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Petrochemicals are chemicals which are derived from petroleum, and these products include organic as well as inorganic chemicals. In the petrochemical industry, the wastewater may contain high amounts of oil which are released in the wastewater during several processes.
This section provides details on the latest developments and efforts in the petrochemical industry waste water treatment.
We have discussed the following:
- Current Wastewater Treatment Process - Petrochemical Industry
- New technologies in the Petrochemical Industry Waste Water Treatment
- Petrochemical Wastewater Treatment by Means of Clean Electrochemical Technologies
- Enhanced Biodegradation of Petrochemical Wastewater Using Ozonation And BAC Advanced Treatment System
- Sulfide Removal In Wastewater from Petrochemical Industries By Autotrophic Denitrification
- Overview of the Application of Anaerobic Treatment to Chemical and Petrochemical Wastewaters
- Observer-Based Time-Optimal Control of an Aerobic SBR for Chemical and Petrochemical Wastewater Treatment
- Transformation of Dimethyl Phthalate, Dimethyl Isophthalate and Dimethyl Terephthalate by Rhodococcus Rubber Sa And Modeling the Processes Using the Modified Gompertz Model
- The Use of Treatment Wetlands for Petroleum Industry Effluents
Current Wastewater Treatment Process - Petrochemical Industry
The current wastewater treatment method includes collection allowing different streams to be collected separately, routing, and treatment. Dependent of the degree of the (required) treatment the following steps are distinguished:
- Primary treatment (API/CPI/PPIseparator, sour water strippers, buffer tanks)
- Secondary treatment (coagulation flocculation-flotation, biological treatment)
- Tertiary treatment (sand-filtration, membrane-filtration, chemical oxidation)
Pollution Characteristics of Petrochemical Waste
A typical petrochemical wastewater treatment plant contains an influent stream that receives feed into the system. After the solids are removed by a mechanical separation, the next few stages, comprising automatic and flotation oil sucking processes, remove the oil to an oil storage tank. Water, from which oil has been removed, flows into an anaerobic system where it is treated by microorganisms in the absence of air. The treated water enters the aerobic treatment stage, where the contents are aerated by the bubbling of air. The flocs that created are collected in sedimentation tanks, generally referred to as Secondary Sedimentation Tanks. The flocs are large enough to settle to the bottom of coagulation tanks as sludge. The sludge removed by the scroll is dewatered and compacted. The dewatered sludge can either be dumped, dried or incinerated. The high quality permeate stream is finally discharged for reuse.
A Complete Effluent Treatment Plant Includes Facilities For Air And Odor Treatment And Sludge Disposal.
New technologies in the Petrochemical Industry Waste Water Treatment
Petrochemical Wastewater Treatment by Means of Clean Electrochemical Technologies
The removal of chemical oxygen demand (COD), turbidity, phenol, hydrocarbon and grease from petrochemical wastewater (PCWW) was experimentally done by using electroflotation (EF) and electrocoagulation (EC). In the EF unit, a graphite anode and a stainless steel mesh as cathode were used. In the EC unit, iron and aluminium were used simultaneously as materials for two blocks of alternating electrodes. The reactor voltage was 12 V, current density (CD) was varied from 5 to 15 mA cm2, and the residence time varied in the limits of 220 min for EF and 110 min for EC. The results have shown that EC removes the mentioned contaminants from PCWW more effectively than EF. Turbidity removal in the process of PCWW purification was estimated as 83% for EF and 88% for EC. The yields of phenol, hydrocarbon and grease removal by EC were examined under different values of residence time, CD, and with iron and aluminium as materials for electrodes.1
Enhanced Biodegradation of Petrochemical Wastewater Using Ozonation and Bac Advanced Treatment System
The characteristics of degradation/conversion of bio-refractory and the growth of a biofilm are investigated in laboratory-scale pre-ozonation and lifted moving-bed biological activated carbon (BAC) advanced treatment processes treating phenol, benzoic acid, aminobenzoic acid and petrochemical industry wastewater which contains acrylonitrile butadiene styrene (ABS). The optimal reaction time and ozone dosage of pre-ozonation for bio-refractory conversion were determined to be 30 min and 100200 mg O3/hr, respectively. After pre-ozonation of 30 min treatment, BOD5/COD ratio of influent and effluent increased apparently from 20 to 35%, approximately. However, the change of pH in pre-ozonation was inconspicuous. The optimal flow rate of influent and air were controlled at 1.6 l/h and 120150 nl/min in lifted moving-bed BAC advanced treatment reactor. A COD removal efficiency of 8595% and 7090% may be maintained by using an organic loading of 3.26.3 kg COD/m3 day and 0.61.6 kg-COD/m3 day with an HRT of 6.0 h as secondary and advanced treatment system, respectively. The time required for the BAC bed is be regenerated by a thermal regeneration is prolonged 45 times more than that of GAC system. It can be estimated that the enhanced COD removal capability of the biofilm was not only due to the increase in the COD removal capability of acclimated bacteria, but also due to species succession of bacteria in bio-film ecosystem.2
Sulfide Removal in Wastewater from Petrochemical Industries by Autotrophic Denitrification
An alternative flowchart for the biological removal of hydrogen sulfide from oil-refining wastewater is presented; autotrophic denitrification in a multi-stage treatment plant was utilized. A pilot-scale plant was fed with a mixture of the following constituents: (a) original wastewater from an oil refining industry (b), the effluent of the existing nitrification-stage treatment plant and (c) sulfide in the form of Na2S. Anoxic sulfide to sulfate oxidation, with nitrate as a terminal electron acceptor, proved very successful, as incoming concentrations of 110 mg S2−/L were totally converted to SO42−. At complete denitrification, the concentration of S2− in the reactor effluent was less than 0.1 mg/L. Fluctuating S2− concentration in the feed could be tolerated without any problems, as the accumulated sulfide in the effluent of the denitrification stage is oxidized aerobically in a subsequent activated-sludge treatment stage. This alternative new treatment scheme was further introduced at the refinery's wastewater processing plant. Thus, complete H2S removal is now accomplished by the combination of the proposed biological method and the existing stripping with CO2. As a result, stripping, and thus its cost, is reduced by 70%.3
Overview of the Application of Anaerobic Treatment to Chemical and Petrochemical Wastewaters
During the last 20 years, as a result of its low cost, anaerobic digestion has turned into a popular wastewater treatment technology. Today, with at least 1330 reactors constructed in the world, it is considered to have reached technological maturity. Until recently however, it was used quite exclusively for the treatment of food industry effluents. It is only during the last 10 years that anaerobic digestion has started to be applied massively to the treatment of sewage and effluents from other industrial activities. During the 1970s and 1980s, the chemical and petrochemical industries were almost refractory to the introduction of anaerobic digestion. The situation has reversed since 1990 and at least 80 full-scale anaerobic plants are nowadays treating this type of waste. Nevertheless, a great amount of promotion is still required before anaerobic digestion can be considered as an accepted technology by this industry. The paper presents the actual situation of anaerobic treatment at full-scale in this industrial sector as well as recent developments at lab-scale and discusses some important concepts to consider before the implementation of an anaerobic treatment. In particular a table is presented with the main characteristics of 65 of the 80 full-scale plants identified to date. The probable reasons for the slow initial development of anaerobic treatment are also discussed and it is shown that anaerobic digestion has been the solution to treatment problems for which aerobic systems were inefficient.4
Observer-based Time-optimal Control of an Aerobic SBR for Chemical and Petrochemical Wastewater Treatment
The present study implements a time-optimal control strategy for a discontinuous aerobic bioreactor, used to treat highly concentrated toxic wastewater present in some effluents of the chemical and petrochemical industries, using respirometric techniques. The control strategy regulates the feed rate to maintain a constant optimal substrate concentration in the reactor, which in turn minimizes the reaction time. Since this control requires on-line knowledge of unmeasurable variables, an Extended Kalman Filter is used as a nonlinear observer. The experimental setup was a 7 litre laboratory Bioreactor used to treat synthetic wastewater with high concentrations of 4-chlorophenol. The controller consisted of a personal computer with data acquisition hardware and real-time software tools, peristaltic pumps and an electronic oxygen meter. Three experiments were performed: one to obtain parameters and calibrate the observer, another one to validate the time-optimal strategy and a final one to evaluate the performance of a fully automated time-optimal operation. When well calibrated, the observer provided good enough estimates and the controller worked as expected, reducing reaction time and increasing the overall efficiency of the bioreactor, when compared with the usual SBR-type operation. 5
Transformation of Dimethyl Phthalate, Dimethyl Isophthalate and Dimethyl Terephthalate by Rhodococcus Rubber Sa and Modeling the Processes Using the Modified Gompertz Model
Phthalate ester isomers, including dimethyl phthalate (DMP), dimethyl isophthalate (DMI) and dimethyl terephthalate (DMT), were found to be transformed by Rhodococcus rubber Sa isolated from a mangrove sediment using DMT as a carbon source initially. At a concentration of 80 mg l−1, transformation of DMP, DMI and DMT was achieved in 9, 1 and 5 days, respectively. During the hydrolytical transformation of DMP, DMI and DMT, their corresponding intermediates were identified as mono-methyl phthalate (MMP), mono-methyl isophthalate (MMI) and mono-methyl terephthalate (MMT), suggesting that transformation of all three isomers followed an identical biochemical pathway of de-esterification. However, none of the produced monoesters was further transformed by R. rubber Sa and they accumulated in the culture media during incubation. It seems that further transformation of monoesters require a set of hydrolytic enzymes different from those involved in the first transformation reaction. Kinetics of DMT, DMI and DMP transformation was well described by the modified Gompertz model independent of the individual substrate condition or a mixture of the three isomers. Both DMI and DMT were easier transformed substrates than DMP, resulting in higher maximum transformation rate (Rm) and shorter lag time phase (λ) derived from the modified Gompertz model. The modified Gompertz model based on one-substrate system can be used in fitting transformation kinetics of mixture substrate system. Our data suggest that degradation of phthalate diesters involves different enzymes in the hydrolysis of the two identical ester groups. 6
The Use of Treatment Wetlands for Petroleum Industry Effluents
Although the use of treatment wetlands is well established for wastewater categories such as municipal waste, stormwater, and acid mine drainage water, their use in treating a variety of industrial and agricultural wastewaters is less well developed. Several large-scale wetland projects currently exist at oil refineries, and numerous pilot studies of constructed treatment wetlands have been conducted at terminals, gas and oil extraction and pumping stations, and refineries. This paper reviews treatment wetland performance for chemical oxygen demand, biochemical oxygen demand, trace organics, metals, toxicity, total suspended solids, nitrogen, and phosphorus. All of these contaminants can be reliably removed from wastewater by treatment wetlands. Pollutant removal is highly dependent on hydraulic loading and influent concentration and to a lesser extent on internal plant communities, water depth, and hydraulic efficiency. In most cases, data from petroleum industry wetland studies indicate that treatment wetlands are equally or more effective at removing pollutants from petroleum industry wastewaters than from other types of wastewater. Until industry-specific data are more complete, this finding can be used along with published rate constants from other wastewater categories to provide conservative estimates for sizing petroleum industry treatment wetlands. 7
1Dimoglo, H. Y. Akbulut, F. Cihan and M. Karpuzcu, 2004. Petrochemical Wastewater Treatment by means of clean electrochemical technologies. Clean Technologies and Environmental Policy, Volume 6.
2Chi-Kang Lin, Tsung-Yueh Tsai, Jiunn-Ching Liu and Mei-Chih Chen, 2001. Water Research 35 (699).
3Eleni Vaiopoulou, Paris Melidis and Alexander Aivasidis, 2005. Sulfide removal in wastewater from petrochemical industries by autotrophic denitrification. Water Research, 39 (4101- 4109)
4Macarie H, 2005. Overview of the application of anaerobic treatment to chemical and petrochemical wastewaters. Water science and technology 42 (201- 213).
5Vargas A, Soto G, Moreno J, Buitron G, 2000. Observer-based time-optimal control of an aerobic SBR for chemical and petrochemical wastewater treatment. Water science and technology, 42 (163- 170).
6Jiaxi Lia, Ji-Dong Gua, b, c, , and Li Panb, 2005. Transformation of dimethyl phthalate, dimethyl isophthalate and dimethyl terephthalate by Rhodococcus rubber Sa and modeling the processes using the modified Gompertz model. International Biodeterioration & Biodegradation, 55 (223-232).
7Robert L. Knight, Robert H. Kadlec, Harry M. Ohlendorf, 1999. The Use of Treatment Wetlands for Petroleum Industry Effluents. Environ. Sci. Technol.,33 (7), pp 973980.