M. Lloréns

Nutrient removal and sludge production in the coagulation-flocculation process.

Nutrient removal and sludge production in the coagulation-flocculation process, applied to a slaughterhouse effluent, have been studied. Fe2(SO4)3, Al2(SO4)3 and polyaluminium chloride were used as coagulants. Inorganic products were used as coagulant aids: activated silica, powdered activated carbon and precipitated calcium carbonate and synthetic polyelectrolytes: cationic polyacrylamide, polyacrilic acid, anionic polyacrylamide and polyvinyl alcohol. Performances were measured under optimum conditions for the products used. They were found after studying the different variables which influence the process. Phosphorus removal is very high (approximately 100% for the orthophosphate and between 98.93% and 99.90% for the total phosphorus). Ammonia nitrogen removal is very low although appreciable performances are observed for albuminoid nitrogen (73.9-88.77%). The use of coagulant aids reduces the volume of the sludge produced up to 41.6%.

Microscopic observation of particle reduction in slaughterhouse wastewater by coagulation-flocculation using ferric sulphate as coagulant and different coagulant aids.

A coagulation-flocculation treatment has been applied to a slaughterhouse liquid effluent, using ferric sulphate as coagulant and activated silica, powdered activated carbon, cationic polyacrylamide, polyvinyl alcohol, polyacrylic acid and anionic polyacrylamide as coagulant aids in order to improve the settling time. Once the optimal conditions had been established (speed and time of stirring during flocculation step, pH, coagulant and coagulant aid doses), the efficiency of the coagulation-flocculation process was studied by comparing the particle size distribution before and after the addition of the coagulant. When ferric sulphate was used without the coagulant aids, particle removal efficiency varied with size, although overall efficiency was quite substantial (87%). The use of coagulant aids improved the removal efficiency, except in the case of activated silica, when it fell to 78%. In all other cases removal efficiency values between 93% (for polyvinyl alcohol) and 99% (for anionic polyacrylamide) were reached.

Influence of thermal stratification on the behaviour of a deep wastewater stabilization pond

Abstract Deep lagooning is an alternative to conventional lagooning and it implies smaller land requirements as an additional advantage. Treatment in deep wastewater stabilization ponds is influenced by thermal stratification. The object of this paper is the study, over a 1-yr period (October 1986–December 1987), of the influence of temperature on the behaviour of a treatment unit (an 8 m deep pond) which receives domestic wastewater. For this study, a spatiotemporal follow-up of the natural treatment process has been conducted. The removal efficiencies achieved for the following parameters varied as follows: COD, 71–92%; BOD5, 83–97%; total Kjeldahl nitrogen, 51–98.8%; ammonia nitrogen, 38.8–99.9%; total phosphorus, 42.2–92.9% and orthophosphate, 40–99%. Log reduction of microorganisms varied between 2.0 and 3.0 for total coliforms, 1.1–3.0 for faecal coliforms and 1.7–3.3 for faecal streptococcus. Other physicochemical parameters observed were: temperature, dissolved oxygen, pH, nitrates and nitrites. The continuous flow of wastewater did not hinder the appearance of a marked stratification in spring-summer: an aerobic epilimnetic zone and an anaerobic hypolimnetic one remained clearly differentiated. The evolution of all the parameters observed was similar. In the absence of thermal stratification, the system was found to function in approximately complete mixing conditions, and the value of each parameter was almost constant throughout the water column; nevertheless, the presence of stratification caused a vertical distribution with marked gradients in the thermocline zone.

The crisis of 1847-1848 and the regulation of company accounting in Spain

The Spanish economic crisis of 1847-1848 brought about changes to the regulation of joint stock companies. Following their implication in the financial crisis, rules were introduced which required the inspection of the accounting records of companies and the disclosure of their financial statements. The intention of legislators was to reduce the number of limited companies and offer some protection to creditors and other parties who transacted with them. The new legislation was particularly significant in its effect on the confidentiality of company accounts. This paper explains how the Spanish government overestimated the role played by limited companies in the crisis and reacted by passing strict legislation which, for general companies, was a major break from the Commercial Code of 1829. The paper also explores aspects of the implementation of the statute passed in 1848.

Primary productivity in a deep sewage stabilization Lagoon

Primary productivity and production measurements and their relationship to observed variations in the concentrations of nutrients (N and P), CO2, pH, temperature, dissolved oxygen and solar radiation were studied in an 8 m deep sewage stabilization pond from October 1986 to December 1987. Two types of tests were carried out: short-term and long-term. The latter permitted the transformation of short-term measurements into daily measurements and the obtention of the relationship between the time of day and primary production. The measurement of primary production was performed using the 14C technique. The highest primary productivity values were detected during the spring-summer period, which was characterized by high temperatures and an increased degree of solar radiation. The maximum value was obtained during June (14.38 mg C mg Chl−1 day−1) and was accompanied by: (a) a decrease in the concentration of nutrients (N and P) and CO2, (b) an increase in pH levels and dissolved oxygen concentrations and (c) a significant proliferation of cyanobacteria (which indicated a low organic loading).

La información contable publicada por los bancos de emisión en España a mediados del siglo XIX

RESUMEN En este trabajo estudiamos la revelación de información realizada por los bancos de emisión en los estados contables publicados en la Gaceta de Madrid entre 1848 y 1868. Para ello hemos recopilado un total de 1.715 estados, cuyo análisis nos ha permitido conocer las prácticas de revelación contable llevadas a cabo por estas entidades. Nuestros resultados sugieren que la información publicada presentó, con carácter general, un alto grado de desagregación, y que las variaciones en los patrones de revelación vinieron motivados por el aumento y diversificación de la propia actividad económica de los bancos de emisión.

Sewage Treatment with a Hybrid Constructed Soil Filter

Abstract The overall aim of this research was to apply a hybrid constructed soil filter for sewage treatment. A hybrid constructed soil filter is an ecological process used for decentralized sewage treatment in villages, small towns or scattered residential areas. Sewage is firstly treated by conventional physicochemical or biological treatment and then allowed to infiltrate through aerated unsaturated zone wherein it gets purified through processes such as filtration, adsorption, chemical reaction and biodegradation. This system has demonstrated a consistent capacity to remove organic matter and nitrogen. Experimental results have shown that under hydraulic load rates of 0.22 m3/m2 · h and organic load rates ranging from 47 to 156 g COD/m2 · h, mean removal efficiencies of 89% for COD, 99% for BOD5, 86% for suspended solids and 52% for total nitrogen can be achieved using an hybrid constructed soil filter. Compared to the conventional activated sludge process, this technology has many advantages, such as simple construction, low operation and maintenance costs, as well as a simple operation.