastewater in northeast Brazil showed that a supernatant could be achieved that attained the WHO (1989) guidelines for effluent reuse for unrestricted irrigation (≤ 1000 faecal coliforms per 100 ml; ≤ 1 intestinal nematode egg per litre). In the light of these findings a pilot-plant was built to investigate the continuous treatment of wastewater with lime for effluent reuse in irrigation. Bearing in mind the problems often encountered in less-developed countries with the operation and maintenance of complex wastewater treatment systems, it was decided to base the lime treatment technology on that used successfully throughout the world (in both industrialised and non-industrialised countries) to treat potable water; namely non-mechanised coagulation and flocculation, and settlement in a horizontal-flow sedimentation tank. Although the prototype pilot-plant achieved a final effluent that attained the WHO (1989) guidelines for unrestricted irrigation, a number of operational and maintenance problems were encountered. Effluent quality data has been reported previously. This paper summarises the data and describes the practical problems associated with the operation and maintenance of the lime treatment plant, and the upgrading techniques used to overcome these difficulties. The prototype plant consisted of a rapid-mix basin in which raw municipal wastewater was combined with lime slurry at a ratio that achieved a pH of greater than 11.0 after mixing; a sedimentation tank, for solid-liquid separation; and a recarbonation basin for tertiary treatment. Constant monitoring of the lime-wastewater mix pH, using a pH controller to regulate the flow of lime slurry, proved difficult. Frequent cleaning of pipework was needed to avoid clogging by the lime slurry. In a second phase of the research work, the pilot-plant was upgraded to tackle these and other operational and maintenance problems. Plant geometry was improved to prevent the sedimentation of lime solids within the delivery pipework. All pipework carrying lime slurry was set up in duplicate so that plant operation could continue during cleaning operations. An improved pH control system, which linked lime slurry flow to the pH of the lime-wastewater mix, was also installed. The design of the sedimentation tank was altered to aid the removal of sludge and the tank inlet and outlet were upgraded in order to minimise short-circuiting. Plant operation and maintenance were simplified by the design improvements and the frequency of mechanical breakdown was reduced. The pH control system was difficult to operate effectively because the pH probe became rapidly fouled by lime solids. However, gel-filled, low sodium-error pH electrodes calibrated in pH 11.0 buffer proved significantly more robust in the aggressive high-lime environment than did conventional combined glass electrodes. Options for further improving the design of a lime treatment plant are considered.

Utilization of a bioluminescence toxicity assay for optimal design of biological and physicochemical wastewater treatment processes

AbstractA comprehensive laboratory investigation was conducted to test the feasibility of employing biological and physicochemical treatment processes for complex wastewaters discharged by several chemical industries. Results obtained during this study indicated that the wastes contain a fraction of toxic and nonbiodegradable organic matter, which limits the implementation of a conventional biological treatment process for the combined wastewater stream.Toxicity, as measured by a bioluminescence assay (Microtox), served as a valuable tool to assess biological treatability of various waste sources, with the aim to select an economically feasible and environmentally acceptable treatment/management program for an industrial park. Toxicity values served as quantitative indices for the establishment of baseline data of removability potential, defined either by biodegradation or carbon adsorption. This removability data enabled identification of problematic waste sources, which are only partially biodegradable and/or possess considerable toxicity.Further investigation of the problematic waste streams focused on the evaluation of activated carbon adsorption characteristics, using toxicity balances instead of traditional chemical determinations. This method could be successfully employed to yield simultaneously both adsorption characteristics and an assessment of the impact of the treated effluent on biota in receiving waters. © 1994 by John Wiley & Sons, Inc..

Physicochemical Treatment of Tropical Wastewaters: Production of Microbiologically Safe Effluents for Unrestricted Crop Irrigation

The objective of this work was to find an alternative wastewater treatment technology to that of waste stabilization ponds which was capable of producing an effluent safe for reuse in irrigation, but which did not require the large land areas of such a system. Single-stage lime treatment of raw domestic wastewater in a continuous-flow pilot-plant produced an effluent suitable for reuse in unrestricted irrigation by attaining the Engelberg/WHO guidelines of ≤ 1 intestinal nematode egg per litre and ≤ 1000 faecal coliforms per 100 ml. Such treatment was achieved for a mean hydraulic retention time in the sedimentation tank of less than nine hours. The principal mechanism of bacterial removal was physical entrapment and sedimentation to the sludge layer: high pH was only a secondary mechanism for faecal coliform destruction. Faecal coliforms acted as good indicators of the removal of salmonellae in the lime flocculation-sedimentation system, but intestinal nematode eggs were not reliable indicators of the removal of protozoan cysts.

Assessing effluent fluoride concentrations following physicochemical wastewater treatment

The anticipated fluoride concentrations in untreated wastewater, as well as their removal during physicochemical treatment, were determined in order to assess potential risks to the aquatic ecosystem of the St. Lawrence River due to proposed fluoridation of Montreal's drinking water. Monitoring of the raw wastewater yielded average daily fluoride concentrations of 0.22–0.58 mg/L, but discrete sample concentrations ranged from 0.20 to 1.11 mg/L. This indicates that significant massive point discharges occur in the Montreal Urban Community (MUC) sewer system. Jar tests suggest that no precipitation of fluoride would occur following ferric chloride and polyelectrolyte addition at doses similar to those used on the full-scale wastewater treatment plant. This is confirmed by thermodynamic analysis of the solubility of various fluoride species. Full-scale tests, conducted by applying a continuous fluoride dose to the plant influent, confirmed that no removal would result from the treatment process. However, the plant did dampen the shock loads of fluoride from industrial sources. The predicted average raw wastewater fluoride concentration, including ground water and unidentified industrial discharges, was calculated to be 0.83 mg/L. Unidentified sources contribute 132 kg/d (~ 40% of the total). The average fluoride flux in the St. Lawrence River, as a result of fluoridation of the drinking water, would increase by 1.2%. Key words: fluoridation, physicochemical wastewater treatment, St. Lawrence River, mass balance analysis.

Biological treatment of pharmaceutical wastewater

A study of physicochemical and biological treatment of pharmaceutical wastewater by the activated sludge process was performed in an oxidation ditch. The physicochemical study using different coagulants revealed that all the coagulants used are not effective and their doses required were very high for COD reduction. In the biological oxidation study, it was found that the wastewater could be processed at all organic loadings and phenol concentrations encountered in wastewater. The yield coefficient and decay coefficient were 0.75 (COD basis) and 0.01 day−1 (COD basis), respectively.

Physico-chemical treatment of municipal wastewater. Coagulation-flocculation

This article traces the possibilities of physico-chemical treatment of domestic sewage with particular attention to coagulation-flocculation processes. As coagulants the following have been used: ferric chloride, hydrated lime and alum. Different types of coagulant aids have been used too. Besides pilot-plant experiments, a large number of batch experiments has been carried out in order to determine the range of optimal doses of coagulants/coagulant aids/pH and so on. The fate of specific organic and inorganic components (proteins, detergents, low organic acids, phosphorus, nitrogen) as well as TOC, BOD and COD in this chemical treatment have been studied. The suspended and most of the colloidal fractions have efficiently been removed. A considerable fraction, which is defined as soluble, has been removed too. The significance of the findings for wastewater treatment processes have been discussed.

Physicochemical treatment of an Australian municipal wastewater

Physicochemical treatment of wastewater from a typical Australian suburb is being investigated in a pilot plant facility near Melbourne, Victoria. Lime-coagulation at high pH, ammonia stripping and activated carbon treatment are being monitored. in various modes. Analyses of diurnal variations in incoming wastewater quality and typical resultant product waters are quoted. Experience has shown that the system can be operated in a simple practical manner to produce a high-quality water suitable for reuse by industry, or for discharge to a critical watercourse. The ease with which the system can be started up or adjusted for varying flow would be of benefit for holiday resorts or for temporary facilities in a rapidly expanding development.

Physico-chemical treatment of strong municipal wastewater

Direct chemical flocculation-clarification of strong new wastewater followed by adsorption on activated carbon has been investigated. The fate of specific organic components (low organic acids, carbohydrates, proteins, fats as well as BOD and COD) in the chemical treatment process was also studied. Excellent removals of phosphates, fats and suspended solids and a clear effluent were obtained in the chemical treatment. The clear ‘primary chemical’ effluent is, however, of high soluble organic content, the largest fraction being the soluble (low) organic acids and carbohydrates. Adsorption of the chemically treated wastewater on activated carbon gave a 60 per cent removal and a final effluent of a relatively high organic content including BOD. The high concentration of remaining organics is ascribed to poor adsorbability of the low organic acids anions on activated carbon. The significance of the findings for process considerations is discussed.