Carbonaceous Pollutants Research Articles

Wastewater quality monitoring

A new concept for monitoring basic water pollution based on a sequential injection analysis system (SIA) provided with two simple spectrophotometric detectors is proposed. The dissolved organic carbonaceous pollution — expressed as TOC (total organic carbon), COD (chemical oxygen demand) or BOD (biological oxygen demand) — and particulate pollution (TSS, total suspended solids) can be estimated using advanced UV spectrophotometry. Moreover, the nitrogenous and phosphorous compounds are determined either directly (nitrate for example) or by addition of a simple reagent, followed by UV-visible detection.

Wastewater Treatment over Sand Columns – Treatment Yields, Localisation of the Biomass and Gas Renewal

Domestic wastewater treatment by infiltration-percolation is a process that is becoming common in France. The aim of this study is to find the depth of biologically active substrate in an infiltration basin by determining the depth of the media colonised by the biomass and by studying oxygen renewal mechanisms. The study using sand columns has allowed simultaneous comparison, on the same profile, of biomass content (ATP), gaseous composition (chromatography) and the variations of the effluent quality (carbon, nitrogen, phosphorus). Down to a depth of 30 cm, removal rates achieved in terms of conventional treatment parameters are very high (COD and SS > 90%, NH4+ ≈ 95%, total phosphorus ≈ 50%). Beyond a depth of 15 cm, the biomass content (expressed in ATP) is ten times less than at the surface, and virtually ceases to develop. Monitoring of O2 levels points to the need for drying periods in order to ensure natural ventilation of the basins. The primary settling stage must be effective in order to avoid any risk of clogging which would prevent the air from being renewed by diffusion.The length of the drying period must be almost double that of the flooding period to allow the media to recover as much of its treatment capacity as possible. This study pinpointed the depth of the biologically active substrate at arround 30 cm. The data obtained from this trial project point to the following design criteria: 1.5 m2/p.e. spread over three basins, and a drying period twice as long as the flooding period. The sand depth will depend on the plant's overall water quality objectives: around 0.50 m for the removal of carbonaceous pollution and nitrification of Kjeldahl nitrogen, a greater depth for disinfection purposes.

The Use of Submerged Structured Packings in Biofilm Reactors for Wastewater Treatment

Structured packings are utilized as biomass carriers in new types of biofilm reactors. These systems have been tested and characterized for a wide range of applications, e.g. carbonaceous and nitrogenous pollution removal of domestic wastewater, purification of industrial effluents, etc. Their efficiency is discussed in terms of eliminated loads and suspended solids retention, as well as with respect to the factors influencing the costs of operation: head loss, backwash frequency, sludge water production. Design considerations of full scale units include both process-related parameters and technological aspects.

Purification of Waste Water from the Paris Conurbation: Biological Removal of Nitrogen at the Valenton Purification Plant

Stage 1 A of the Valenton purification plant, located to the South West of the Paris conurbation, was designed to treat 15 0,00 0 m3/day, which represents pollution of 500,000 population-equivalents. Due to its situation upstream of Paris, the plant was designed primarily with nitrogen removal in mind. The nitrification-denitrification process with an anoxic zone at the plant inlet was selected. This paper looks at results obtained over a three-year period. The results achieve expected levels of elimination of both carbonaceous and nitrogenous pollution. The results achieved in terms of age of the aerated sludge and nitrification kinetics measurements clearly indicate that a nitrification over-capacity exists. However, the denitrification process varies as a function of the concentration levels of organic carbon in the settled water. During periods of rainfall with low BOD5 levels, denitrification is moderately efficient. When the nominal water concentration levels are observed, all the nitrates are reduced in the anoxic zone, and efficiency of the overall nitrogen elimination process reaches 60%. In any case, and particularly in winter, high sludge concentration levels are required to maintain satisfactory kinetics in the nitrification and denitrification stages.

Molecular weight fractionation for the study of complex biodegradation processes

Simulated synthetic sewage was treated in a laboratory-scale, completely mixed, activated sludge plant. Careful control of flow, loading and sludge recycle allowed the plant to be maintained in an essentially steady-state condition for extended periods. “Lumped parameter” determinations were done to assess the plant operating performance in conventional terms. For comparison, more sophisticated determinations were also applied: molecular weight fractionation, amino acids, ammonium-, nitrate- and nitrite-nitrogen, and carbon and nitrogen in the biomass (sludge). Molecular weight fractionation allowed a better characterization of dissolved carbonaceous pollutants. Samples were initially concentrated by low-temperature vacuum evaporation, followed by fractionation by low-pressure gel chromatography. The results demonstrate the value of this method in establishing the fate of complex carbonaceous pollutants present in the feed to biotreaters and in indicating the residual carbonaceous pollutants in the discharge.

Miniature Signals and Miniature Counters: Accuracy Assurance Via Microprocessors and Multiparameter Control Techniques

When14C signals approach background levels, the validity of assumptions concerning Poisson counting statistics and measurement system stability becomes crucial in interpreting the resultant low-level counting observations. This has been demonstrated in our previous work on detection limits for non-Poisson error and it is critical in our current studies of carbonaceous pollutants, where the14C signal from just 5 mg C is comparable to that of the background for our miniature gas proportional counters. To assure data quality, our multi-detector system is designed for the on-line monitoring of critical parameters that reflect both the (statistical) nature of the non-Poisson errors and the underlying (physical) causes. It sends >60 bits of information/pulse to a microprocessor which automatically generates, for each counting period, two-dimensional spectra and multiparameter correlation and control charts. To evaluate the validity of long-term counting of 1–10 mg C we use robust (statistical) estimators, optimal counting interval subdivision, and time series analysis of the individual pulses. New opportunities for selective sampling and chemical fractionation which come with the small sample measurement capability have led us to give special attention also to higher control levels, involving e g, isotonic heterogeneity and representative standard materials.

Mini-Radiocarbon Measurements, Chemical Selectivity, and the Impact of Man on Environmental Pollution and Climate

Underlying principles and results are presented for our program to use isotopic and chemical methods to quantify anthropogenic and natural sources of carbonaceous pollutants. Radiocarbon data have been obtained with a specially-developed miniature low-level gas counting system which has permitted us to assay samples containing as little as 5mg carbon. Measurements of carbonaceous particles, using chemical selectivity and size fractionation to supplement the radiocarbon data, have revealed major impact from both fossil fuel and vegetative (contemporary) sources on urban aerosols. Residential wood-burning has been specifically identified as an important source of respirable particles. Current investigations are directed toward the carbonaceous gases and the application of the accelerator technique for the assay of radiocarbon in individual chemical fractions containing microgram quantities of carbon.