Performances of Reverse Osmosis Membranes for Treatment of Olive Mill Wastewater

In the following study, two methods were employed in which olive mill wastewaters were treated by using reverse osmosis membranes (BW30 and XLE). In the first, wastewater was centrifuged and then passed through the reverse osmosis whereas in the second, an ultrafiltration was placed between the centrifuge and the reverse osmosis. The reverse osmosis experiments were conducted under 10, 15, 20, and 25 bar. The chemical oxygen demand (COD) removal efficiencies under 25 bar were found to be 97.5% for both BW30 and XLE membranes. The highest conductivity removal rates obtained under 25 bar for BW30 and XLE membranes were found to be 95.6 and 96.2%, respectively. As for the highest permeation flux values obtained under 25 bar, they were separately determined for BW30 and XLE as 15.3 and 21.2 L m^?2 h^?1, respectively. The performances of the membranes were also evaluated in terms of their mass transfer coefficients. According to this, all mass transfer coefficients were found to be <1 and also in proximate to one another; this clearly reflects the results as COD and conductivity removals were approximate and there was a lack of any significant difference, whether ultrafiltration was applied or not.     

Typology of Municipal Wastewater Treatment Technologies in Latin America

This paper presents an analysis of the wastewater treatment plants in six Latin American and Caribbean countries. Based on a sample of 2734 municipal treatment facilities, the applied processes are classified by sizes (influent flow) and type of technologies. The distribution of the technologies is also presented for each of the six countries. In addition, a representative municipal wastewater characterization, based on influent data from 174 treatment plants, is proposed. Results show that stabilization ponds, activated sludge, and the upflow anaerobic sludge blanket reactors represent 80% of the treatment facilities of the sample, providing treatment to 81% of the total flow considered. Moreover, 67% of the plants in the sample are small (flow <25 L/s) and the very small facilities (influent flow <5 L/s) are extensively applied in the region (34% of the sample), especially in Mexico and Brazil. The use of very small treatment plants may result in low energy efficiency systems and on possible incompliance of the discharge standards. This common practice in several countries in Latin America should be revised in order to improve the environmental performance of such facilities.     

Interval‐Based Diagnosis of Biological Systems – a Powerful Tool for Highly Uncertain Anaerobic Digestion Processes

Anaerobic digestion (AD) is a highly nonlinear time‐varying process commonly used for biological wastewater treatment, which is subject to large disturbances of both influent concentrations, and flow rates that may lead the process to a breakdown. In order to compensate the effect of these disturbances, the dynamics of the main state variables – including biomass – must be closely monitored and used to improve the process performance. However, AD processes still suffer from a lack of reliable and cheap sensors of key process variables to insure the right process operation. This has led to the development of estimation schemes, which infer the information of such key variables from the available measurements. Nevertheless, reliable measurements are not always possible to get because these readings may be corrupted by noise or erroneous due to sensor failures and as a consequence, they may lead to deteriorated control efforts and the eventual crash of the AD process. In this article, we propose an integrated system for the detection, isolation, and analysis of faults in AD processes by using interval observers (IO). The proposed approach was experimentally implemented on a 1‐m³ pilot scale anaerobic digester. Based on the comparison between the measured outputs and their corresponding estimates, results show that this approach was able to detect sensor failures as well as faults in the basic hypotheses made during the design step.     

Assessing Environmental Impacts of Wastewater Treatment Alternatives for Small‐Scale Communities

The effluents of wastewater treatment plants in small sized communities of less than 2000 population equivalent (PE), which are discharged into sensitive receiving water environments, must receive “appropriate treatment” according to the EU Urban Wastewater Treatment Directive. Appropriate treatment depends on the quality objectives of the receiving waters as well as the relevant provisions of the member states. In this study, wastewater treatment options, such as vegetated land treatment (VLT), constructed wetlands (CW), and activated sludge treatment (AST), by which effluents are discharged to sensitive and less sensitive areas are evaluated by the life cycle assessment (LCA) approach. For this purpose, data related to energy usage, land requirement, raw material consumption, and released emissions from the life phases were collected with an inventory study and the environmental impacts were assessed by using SimaPro 7.1 LCA software. The results obtained from the assessments were compared with each other, which indicated that for small‐scale communities VLT and CW are the most environmentally friendly wastewater treatment option.     

Occurrence of Phthalates in Sewage Sludge from Three Wastewater Treatment Plants in Istanbul,Turkey

Phthalates are considered priority pollutants because of their potential adverse effects on ecosystems and human health. The objectives of this study were to determine the occurrence of five phthalates (DMP, DEP, DBP, BBP, and DEHP) in sewage sludge and to determine the seasonal variability of these contaminants at three (Bahçe?ehir, Pa?aköy, and Tuzla) full‐scale municipal and domestic wastewater treatment plants (WWTP) in Istanbul, Turkey. Mass balance was also calculated for DEHP at Tuzla WWTP sludge treatment units. DMP, DEP, DBP, BBP, and DEHP concentrations in sewage sludge ranged from 1.4 to 2.7 mg/kg dry weight (dw), 1.1 to 2.8, 0.6 to 4.6, 2.8 to 6.2, 18 to 490 mg/kg dw, respectively. Phthalate concentrations from the Bahçe?ehir and Pa?aköy WWTPs met the limit (100 mg/kg dw) of Turkey national sludge regulation and the Europe Union draft of sludge directive for land application, whereas phthalate concentrations from Tuzla WWTP exceeded the maximum permissible concentration. Phthalate concentrations did not show seasonal variations for Bahçe?ehir and Pa?aköy WWTPs, which receive mainly household wastewater while some fluctuations were observed DEP, DBP, and DEHP at Tuzla WWTP which has a lot of industrial wastewater contribution. The mass balance showed that approximately 17% of DEHP in the primary and secondary sludge was removed by anaerobic digestion, while 43% returned back to the beginning of the WWTP and 40% remained in the dewatered sludge. This study suggests that phthalates in sludge from WWTPs with industrial wastewater contribution may limit the use of sludge for land application.     

Performance Evaluation of Constructed Wetlands Treating Wastewater Treatment Plant Effluent in Taihu Lake,China

Constructed wetlands are often used for advanced treatment of the secondary effluent of municipal wastewater treatment plants (WWTPs). Through assessing wetlands based on economic, technical, environmental, and social impacts, an optimal process is selected. In this study, a set of assessment methods for wetland treatment technology is established: The analytic hierarchy process (AHP) is used to establish the evaluation index system; the entropy weight method is employed to calculate the index weights; and the preference ranking organization method for enrichment evaluation (PROMETHEE) is utilized for ranking of the selected treatment technologies. Then four processes applied in Taihu Lake basin, China are evaluated. The results show the following ranking: Vertical‐flow wetland–ecological pond–surface‐flow wetland–horizontal‐flow wetland, vertical‐flow wetland–horizontal‐flow wetland, ecological pond–horizontal‐flow wetland–surface‐flow wetland, and ecological ditch–ecological pond. The wetland exhibits certain universality and space portability with regard to treatment of municipal WWTP effluent. From the view of comprehensive benefits, the ranking of the treatment technology based on the vertical‐flow wetland is high (Φ values between 0.0224 and 0.0349), whereas that based on the ecological pond is low (Φ values between ?0.2086 and ?0.2652), owing to the mechanism of the process itself and the role of microorganisms in the system. Moreover, for organic matter removal, a vertical‐flow wetland process is recommended (48%), whereas for the removal of N contamination, an integrated‐flow wetland process is suggested (31.2% for NH₃‐N, 32.4% for TN removals).     

Using of the Ornamental Fish in Wastewater Biological Treatment

Breeding ornamental fish in wastewater was a successful solution not only to decrease sanitary risks but also to encourage fish growth. In fact, the secondary treated effluent was used to grow a walking catfish (Clarias batrachus), a western mosquitofish (Gambusia affinis; Poeciliidae), and a leopard pleco (Glyptoperichthys gibbiceps). The growth rate of fish reared in final treated wastewater was significantly higher than of treated effluent (25 and 50%) and the relative growth rate during 2 months reached 2, 4, and 2.5, respectively. Bacterial loads were important in the gills compared to other fish organs (intestine, skin, and edible muscles). However, the total aerobic germs ranged between 2 × 10³ and 3.4 × 10³ cfu/g in the edible fish species cultured in secondary treated effluent. The pathogenic bacteria Aeromonas hydrophila was absent in all examined fish muscles. However, the presence of tested fishes did not prevent the reduction of the treatment biological parameter (BOD and COD) at half, in the three treated wastewater proportions (25, 50, and 100%) and thereafter, they clearly participated to the tertiary biological treatment of used water. Further bacteriological and physico‐chemical analyses indicated that the use of treated wastewater in aquaculture is safe and risks to human health are reduced.     

Development of a SPME-GC Method for the Determination of Organic Compounds in Wastewater

A manual SPME method is presented for the analysis of organic compounds in industrial wastewater. 24 compounds commonly found in the wastewater of a chemical plant in northern Germany have been selected as reference compounds. Precision, linearity, and detection limits have been determined. Moreover, the effect of methanol content, pH value, salt content, and an excess of compounds on the extraction process have been studied. Several compounds have been investigated for their applicability as internal standards to quantify the compounds of interest. Since the method will later be transferred to a fully automated SPME-GC system, which will be operated directly on-site at an industrial wastewater purification plant, special attention has been paid to the analysis of real wastewater samples. In this context, the fibre stability has been studied by performing 53 extraction/desorption cycles from one wastewater sample. Neither a decrease in fibre performance nor in precision has been observed indicating that the proposed method is suitable for the analysis of real wastewater.     

Performance Evaluation of a Full‐Scale Extended Aeration System in Al‐Bireh City,Palestine

Major challenges attributed to dysfunctional wastewater treatment facilities in developing countries include lack of commitment and poor informed decision making by the higher municipal administration. This paper presents how process monitoring and control during full scale operation ensures sustainability of civic infrastructures like Al‐Bireh wastewater treatment plant (AWWTP). It is written from the perspective of practical process selection to evaluate the performance of AWWTP, a single‐sludge nitrification–denitrification process with aerobic sludge stabilization. Process monitoring data (July 2000–April 2007) from available monthly operating reports were analyzed and evaluated. Additional data on microbiological analysis and information about facility unit operations were gathered through review of published local literature and interviews with AWWTP personnel. Influent and effluent data evaluated were the chemical oxygen demand (COD), biological oxygen demand (BOD), total nitrogen (TN), and total phosphorus (TP). Despite annual and seasonal variations in AWWTP influent for COD, BOD, TN, and TP, the Palestinian wastewater reuse requirements for restricted irrigation were met. Process design and proper facility operation have direct impacts on effluent quality. The study concludes that regardless of the design capacity and process type, adequate administrative and operational management dictate the sustainability of AWWTP and reuse schemes.