Integration between chemical oxidation and membrane thermophilic biological process

Full scale applications of activated sludge thermophilic aerobic process for treatment of liquid wastes are rare. This experimental work was carried out at a facility, where a thermophilic reactor (1,000m3 volume) is operated. In order to improve the global performance of the plant, it was decided to upgrade it, by means of two membrane filtration units (ultrafiltration –UF-, in place of the final sedimentation, and nanofiltration –NF-). Subsequently, the integration with chemical oxidation (O3 and H2O2/UV processes) was taken into consideration. Studied solutions dealt with oxidation of both the NF effluents (permeate and concentrate). Based on experimental results and economic evaluation, an algorithm was proposed for defining limits of convenience of this process

Monitoring of a pilot GFO filter for removal of low-concentration arsenic in water

Many water treatment plants (WTPs) were designed to remove ammonia, iron, and manganese simultaneously using biofilters. In some cases (especially in the Pianura Padana area, in Italy) such plants were designed without a specific treatment stage for arsenic removal because its concentration in the groundwater (i.e. 10 to 20 µg/L) was lower than the previous maximum contaminant level (MCL) of 50 µg-As/L; therefore, specific treatments for arsenic removal must be introduced or upgraded in WTPs. In this work, the results of a 19-month monitoring campaign are reported for a pilot granular ferric oxide (GFO) filter installed in an Italian WTP as a polishing stage. The aim was to investigate the performance of GFO with low arsenic concentrations. The results show that, if the groundwater arsenic concentration is close to the MCL, GFO treatment can be cost effective (approximately 80,000 bed volumes have been treated). It was confirmed that GFO can be effective for the removal of both As(III) and As(V) species

Reducing the chlorine dioxide demand in final disinfection of drinking water treatment plants using activated carbon

Chlorine dioxide is one of the most widely employed chemicals in the disinfection process of a drinking water treatment plant (DWTP). The aim of this work was to evaluate the influence of the adsorption process with granular activated carbon (GAC) on the chlorine dioxide consumption in final oxidation/disinfection. A first series of tests was performed at the laboratory scale employing water samples collected at the outlet of the DWTP sand filter of Cremona (Italy). The adsorption process in batch conditions with seven different types of GAC was studied. A second series of tests was performed on water samples collected at the outlet of four GAC columns installed at the outlet of the DWTP sand filter. The results showed that the best chlorine dioxide demand (ClO2-D) reduction yields are equal to 60–80% and are achieved in the first 30 min after ClO2 addition, during the first 16 days of the column operation using a mineral, coal-based, mesoporous GAC. Therefore, this carbon removes organic compounds that are more rapidly reactive with ClO2. Moreover, a good correlation was found between the ClO2-D and UV absorbance at wavelength 254 nm using mineral carbons; therefore, the use of a mineral mesoporous GAC is an effective solution to control the high ClO2-D in the disinfection stage of a DWTP

From the application of water safety plan to the achievement of the ISO 22000:2005 standard: A case study

The Water Safety Plan (WSP) model provides a completely new, cross-cutting and multidisciplinary approach for the risk assessment of drinking water pollution. The concept of “control” of the drinking water supply system (DWSS) is replaced by the concept of “under control”, in order to protect human health. The key factor of the WSP approach is the identification and mitigation or, if possible, the elimination of all factors that may cause a chemical, physical, microbial and radiological risk for drinking water. Due to its characteristics, the WSP can be perfectly integrated with the Hazard Analysis Critical Control Points (HACCP) system, a food safety management system which has the same approach of the WSP for the control of CCPs in food and drink production. Based on the Codex Alimentarius indications, 7 main principles have to be followed in order to establish a HACCP plan. These 7 principles are resumed in the International Organization for Standardization (ISO) 22000:2005 management system. The aim of this study is to evaluate how the WSP implemented for the DWSS of Mortara, Italy, was integrated with the HACCP system, in order to achieve the ISO 22000:2005 standard. The novelty of this work is that this is one of the first nationwide application of the ISO 22000:2005 standard on the whole DWSS stages, from catchment to consumer. In this way, all the DWSS criticalities have been detected. Moreover, the drinking water quality control system has been improved so much to consider water by rights a food

Methodological approach for the optimization of drinking water treatment plants’ operation: a case study

Critical barriers to safe and secure drinking water may include sources (e.g. groundwater contamination), treatments (e.g. treatment plants not properly operating) and/or contamination within the distribution system (infrastructure not properly maintained). The performance assessment of these systems, based on monitoring, process parameter control and experimental tests, is a viable tool for the process optimization and water quality control. The aim of this study was to define a procedure for evaluating the performance of full-scale drinking water treatment plants (DWTPs) and for defining optimal solutions for plant upgrading in order to optimize operation. The protocol is composed of four main phases (routine and intensive monitoring programmes – Phases 1 and 2; experimental studies – Phase 3; plant upgrade and optimization – Phase 4). The protocol suggested in this study was tested in a full-scale DWTP placed in the North of Italy (Mortara, Pavia). The results outline some critical aspects of the plant operation and permit the identification of feasible solutions for the DWTP upgrading in order to optimize water treatment operation

Electrolytic Recovery of Nickel and Copper from Acid Pickling Solutions Used to Treat Metal Surfaces

The increased use of heavy metals in process industries often results in the generation of large quantities of wastewater (WW) and aqueous waste (AW) containing mixtures of heavy metals such as copper and nickel. This research focuses on the electrochemical recovery of copper and nickel from acid pickling solutions used to treat metal surfaces. Using hull cells, beaker plating, and electrolytic cells in pilot scale (capacity 30 L), the most important parameters influencing the process have been identified (temperature, contact time, and current density). In total, about 60 tests were carried out on AW containing nickel and copper. The results of the tests carried out with copper-containing AW shows that removal yields are often higher than 50%; while the energy consumption is less than 15 kWh kg −1 of metal deposited. The best removal efficiency (100%) was achieved by applying a current density of 6 A dm −2 and the energy consumption was 2 kWh kg −1 . The tests carried out with AW containing nickel point out very low removal yields (< 20%) and very high energy consumption (even exceeding 300 kWh kg −1 ). The best removal yield obtained, applying a current density of 3 A dm −2 , is 6.7% with an energy consumption of 40 kWh kg −1 of metal removed. A costs analysis based on Metal Exchange value was carried out. The cost analysis suggests that the results, in terms of removal and recovery, obtained for these metals, in particular for copper, are very promising for an industrial application

Enhancing arsenic removal from groundwater at household level with naturally occurring iron

Abstract A supply of drinking water low in Arsenic (As) prevents arsenic poisoning. The presence of high concentrations of iron (Fe) in groundwater under the alluvial plains of the large rivers in Southeast Asia is a prerequisite for the simple removal of As. This study investigated the mechanisms and possibilities for enhancing As removal with naturally occurring Fe in a reliable, low cost and sustainable way. The results of the study show that As removal with Fe is greatly enhanced by the addition of an oxidizing agent (preferably KMnO4) immediately after the pumping of groundwater. Further enhancement of As removal in the presence of Fe can be achieved by adding a small volume of a concentrated basic solution of MnO4- and AlO2-, which has a combined oxidation, coagulation and buffering capacity. Best results were obtained when this solution was mixed with the groundwater immediately after its pumping until a pale pink color appeared. Maximum required reaction time was 10 minutes and subsequent filtration of the water was able to reduce the As concentration to near zero. Concentrations of MnO4- and AlO2- can be varied in the solution to achieve sufficient As removal to suit different Fe/As ratios and the presence of interfering co-occurring anions