Daniel Prats

Removal of anionic and nonionic surfactants in a wastewater treatment plant with anaerobic digestion: a comparative study

This paper presents a comparative study of the elimination of anionic surfactants (linear alkylbenzene sulphonates, LAS) and nonionic surfactants in a conventional municipal activated sludge plant. The LAS were analysed by high performance liquid chromatography, after extraction and purification. The nonionic surfactants was analysed by the Wickbold method. The elimination of the surfactants in water, suspended solids and sludges were determined in the different stages of the purification process. The results obtained show that over 90% of the surfactants were eliminated. The maximum degradation took place in the aeration tank.

Polychlorinated biphenyls and organochlorine pesticides in marine sediments and seawater along the coast of Alicante, Spain

Abstract In this paper we present the results obtained in a sampling programme carried out from 1989–1990, whose aim was to study the presence of organochlorine compounds in marine sediments and seawater along the coast of Alicante, Spain. There have been identified DDTs, HCHs, HCB, cyclodienic pesticides and derivatives and PCBs (Aroclor type commercial mixtures and selected PCB congeners). The analytical method consists of 3 phases, i.e. extraction, cleanup and analysis through capillary gas chromatography with electron capture detection. The amount of material used for extraction was 1 kg of sediment samples and 50 l of seawater samples. The levels of organochlorines in sediments are low. Concentration ranges were as follows: PCB total, 0.05–9.69 ng g −1 , sum of DDTs, 0.01–0.3 ng g −1 , Hexachlorobenzene (HCB), 0.01–0.12 ng g −1 , and smaller values for other compounds. In the dissolved phase of seawater there were identified HCHs in concentrations ranging from 1.3–2 ng l −1 .

Las monitoring in a lagoon treatment plant

Abstract The purpose of the study was the monitoring of Linear Alkylbenzene Sulfonate (LAS) and its biodegradation intermediates, Sulphophenyl Carboxylates (SPC) as well as other operating parameters in the treatment plant of Guardamar de Segura (Alicante, Spain) during a period of two years. This plant uses a lagoon type system on which very little information has been published regarding surfactant removal. The ponds are usually designed as a function of the organic load-Biological Oxygen Demand (BOD 5 ) to be treated and they are currently located in communities not larger than 50,000 inhabitants. Both LAS and SPCs have been monitored using specific analytical techniques. BOD removal in the treatment plant monitored was nearly 90% which justifies this type of system for small communities. Total LAS removal was very high, >97% and it was found that the largest part of the removal was due to biodegradation (>83%) with almost total mineralization.

Modeling eutrophication kinetics in reservoir microcosms

Abstract This study addresses the question of how a general seasonal eutrophication model, WASP5, can handle daily phytoplankton and nutrient dynamics in perturbed microcosms for 1- to 2-week periods of time. It is intended to explore both the interpretative and the predictive capabilities of conventional kinetic formulations. The general method adopted in this study is to first apply EUTRO5, a component of WASP5, to a well-behaved microcosm, calibrating the parameter values and reformulating equations if necessary. Next, the calibrated model is subjected to testing in other microcosm experiments, with altered parameter values if necessary. Model performance is further explored through sensitivity analyses to try to “explain” the observed kinetics in the experiments, and a two-way ANOVA is finally applied to the simulated vs observed evolution curves of the three main variables, i.e. chlorophyll a, soluble-P and ammonia-N in all experiments and microcosms studied.

MBR performance: Operational problems in industry

A major study undertaken by a number of institutions and a leading engineering consultancy has investigated factors affecting the performance in operation of membrane bioreactors in a variety of different industrial applications. Jose Antonio Gil summarises the findings.

Stability of kinetic models from waste stabilization ponds

Abstract This paper studies the effect of small variations in the value of various parameters on solutions at steady-state in a kinetic model for wastewater stabilization ponds. An analytic method of study is developed together with a function of evaluation whose value provides a measure for stabilizing the results. It was found that the stability of the solutions depends on the mean residence time considered, as this is different for each variable or parameter. This procedure may be applied to any kinetic model which simulates the behavior of a biochemical reactor.

Effects of Linear Alkylbenzene Sulfonates (LASs) in Sewage Sludge–Amended Soils on Nutrient Contents of Broccoli Plants

Abstract Sewage sludge is used in agriculture as a fertilizer and an organic amendment to improve physical and chemical soil properties. However, sludge contains organic compounds, such as surfactants, which may be toxic in the soil–plant system. The effects on plants of linear alkylbenzene sulfonates (LAS), a group of anionic surfactants that are widely used in detergent products, have not been well defined. In this experiment, the effect of differently treated sewage sludge containing LAS on the macronutrient and sodium contents of different parts of broccoli plants (Brassica oleracea L. var. botrytis subvar. cymosa Lam.) was studied in a field experiment. Fertilizer treatments were un‐composted sewage sludge (UCSS), composted sewage sludge (CSS), and a control without fertilization (NF). The LAS levels were established across all fertilizer treatments by addition of 0, 15, or 30 g LAS m−2 (LAS0, LAS15, and LAS30, respectively). In general, the macronutrient contents in shoots, leaves, and edible parts of broccoli were higher in plants cultivated without fertilization but with LAS. In most cases, the LAS application increased the nitrogen, phosphorus, and sodium contents of the different plant parts, whereas calcium and magnesium concentrations were reduced.

Quaternary liquid-liquid equilibrium: water-acetic acid-2-butanone-cyclohexane at 25°C

Abstract Mutual solubility and tie line data at 25°C, and atmospheric pressure are presented for the quaternary system wateracetic acid-2-butanonecyclohexane. The system contains two pairs of partly miscible compounds with very different solubilities which produce a solubility surface with a large hump and tie lines which do not lie on tie line planes. The UNIQUAC equation is used to correlate the liquid-liquid equilibrium data.

Evaluation of the methods of correlation and interpolation of quaternary liquid-liquid equilibrium data. Application to the system water-ethanol-chloroform-toluene at 25°C

Abstract Ruiz, F., Prats, D. and Gomis, V., 1986. Evaluation of the methods of correlation and interpolation of quaternary liquid—liquid equilibrium data. Application to the system water—ethanol—chloroform—toluene at 25°C. Fluid Phase Equilibria , 25: 147-160. The advantages and disadvantages of three ways to correlate and interpolate quaternary liquid—liquid equilibrium data: (1) the graphical methods, (2) the analytical methods using models describing the mixture Gibbs energy and (3) the analytical methods using models for the equilibrium ratios, are studied. To carry out this objective, firstly, data published previously for the system water—ethanol—chloroform—toluene at 25°C are correlated using the three different methods; then, a new set of tie line data for the same system are determined experimentally; finally, these experimental tie lines are compared with the interpolated ones from the three correlations, and the accuracy of each one is checked.

Forecasting Water Demand in Residential, Commercial, and Industrial Zones in Bogotá, Colombia, Using Least-Squares Support Vector Machines

The Colombian capital, Bogota, has undergone massive growth in a short period of time. Naturally, this growth has increased the city’s water demand. The prediction of this demand will help understand and analyze consumption behavior, thereby allowing for effective management of the urban water cycle. This paper uses the Least-Squares Support Vector Machines (LS-SVM) model for forecasting residential, industrial, and commercial water demand in the city of Bogota. The parameters involved in this study include the following: monthly water demand, number of users, and total water consumption bills (price) for the three studied uses. Results provide evidence of the model’s accuracy, producing between 0.8 and 0.98, with an error percentage under 12%.