Environmental Technology

Ince, O.; Anderson, G. K.; Kasapgil, B.

doi: 10.1080/09593331608616329pmid: N/A

The effect of changes in the numbers and the composition of the microbial population on the performance of a pilot-scale crossflow ultrafiltration membrane anaerobic contact reactor (CUMAR) system was studied during both start-up and steady-state operation. An initial epifluorescent microscopic examination of the seed sludge taken from a digester of a municipal wastewater treatment plant revealed that the most dominant group was Methanococcus followed by Methanosarcina, short rods, medium rods, filaments and long rods. Changes in the composition of the dominant methanogenic species were observed throughout the operation. Short rod species were found to be the most dominant group at the end of the study followed by medium rods, Methanococcus, Methanosarcina, filaments and long rods. The numbers of both methanogens and non-methanogens were found to have increased 100% and 50% respectively in the digester at the end of the study. Although the proportion of methanogens in total bacteria in the digester gradually increased from 6.8% to 9.5% the numbers of viable methanogens sharply increased, i.e. 50 times, resulting in a 60 fold increase in the metabolic activity of the methanogens. The maximum OLR applied was 28.5 kg COD/m3.d, at which point COD removal efficiencies of approximately 99% in the permeate and over 97% in the digester were achieved showing that the changes in the numbers and the composition of dominant methanogenic species did not have adverse effect on the performance of the CUMAR system.

Glasgow, Larry A.; Liu, Sean X.

doi: 10.1080/09593331608616330pmid: N/A

The efficiency of solid-liquid separation in coagulation -sedimentation processes depends greatly upon the performance of the coagulant with respect to the production of suitable floc properties. When high-molecular weight polymers (that function primarily by bridging between proximate primary particles) are used as coagulant-aids, the dynamic processes of polymer adsorption and macromolecular rearrangement figure prominently in the success of floc formation. Ideally, one would like to have the macromolecule adsorb quickly upon the primary particle surface in an extended, rod-like conformation; this configuration should persist throughout the collisional process to produce rapid floc growth. A period of macromolecular relaxation would then ensue, with the formation of additional affiliations between functional groups and surface sites. Recently, there have been speculations that the relative speeds of these processes may not necessarily conform to the common perception that sorption is quick and that the rearrangement of the sorbed macromolecule is fairly slow. These questions are critical with respect to the optimal design of coagulation processes that minimize water treatment plant residuals. It is the purpose of the present work to quantitatively assess the dynamic behavior of polymer coagulant-aids in the flocculation of colloidal kaolin. This has been accomplished through use of an unique settling experiment in which the characteristic time associated with reduction of size of the pendant polymer loops can be determined; in this procedure, macrovideography is used to continuously record floc size, and light obscuration is used to produce phototube output profiles that directly reflect characteristics of both floc growth and the sedimentation process. Additional confirmation of these results was sought with a series of simple filtration experiments.

van Bochove, E.; Couillard, D.; Nolin, M. C.

doi: 10.1080/09593330.1995.9618290pmid: N/A

Microbial composting stages were characterized by a multivariate analysis, a global approach instead of a classical univariate analysis of correlations, as part of a study of the organic nitrogen reorganization during a cow manure composting process. Two adiabatic composters were sampled at thirteen intervals during composting and nineteen physical, chemical and biological descriptors were retained for numerical analysis. A principal component analysis (PCA) brought out the most probable factors governing sample distribution. The first three axes of the PCA represented 71% of the total cumulated variance. Sample distribution was along three gradients: organic matter degradation, slow hydrolysable nitrogen, microbial activity. A cluster analysis by average linkage for each composter created five groups of days which are approximately the same size. The interpretation of these groups in terms of the evolution of the microbial composting stages utilized the superposition of clusters onto the first three axes of the PCA. Finaly, the organic nitrogen reorganization was interpreted in relation to the microbial stages characterized by the multivariate analysis.

Bouhamra, Walid S.; Elkilani, Amal

doi: 10.1080/09593331608616332pmid: N/A

The dispersion and the concentration of cement, urea and ammonium sulfate particulates in Shuaiba industrial area in Kuwait were estimated using the “super stack” model. The model, which was described elsewhere (5,8), has been modified to compute solid pollutant concentrations emitted from multiple sources of different heights and emission rates in a simple terrain. The results of the model were compared to data experimentally obtained from different monitoring stations located at distance of 100 to 200 m from the source. Close correspondence existed between the data predicted from the model and the experimentally measured values. This model served as a convenient tool to predict the solid pollutant concentration in a more efficient and accurate way. The concentration contour lines of these solids were established. The FB and NMSE values for the model prediction were in the range −0.37 to 0.788 and 0.394 to 1.431 respectively.

Astier, F.; Paquin, J. L.; Mathieu, L.; Morlot, M.; Hartemann, P.

doi: 10.1080/09593330.1995.9618292pmid: N/A

The aim of this study is to determine the influence of the residence time and the concentration of microorganisms (in water and biofilm) upon the appearance and/or the intensification of the musty taste of water. According to the literature, the origin of this musty taste is mainly biological, the saporigeneous microorganisms being actinomycetes, algae or fungi. This study has been carried out in pilot networks which allow the fixation of residence time and the study of biofilm. The results obtained in this study show that: (i) musty taste intensity increases up to 72 hours of residence time then stabilizes between 72 hours and 120 hours: the treated water entering in the pilot networks has an average threshold value of musty taste of 4 and comes close to 50 up to 72 hours residence time, (ii) concentrations of microorganisms in water and biofilm increase as the residence time increases. Microorganisms detected in water are fungi (from 5.102 to 104l−1) and revivifiable aerobic bacteria (from 102 to 2.103 ml−1) while in the biofilm are detected not only fungi (from 10 to 3.102 cm−2) and revivifiable aerobic bacteria (from 105 to 5.105 cm−2) but also actinomycetes (from 0 to 50 cm−2). However, no quantitative relationship between this musty taste and the different kind of microorganisms detected in water or in biofilm could be established. Nevertheless, the biological origin of musty taste remains the most probable but this taste should be related to the metabolic activity of microorganisms rather than to their concentration.

Mirgain, I.; Green, G.; Monteil, H.

doi: 10.1080/09593331608616334pmid: N/A

The potential for aerobic biotransformation of the herbicide atrazine was investigated in groundwater microcosms under laboratory conditions. Fresh groundwater samples were collected from an agricultural area (Southern Alsace, France) where corn crops have been cultivated for at least ten years. Water microcosms were incubated at 20°C and the biodegradation of atrazine (2.104 mg l−1) was followed weekly over 180 days. After a lag period of 15 to 44 days, catabolism occurred rapidly and total degradation of the added pesticide occurred in 21 to 70 days depending on the physico-chemical composition of the groundwater. Re-application of the pesticide to a sample revealed an induction phenomenon with an increase in rate of the catabolism and disappearance of the initial lag-phase. A combination of enrichment culture techniques and plating on selective atrazine-agar have permitted the isolation of several aerobic Gram negative bacteria able to biodegrade the herbicide in a mixed culture of two or three species.

Baker, John; Stephenson, Tom; Dard, Stephan; Côté, Pierre

doi: 10.1080/09593331608616335pmid: N/A

The formation of a membrane fouling layer was monitored and characterised during treatment of a polluted surface water to potable standard using spirally wound nanofiltration membranes. These were housed in a low pressure reverse osmosis system (6 bar, 5 elements in series) operated at 80% recovery through concentrate recirculation. The plant feed was not disinfected and displayed a high fouling tendency. Normalised product flows of the membranes decreased to about 50% of its initial value during a period lasting from 8 – 38 days after which flux stabilisation occurred. Membranes operated intermittently stabilised more quickly after 8 – 16 days. Salt rejection and membrane feed channel differential pressure were found to display no trend as a result of fouling of these membranes. Destructive membrane analysis revealed significant fouling even after short periods of operation (14 days). Initial deposits of foulant were found to accumulate alongside the membrane feed channel spacer and with time these deposits encroached upon the remaining free membrane area. The fouling layer was a mixture of biological, organic and inorganic species. Calcium and phosphorus were the main inorganic components present with minor iron and aluminium. The high levels of phosphorus found were probably due to the use of sodium hexametaphosphate as a pretreatment.

Uemura, Shigeki; Tseng, I-Cheng; Harada, Hideki

doi: 10.1080/09593330.1995.9618295pmid: N/A

A thermophilic (55°C) upflow anaerobic sludge blanket (UASB) reactor was operated by feeding a wastewater containing sucrose at a fixed total organic carbon (TOC) loading rate of 18 kg TOC m−3 d−1 for a period of 3 years. After this operation period, the reactor temperature was shifted from 55°C to 65°C to investigate the effect of this temperature elevation both on reactor performance and on the characteristics of thermophilic granular sludge. A sharp increase in the effluent TOC occurred after the temperature shift, leading to a deterioration of TOC removal from 90% to 65%. Methane production from the reactor gradually increased from 100 to 130 l d−1 during the first 40 days of 65°C operation, and then drastically decreased to 40–50 l d−1. This process failure was attributed to the disintegration of the granular sludge during 65°C operation. Microbial characteristics of the granular sludge were evaluated before and after the temperature shift. The acetate-utilizing and propionate-utilizing methanogenic activities remained unchanged after the temperature shift while the H2-utilizing methanogenic activity in 65°C operation was slightly higher than that for 55°C operation. No remarkable change was found in the numbers of acetate-utilizing, H2-utilizing and propionate-utilizing groups in both temperature periods.

Tutarli, A.; Cici, M.; Çelik, S.

doi: 10.1080/09593331608616337pmid: N/A

In this study, operating parameters of the gas chromatograph are described for the determination of trifluralin and chloridazon in the soil. Average recoveries of these pesticides from previously-untreated soil were 85 % for trifluralin and 89 % for chloridazon fortified at 2 mg/40 g soil and 0.2 mg/40 g soil levels. Trifluralin and chloridazon were sprayed uniformly by aerial application on two small field plots (each 250 m2) containing agricultural land that had never been treated with pesticide. Soil samples collected from these field plots at certain time periods and depths were analysed by Gas Chromatography (GC). The results of analysed soil samples within a 6-months period ranged from 6.0–0.2 mg/kg and 2.9–0.7 mg/kg for chloridazon, 7.1–1.5 mg/kg and 1.5–0.1 mg/kg for trifluralin at 0–5 cm and 15–20 cm depths, respectively. The residues of these pesticides were also investigated in agricultural lands in Elazig. The amount of trifluralin was found under the detection limits of GC. The other results indicate that residues of chloridazon are available and very important in the soil. In addition, the effects of volatilization and ultraviolet radiation (254 nm) were studied on the pure forms of trifluralin and chloridazon. The importance of each of these parameters on the disappearence rates of herbicides was determined separately by keeping herbicide at two different controlled temperatures (30 °C and room temperature) and exposing to UV light for 15 days.