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The aim of this study is to determine physiochemical and bacteriological properties of seawater and sediments from the coast of Tunisia during six successive months. The conductivity was measured using previously calibrated Hach Conductivity meter. Total suspended solid was determined using Whatman GF/C glass fiber filter (Sigma Aldrich), and the turbidity was assessed using a spectrophotometer (UV/Vis). The pH was measured using pH electrodes. Other physiochemical parameters were determined using Pastel UV multiparameter water analyzer (Secomam, aqualabo). Bacterial analysis was displayed by membrane filtration method, and isolates were identified to the species level by Api strips. Susceptibility to antibiotics was determined by disk diffusion methods. Total suspended solid, turbidity, adsorbable organic halogen, chemical oxygen demand, and biochemical oxygen demand were higher than accepted norms in Tunisia. Enterococcus faecalis was detected in all the sites indicating a human fecal contamination, and all the isolates were highly resistant to rifampicin, gentamicin, chloramphenicol, ampicillin, and azithromycin. The situation in Mahdia coast is alarming particularly with the isolation of multidrug resistance strains. It is recommended that the local government provide restrict policies for the treatment and the assessment of municipal wastewater before its discharge into sea. PRACTITIONER POINTS: Coastal Surveillance and Water Quality monitoring in the Rejiche Sea - Tunisia is crucial. Enterococcus faecalis was detected in sea water and sediment samples in the coast of Rejiche. Isolated strains were highly resistant to rifampicin, gentamicin, chloramphenicol, ampicillin and azithromycin.

Textile wastewater purification is a challenging process. Conventional wastewater treatment methods either lack in efficiency, cost-effectiveness or leads to the generation of secondary pollutants. Additionally, some treatment methods are time-consuming. The research presented in the manuscript is a blend of filtration, biosorption, aeration, solar energy-assisted electrolytic precipitation, pH balance, and germicidal treatments with an aim of reducing the suspended solids, intense color, odor, pH, chemical oxygen demand (COD), total dissolved solids (TDS), electrical conductivity (EC), and heavy metal content of textile effluent. Use of environmentally sustainable surface activated biosorbents derived from waste weeds Water Hyacinth (WH) and Parthenium Hysterophorus (PH) as an alternative to commercial grade Activated Charcoal (AC), comparison of adsorption capacities of proposed adsorbents against AC for effluent decolorization, the application of solar energy to run an electrolytic precipitator, and the unique sequential design of various unit processes like coarse and fine filtration, biosorption, aeration, electrolytic precipitation, pH treatment and germicidal UV-C treatment to treat the effluent are some of the novel methodologies explored in the present study. The invented process provides almost completely decolorized (about 90%-94%), particle-free and odorless treated water, with the acceptable levels of heavy metals (Lead-not detected, Arsenic-not detected, Zinc-0.5-0.8 mg/L), TDS (1,500-1,850 mg/L), COD (149-169 mg/L) pH (7.1-7.15), and EC (2.5-2.8 mMhos/cm) as some of the important parameters, fitting well within the standard pollution limits. Performance efficiency estimation and statistical modeling were done for the data using the t test and f test. The values obtained were (t = 2.78 and f = 4.99 for treated WH against AC) and (t = 3.00 and f = 5.38 for treated PH against AC at 0.05 level of significance) as an essential part of the manuscript, proving the supremacy of the proposed process to achieve the standard pollution norms. Cost-effectiveness was an integral factor addressed in the proposed design, recorded a 1.7 USD per 1,000 L of input effluent, which was well below than most of the reported studies. The invented method in the present investigation thus provides an integrated, efficient, eco-friendly, and cost-effective solution to wastewater treatment. PRACTITIONER POINTS: Effluent decolorization is about 68% in comparison with conventional activated carbon. The adsorbent was found to be three times more active than activated carbon. COD value decreased from 2,352 mg/L to about 150 mg/L on treatment with the novel adsorbent.

Both river bank filtration and dead-end sand filtration are becoming increasingly applied in rural areas to improve the quality of fecally contaminated water. To evaluate the capacity of both treatments to remove E. coli, fecal streptococci, and somatic and K13-phages, this study investigates their concentrations in diluted wastewater after short-distance tangential sand filtration and dead-end sand filtration. Bacteria were almost undetectable in both systems after 60 cm depth, and at a pore-water velocity of 1 m/d. Both phages underwent removal of 2.5 logs by tangential filtration, whereas dead-end filtration removed 5.1 logs and 3.9 logs of K13-phages and somatic phages, respectively. After discounting removal by the schmutzdecke, observed only in the dead-end filtration, both systems removed phages similarly. It is concluded that short-distance river bank filtration, alone, does not meet WHO requirements for drinking water. However, the concomitant reduction of suspended solids renders the filtered water amenable to further treatment steps.

Inactivation of Bacillus globigii spores in wash water was studied to simulate chlorine inactivation of Bacillus anthracis spores in water generated during biological cleanups. Eight waters were studied, with six containing detergent. Chlorine levels were approximately 3000 mg/L. Results across different waters showed decreasing inactivation with increasing pH. Inactivation did not appear to be influenced by chemical oxygen demand, suspended solids, turbidity, or dissolved solids. Inactivation efficacy was expressed as the time calculated to yield 6 log10 inactivation at 3000 mg NaOCl/L. This time ranged from 5 to 51 minutes at ~21 °C and from 11 to 209 minutes at ~5 °C. For one wash water, inactivation was conducted when there was no pH adjustment, and when the pH was buffered at 7 and 8. Inactivation in these buffered waters was rapid, but inactivation decreased sharply at a pH above ~9.3.

A novel radial-axial mixer and microbubble ozone reactor for enhancing sludge disintegration was designed. In the batch studies, the new reactor was shown to be significantly effective in improving sludge disintegration and increasing ozone utilization. For ozone dosages of 0.02 to 0.3 gO3/gTSS (total suspended solids) at pH = 10, the average sludge disintegration ratio was more than 17 ± 0.83% higher than that of the conventional reactor. An activated sludge process coupled with discharged sludge ozonated was run for 60 days to evaluate the influence of ozonated sludge feeding on the sludge yield coefficient and effluent quality. Although the effluent chemical oxygen demand (COD) and suspended solids (SS) increased slightly, these values were well below the discharge limit. Furthermore, a sludge reduction efficiency of 95% was attained. The experimental results indicated that the combination of sludge ozonation with the activated sludge process could generate a high quality of effluent and a small sludge yield.

The goal of this study was to establish a modeling tool for river water quality with a direct linkage to the water quality index (WQI5) calculation and the river water quality model, the Water Quality Analysis Simulation Program (WASP), for pollutant transport modeling. The integrated WASP and WQI5 tool was field-tested to assess pollutant loadings and their impacts on river environment. Suspended solid (SS) and electric conductivity (EC) correlation equations and the WQI5 calculation tool were included in the water quality model and direct WQI5 calculation. The SS concentration, which was influenced by river flows, had crucial effects on river water quality and WQI5 values. EC value was controlled by dissolution of soil minerals, which was affected by the watershed drainage area and surface runoff. The integrated system could establish a direct correlation for river water quality, river flow, and WQI5.

This study evaluated the flocculent settling in water and municipal wastewater (MWW) in a 10.6 ft deep column. A total of eight runs at three different testing conditions involving MWW alone, food waste (FW) alone, and FW in MWW (FW+MWW) were conducted. Total suspended solid (TSS), total BOD (TBOD), total COD (TCOD), total nitrogen (TN), and total phosphorous (TP) removal efficiencies after 3 hours of settling were 62%, 46%, 49%, 46% and 62% for FW, and 50%, 43%, 39%, 37% and 24% for MWW. Removal efficiencies of particulate COD (PCOD) and particulate BOD (PBOD) at the lowest surface overflow rate (SOR) of 1.1 m3/m2/hr corresponding to the longest settling time of 3 hours were 59% and 64% for FW, and 65% and 70% for FW with MWW samples. On the other hand, no significant variation between FW and FW with MWW was observed for PN removal after 3 hours of settling.

The first flush of rainwater in urban areas is highly contaminated and causes adverse effects on both the water environment and ecosystem. In this study, a novel filtration device using expanded polypropylene media (EPM) was developed for efficient control of pollutants in first flush of urban runoff. The effect of foaming ratio on EPM for filtration efficiency and clogging potential was examined under various operating conditions. Experimental results using a laboratory-scale filtration device indicated that the removal efficiencies of suspended solids were initially high (>90% removal until 60 minutes) and decreased with filtration time (60% for EPM15 at 180 minutes and less than 10% for EPM45). Similarly, more than 90% of Cr, Pb, and Zn were removed for EPM15 within 30 minutes and decreased with filtration time. The surface area and specific hydraulic resistance of EPM were sensitive to foaming ratio. Optimum conditions for foaming ratio increased pollutant removal and minimized head loss. A simple model was derived and applied for theoretical analysis of the filtration device with EPM.

A pilot-scale study was conducted using electrocoagulation technology to treat chlorine dioxide bleaching-stage effluent of a local pulp mill, with the purpose of evaluating the treatment performance. The operating variables were the current density (0 ~ 133.3 A/m(2)) and hydraulic retention time (HRT, 6.5 ~ 16.25 minutes). Water quality indicators investigated were the conductivity, suspended solids (SS), chemical oxygen demand (COD), true color, and hardness. The results showed that electrocoagulation technology can be used to treat D-stage bleaching effluent for water reuse. Under the operating conditions studied, the removal of conductivity and COD always increased with increases in either the current density or HRT. The highest removals obtained at 133.3 A/m(2) and an HRT of 16.25 minutes for conductivity, SS, COD, true color, and hardness were respectively 44.2, 98.5, 75.0, 85.9, and 36.9% with aluminum electrodes. Iron electrodes were not applicable to the D-stage effluent due to formation of dark-colored ferric complexes.

A program of highway runoff sampling was conducted at four sites in Auckland, New Zealand. Concentrations of suspended solids, particulate copper, and zinc were significantly lower in runoff from a highway paved with a 1-year-old porous friction course (PFC) than in runoff at the other sites. Differences in total metal concentrations were less marked, reflecting relatively high concentrations of dissolved copper and zinc in runoff from the 1-year-old PFC. Runoff quality at a highway site that had been paved with a PFC 6 years previously was similar to that discharged from two impermeable roads, indicating a reduction over time in the quality of runoff discharged from PFCs. Runoff from the highways paved with 1- and 6-year-old PFCs was treated by a grass swale and wet pond, respectively. Both treatments were effective, the former predominantly through the lowering of dissolved metal concentrations and the latter through the lowering of particulate metal concentrations. These results indicate that stormwater treatment can improve the quality of runoff discharged from PFCs, irrespective of their age, provided that treatment is targeted to the predominant contaminant phase present.

Treatment units for stormwater management are being routinely required for new construction and upgrading of older facilities. This paper shows how particle size distribution affects the removal of sedimentation units and how erroneous results are often obtained if one uses simple overall removal efficiency or if the particle size distribution is not considered. Two full-scale devices are used for demonstration. A hydrodynamic device, which generally have low, overall suspended solids removal efficiency, is used for the first case, and it is shown that it actually removes large particles very well but has virtually no removal of small particles. The second case is for a dry detention basin. It is shown that the removal rates are generally in accord with sedimentation theory, removing larger and medium size particles well. Using particle size distribution in evaluating treatment unit performance is a more accurate and precise way of determining the actual performance.

The induced bed reactor (IBR) was developed to apply high-rate anaerobic digestion techniques to high suspended solids substrates (6 to 12% total solids). This technology has been implemented at multiple full-scale installations in the United States and Canada. Residence time distribution studies for 58-L laboratory-scale reactors operated at a 3.8-day hydraulic retention time were conducted at 35, 45, and 55 degrees C under control and active digestion conditions. Rhodamine WT and lithium ion were used as tracers. The results show that the IBR most closely approximated completely stirred tank reactor behavior when operated under the study conditions. Mixing was likely a result of a (1) combination of energy inputs from thermal gradients induced by heat flux through the reactors, and (2) shear induced by gas evolution in the sludge bed.

A circular gravity-phase separator using coalescing medium with cross flow was developed to remove oil and suspended solids from wastewaters. Coalescence medium in the form of inclined plates promotes rising of oil droplets through coalescence and settling of solid particles through coagulation. It exhibits 22.67% higher removal of total suspended solids (TSS) compared to separators without coalescing medium. Moreover, it removed more than 70% of oil compared to conventional American Petroleum Institute separators, which exhibit an average of 33% oil removal. The flowrate required to attain an effluent oil concentration of 10 mg/L (Q(o10)) at different influent oil concentrations (C(io)) can be represented by Q(o10) x 10(-5) = -0.0012C(io) + 0.352. The flowrate required to attain an effluent TSS concentration of 50 mg/L (Q(ss50)) at different influent TSS concentrations (C(iss)) can be represented by Q(ss50) x 10(-5) = 1.0 x 10(6) C(iss)(-2.9576). The smallest removable solid particle size was 4.87 microm.

The activated sludge process is the most common method of secondary municipal wastewater treatment; solids retention time (SRT) is the key control parameter for this process. Typically, operating at long SRT is considered only for nitrification, but there are additional benefits of high SRT operation. This paper presents experimental and literature evidence to demonstrate three major additional benefits of long SRT operation: increased oxygen transfer efficiency; improved biomass particle size distribution, which results in more efficient clarification with fewer effluent particles and suspended solids; and enhanced removal of many emerging contaminants such as pharmaceuticals, personal care products, and endocrine disrupting compounds. This paper presents experimental results from several treatment plants that showed increasing oxygen transfer efficiency and particle size with increasing SRT, and evidence documenting improved removal of emerging contaminants and biodegradable organic carbon. A long-term survey of three treatment plants concludes that operating at higher SRT is not as energy intensive as typically assumed.

A tertiary membrane filtration (TMF) pilot operating on secondary effluent and a membrane bioreactor (MBR) were setup in a side-by-side study as pretreatments for two identical reverse osmosis pilot systems. The water quality of the permeate from both low-pressure membrane pretreatment systems and the fouling rate of the reverse osmosis systems were compared to assess the capabilities of the two low-pressure membrane pretreatments to prevent organic fouling of the reverse osmosis systems. Both pretreatment pilots were setup using typical operating conditions (i.e., solids retention time and mixed-liquor suspended solids). A consistent difference in water quality and reverse osmosis performance was demonstrated during the 12-month study. The MBR permeate consistently had significantly lower total organic carbon (TOC) and chemical oxygen demand concentrations, but higher color and specific UV absorbance compared with the permeate from the TMF pretreatment. The pretreatment with the MBR gave an average reverse osmosis fouling rate over the entire study (0.27 Lmh/bar.month) that was less than half of the value found for the reverse osmosis with TMF pretreatment (0.60 Lmh/bar.month). A correlation of reverse osmosis feed TOC concentration with average reverse osmosis fouling rate also was established, independent of the pretreatment method used. Results from a cleaning analysis, energy dispersive spectroscopy, and fourier transformed infrared reflectometry confirmed that the foulants were primarily organic in nature. It is concluded that, for this type of application and setup, MBR systems present an advantage over tertiary membrane polishing of secondary effluent for reverse osmosis pretreatment.

Temporal evolution of microbiological, physical, and chemical quality of stormwater runoff from a stormwater drain in an urban residential area in Calgary, Canada, was investigated from May to September, 2006 and 2007. Investigating event mean concentrations and their correlations with rainfall characteristics revealed that intensive rainfall events produced highly polluted stormwater runoff when pollutant source limitation did not occur. Inconsistent event-based correlations between total suspended solids (TSS) concentrations and water quality parameters were observed. During storms, the loading of TSS exhibited a flow-dependent nature, whereas microorganism discharge appeared to be governed by a flow-independent mechanism. No strong first-flush effect was observed in either TSS or microorganisms, on average. No correlations of first-flush loads of TSS with rainfall characteristics were identified. Moderate negative correlations between first-flush loads of microorganisms and rainfall depth and intensity indicated that first flush of microorganisms tended to occur in small storms.

Psychrophilic anaerobic digestion recently has been demonstrated as a cost-effective option for the treatment of a range of wastewater categories. In this study, the treatment of alginate production wastewaters was carried out in a pilot-scale expended granular sludge bed (EGSB) reactor. After a 40-day startup with two inocula, a 163-day experiment was run, from moderate to low temperatures, to treat seaweed-based-production wastewater. The results showed that inoculating with the active granular sludge instead of flocculent biomass can remarkably speed up the startup, and, at applied organic loading rates of 1.5 to 3.0 kg chemical oxygen demand (COD)/m3 x d, COD removal efficiencies of 55.4 to 72.6% were achieved. The volatile suspended solids ratio decreased slowly with operation time, as a result of the extremely slow growth rates of microorganisms and the accumulation of inorganic substances. Morphological examination and particle-size distribution of the granules revealed their tendency to disintegrate. Inorganic precipitates, microorganism shift, and substrate limitations may have contributed to it.

A comprehensive study of the dynamics in settling and flocculation properties at a full-scale activated sludge treatment plant with secondary settlers operated at their maximum capacity is presented. An extensive set of process data was analyzed to assess physical parameters affecting the capacity and performance of the secondary settlers. There was a large variation in the settling and compaction properties, and they changed quickly, as a result of the short sludge age. Even though the flocculation properties changed throughout the year, they were generally improved during the summer, with lower values of effluent turbidity and effluent suspended solids concentration. The shear sensitivity, which is a measure of floc stability, was higher during the winter, when the water temperatures were lower. The sludge floc morphology had, in general, a different internal structure, with more round microbial colonies during the warmer summer months and a more net-like open structure during the winter.

Solids in aeration tank effluents contribute to the total organic content and suspended solids concentration, and violates disposal and reuse standards. Therefore, improving the settling properties of sludge helps produce an effluent with a quality that conforms to effluent standards, assuming all other conditions for good settling in the sedimentation tank are favorable. In this paper, seven chemicals that are all cationic polyelectrolytes were tested individually as additives to improve the settling properties of aeration tank effluent from a full-scale wastewater treatment plant. Pilot settling columns designed and constructed at a local wastewater treatment plant were used in this project. Batch settling tests were performed on fresh activated sludge samples that were collected before the secondary sedimentation tank and mixed with different concentrations of the additives without cumulative additions. Each additive was accessed based on its particular sludge settling properties, that is, the shape of the settling curves, the values of the hindered zone settling rate or zone settling velocity, and the stirred sludge volume index. Each additive result was compared with the corresponding properties of a plain sludge sample collected on the same day and used as a control. Substantial and dissimilar improvements were obtained and are presented in the form of graphs and values using 92 settling runs. Shorter lag-times, quicker descending speed of sludge-water interface, higher descending distance, and lower stirred sludge volume indices values were attained with the use of these additives.

A novel circular secondary clarifier was developed to obviate the shortcomings of conventional clarifiers. The novel clarifier provides natural flocculation, which occurs as a result of hydraulic energy dissipation and the formation of sludge cloud referred to as plume. The efficiency of the clarifier depends on the stability of the plume, which in turn depends on the velocity gradient. For natural flocculation to occur, a velocity gradient of 10 to 15 s(-1) was found to be favorable. This velocity also keeps the plume-rise well below the free-surface. The mean particle size of mixed liquor suspended solids increases from 41 to 83 microm in the plume, which indicates agglomeration of particles and confirms that natural flocculation is occurring within the plume. The hydraulic improvement achieved by improving inlet design dissipates hydraulic energy, uniformly distributes flow, minimizes sludge blanket disturbances, and promote flocculation. The improved clarifier operates at 1-h hydraulic retention time.

Regulatory agencies approve automatic samplers containing peristaltic pumps as a sample collection method for stormwater characterization and for treatment-device evaluation. Autosampler performance, as discussed in the limited available literature, can vary across the entire particle size range typically found in stormwater from different source areas and outfalls-reasonably consistent performance for particle sizes250 microm, but much less consistency for particles250 microm. Therefore, a series of experiments was undertaken to quantify the upper range of consistent particle capture that may occur with sampling stormwater suspended sediment and particulate-bound pollutants. These experiments, based on triplicate sampling at each experimental condition, found that peristaltic pump autosamplers commonly used in stormwater monitoring could not repeatedly and effectively capture particles250 microm from a simulated stormwater whose particles have a specific gravity of 2.65. It was expected that the effective size for autosamplers would be correspondingly larger for particles having smaller specific gravities. The height of the sampler had no influence on particle recovery up to a height of 2.5 m, with slightly decreasing recoveries of large particles occurring at greater heights, as a result of reduced sampler intake velocity. Therefore, to characterize the solids across the entire size range and specific gravities that may occur in stormwater runoff, autosamplers should be deployed in conjunction with bedload and floatables sampling.

The double exponential settling model is the widely accepted model for wastewater secondary settling tanks. However, this model does not estimate accurately solids concentrations in the settler underflow stream, mainly because sludge compression and consolidation processes are not considered. In activated sludge systems, accurate estimation of the solids in the underflow stream will facilitate the calibration process and can lead to correct estimates of particularly kinetic parameters related to biomass growth. Using principles of compaction and consolidation, as in soil mechanics, a dynamic model of the sludge consolidation processes taking place in the secondary settling tanks is developed and incorporated to the commonly used double exponential settling model. The modified double exponential model is calibrated and validated using data obtained from a full-scale wastewater treatment plant. Good agreement between predicted and measured data confirmed the validity of the modified model.

To enhance nitrogen removal in an existing microbial contact oxidation (MCO) system with a treatment capacity of 900 m3/d, an upflow multilayer bioreactor (UMBR) was chosen as a preanoxic reactor for the removal of organic matter and nitrate. The removal performance of the retrofitted plant was evaluated during the startup phase at a low temperature in winter. The high removal (>80%) of organic matter and suspended solids in the UMBR provided stable nitrification conditions in the MCO system, as a result of the substantial reduction in organic matter and solids loaded onto the MCO system. This treatment system showed a stable nitrogen removal efficiency of 75.3%, even in the low temperature range 7 to 10 degrees C. Phosphorus was completely removed by chemical precipitation. Production rates of excess sludge, as a function of the loads of influent flowrate and biological oxygen demand (BOD), were 0.022 kg dry solid/m3 wastewater and 0.132 kg dry solid/kg BOD.

This paper presents the study of a mixed porous media composed of expanded perlite and a nonwoven needle-punched geotextile used to reduce the suspended solids load and concentration in urban runoff. Laboratory procedures were designed to quantify the suspended solids removal efficiency and variation in time of filtration rate. Different grain-size distributions of expanded perlite, diverse suspended solids concentrations, and different hydraulic and geometric conditions were tested to determine the most effective filter media. A dimensionless parameter, termed Global Performance Index (GPI), was developed to reach this objective. Measured data were also used to build a dimensional and a regression model to represent the performance of the filter media mathematically. The theory, derivation, and performance of both models are presented and compared with an existent empirical model. The dimensional model better reproduces the observations, becoming a useful tool for the design, operation, and evaluation of commercial porous media filters.

Wastewater treatment facilities use secondary treatment to stabilize the effect of discharged effluent on receiving waters by oxidizing biodegradable organic matter and reducing suspended solids and nutrients. The process was never specifically intended to remove trace quantities of xenobiotics, such as endocrine-disrupting compounds (EDCs) and pharmaceuticals and personal care products (PPCPs). Nevertheless, European studies performed at bench-scale or at small facilities have demonstrated that a critical minimum solids retention time (SRT) can achieve good reduction of many EDCs and pharmaceuticals. The objective of this study was to expand these findings to the removal performance for 20 PPCPs commonly found in the influent to full-scale facilities operating in the United States. The participating plants use SRT conditions ranging from 0.5 to 30 days and include facility capacities ranging from 19 000 m 3 /d (5 mgd) to greater than 1 136 000 m 3 /d (300 mgd). Two pilot membrane bioreactors were also included in the study. The 20 PPCPs were categorized into nine bin combinations of occurrence frequency and treatment reduction performance. While most compounds were well removed, galaxolide (a musk fragrance) occurred frequently and was resistant to removal. A minimum critical SRT, defined as the minimum SRT, needed to consistently demonstrate greater than 80% removal (SRT 80 ), was compound-dependent, with most compounds removed at 5 to 15 days and a small group requiring longer SRTs. From limited data, no additional removal could be attributed to the use of membrane bioreactors, media filters, or longer hydraulic retention times. Reverse osmosis was effective in removing any remaining compounds.

The reduction of organic and nitrogen pollution of wastewater was investigated in two hybrid reactors and compared with the reduction obtained by using a conventional activated sludge reactor (ASR) run as a control. Both HR-1 and HR-2 were activated sludge systems where a low-density carrier, P1 (polyethylene) for HR-1 and P2 (recycled plastics) for HR-2, was added. Firstly, the three reactors were operated at 10 days Suspended Solid Retention Time (SRT(SS)), leading to a complete nitrification. Secondly, the SRT(SS) for each reactor was lowered to 3 days. Nitrification was lost for the ASR but remained complete for HR's. Respirometric techniques were used to measure fixed or suspended biomass activities for heterotrophic and autotrophic biomass. More than 90% of the autotrophic activity was found on the supports whatever the SRT(SS) used. The results may underline the role of the carrier geometry or surface characteristics on the autotrophic/heterotrophic microorganism distribution.

Chitosan, with a degree of deacetylation of 85% and a molecular weight of 2.5 x 10(5) Da, yielding high flocculation efficiency (85 to 100% flocculation) and a broad flocculation region (2 to 45 mg/g suspended solids), was selected for accelerating granulation in a 30-L upflow anaerobic sludge bed (UASB) used to treat wastewater from a tropical fruit-processing industry. Compared with other studies, smaller amounts of chitosan were applied (two injections with 2 mg chitosan/g suspended solids in the reactor at each injection). Comparison with the UASB without chitosan addition, the UASB had a 24 to 37% larger particle size and a 6 to 41% longer solids retention time. In addition, the reactor performances were also enhanced. The UASB with chitosan addition had a 9 to 59% lower effluent chemical oxygen demand (COD), 4 to 10% higher COD removal, up to 35% higher biogas production rate, and a 16 to 68% lower biomass washout. The paired t-test analysis indicated that these performance parameters were significantly different (P < 0.05).

The difference in performance of three differently designed circular secondary clarifiers in the same wastewater treatment plant was analyzed in this paper. Data obtained using flocculated suspended solids and disperse suspended solids tests were analyzed using statistical tools. The conventional clarifier showed more variability in the average effluent suspended solids concentration when compared with the flocculator-clarifiers. Furthermore, a difference in performance among the two different flocculator-clarifiers was found.

This project has two main objectives; the first is to documents the effect of a porous friction course overlay on the quality of highway stormwater runoff, and the second is to assess pollutant removal of a vegetated area along the side of a road from both conventional and porous pavements. The quantity and quality of stormwater runoff from a four-lane divided highway in the Austin, Texas, area was monitored before and after the installation of a porous friction course (PFC). Observed concentrations of suspended solids and pollutants associated with particulate material were much lower in the runoff from the PFC compared with runoff from the conventional asphalt surface. The vegetated highway shoulder reduced the concentrations of many stormwater constituents from the conventional asphalt surface; however, the concentrations of these constituents in runoff produced by the PFC were so low that the vegetated area produced no further reduction in concentration.

Textile plant wastewater being treated in a facultative pond system had too high of a solids concentration to be reused in the dying and rinsing processes. Electrocoagulation was evaluated to further treat the pond effluent to remove turbidity, which was caused by dyes and microorganisms. A range of amperages were tested for removal of turbidity and chemical oxygen demand (COD). Electrocoagulation lowered the turbidity from 1400 NTU to below 50 NTU; and COD was lowered from 550 mg/L to approximately 250 mg/L, which was acceptable for reuse. In addition, a laboratory-scale sedimentation study was conducted on the electrocoagulated pond effluent, which indicated that a settling time of 35 minutes would provide for 80% removal of suspended solids, which was acceptable for reuse of the water in plant processes.

The existing theories incorporated to state-of-the-art, activated-sludge-consensus models indicate that the removal of particulate substrate from the liquid in the activated-sludge process is a two-step process: instantaneous enmeshment of particles and hydrolysis followed by oxidation. However, experimental observations indicate that the removal of particles is not instantaneous and needs a more accurate description. This removal process can actually be described as a three-step process: flocculation, hydrolysis, and oxidation. The principal objective of this research was to observe and model the kinetics of the removal of suspended particles and colloidal particles. A first-order, particulate-removal expression, based on flocculation, accurately described the removal rates for supernatant suspended solids and colloidal chemical oxygen demand (COD). The rate of reaction for removal of colloidal COD was slow and comparable to that for soluble organic matter.

The need to improve on-site wastewater treatment processes is being realized as populations move into more environmentally sensitive regions and regulators adopt the total maximum daily load approach to watershed management. Under many conditions, septic systems do not provide adequate treatment; therefore, advanced systems are required. These systems must remove significant amounts of biochemical oxygen demand (BOD) and suspended solids, and substantially nitrify, denitrify, and remove phosphorus. Many existing advanced on-site wastewater systems effectively remove BOD, suspended solids, and ammonia, but few substantially denitrify and uptake phosphorus. The purpose of this research was to design and test modifications to an existing on-site wastewater treatment system to improve denitrification and phosphorus removal. The Nayadic (Consolidated Treatment Systems, Inc., Franklin, Ohio), an established, commercially available, extended-aeration, activated sludge process, was used to represent a typical existing system. Several modifications were considered based on a literature review, and the option with the best potential was tested. To improve denitrification, a supplemental treatment tank was installed before the Nayadic and a combination flow splitter, sump, and pump box with a recirculation system was installed after it. A recirculation pump returned a high proportion of the system effluent back to the supplemental treatment tank. Two supplemental treatment tank sizes, three flowrates, and three recirculation rates were tested. Actual wastewater was dosed as brief slugs to the system in accordance with a set schedule. Several ion-exchange resins housed in a contact column were tested on the effluent for their potential to remove phosphorus. Low effluent levels of five-day biochemical oxygen demand, suspended solids, and total nitrogen were achieved and substantial phosphorous removal was also achieved using a 3780-L supplemental treatment tank, a recirculation ratio of 5:1, and a fine-grain activated aluminum-oxide-exchange media. Good results were also obtained with an 1890-L supplemental treatment tank and a recirculation ratio of 3:1. The most significant benefit of the supplemental treatment tank, in combination with the recirculation system, appears to be the low nitrogen concentration dosed to the Nayadic. By reducing the nitrogen concentration and spreading out its mass over time during no-flow periods, the Nayadic's inherent low-level denitrifying capacity was more closely matched and effective treatment was achieved.

Rapid expansion of wineries in rural California during the past three decades has created contamination problems related to winery wastewater treatment and disposal; however, little information is available about performance of on-site treatment systems. Here, the project objective was to determine full-scale, subsurface-flow constructed wetland retention times and treatment performance through assessment of water quality by daily sampling of total dissolved solids, pH, total suspended solids, chemical oxygen demand (COD), tannins, nitrate, ammonium, total Kjeldahl nitrogen, phosphate, sulfate, and sulfide across operating systems for winery wastewater treatment. Measurements were conducted during both the fall crush season of heavy loading and the spring following bottling and racking operations at the winery. Simple decay model coefficients for these constituents as well as COD and tannin removal efficiencies from winery wastewater in bench-scale reactors are also determined. The bench-scale study used upward-flow, inoculated attached-growth (pea-gravel substrate) reactors fed synthetic winery wastewater. Inlet and outlet tracer studies for determination of actual retention times were essential to analyses of treatment performance from an operational subsurface-flow constructed wetland that had been overloaded due to failure to install a pretreatment system for suspended solids removal. Less intensive sampling conducted at a smaller operational winery wastewater constructed wetland that had used pretreatment suspended solids removal and aeration indicated that the constructed wetlands were capable of complete organic load removal from the winery wastewater.

Using the solids flux theory, two quantities (i.e., the dimensionless limiting solids flux [G = kGL/v(o)] and the dimensionless underflow velocity [U = FR/(Av(o))] are introduced for a final clarifier based on the Vesilind equation of sludge zone-settling velocity (v = v(o) exp[-kX], where X is the suspended solids concentration, v(o) and k are empirical coefficients, and GL, FR, and A are the limiting solids flux, recycle flowrate, and surface area of the settling tank, respectively). In this paper, the dimensionless limiting solids flux is shown to be a function of the dimensionless underflow velocity only and is accurately represented by empirical equations. The limiting solids flux can, thus, be easily calculated by using the empirical equations without resorting to tedious numerical procedures. Furthermore, using the dimensionless quantities (G and U), two final clarifier equations that express the relationship among suspended solids concentration, surface area of the clarifier, recycle flowrate, and wastewater flowrate are derived. Their applications to final clarifier analysis and to determining required surface area of final clarifier are illustrated.

A pilot-scale, constructed wetland system consisting of a free water surface (FWS) and a subsurface flow (SF) wetland operated in series was set up for treating aquaculture farm wastewater. This study examined the system start-up phenomena and evaluated its performance in removing suspended solids, algae, and chemical oxygen demand (COD) under various hydraulic loading rates (1.8 to 13.5 cm/d). The SF wetland achieved stable effluent qualities without an adaptation period, while the FWS wetland required approximately 5 months to reach consistent removal levels for suspended solids and algae. Macrophyte density was a critical factor affecting the reduction of suspended solids and chlorophyll for the FWS wetland, but not for the SF wetland. Suspended solids removals in both of the wetlands and the combined system (47 to 86%) decreased significantly as the hydraulic loading rate increased, strongly following the first-order mass-decrease equation. Phytoplankton solids (biomass and detritus) were a primary source of suspended solids in the aquaculture wastewater. Both chlorophyll reduction (76 to 95%) and COD removal (25 to 55%) in the constructed wetland system were apparently not affected by hydraulic loading. While algae died out because of limited sunlight in both wetlands, algae detritus probably still contributed fine particles that were difficult to remove from the water by either filtering or settling out. Removed suspended solids did not result in the increase of COD and nutrients, indicating that further solids stabilization occurred in the wetland system.

A new criterion called the effluent upflow velocity (EUV) is proposed as an important parameter affecting secondary clarifier performance under hydraulically limited conditions. Defined as the upflow velocity in the effluent withdrawal zone of a secondary clarifier, the EUV is proposed as having a direct link to clarifier performance in the presence of a wide range of particle size distributions in the effluent withdrawal zone. It is hypothesized that a wide range of particle size distributions in the effluent withdrawal zone of a clarifier could result from one of two factors: poor mixed liquor flocculation characteristics or strong density currents capable of resuspending previously settled floc. Consequently, in the presence of either of these factors, the EUV would likely show the best correlation with clarifier effluent suspended solids, more so than traditional hydraulic criteria such as the surface overflow rate or weir loading rate. Results from clarifier modifications completed at the County Sanitation Districts of Orange County's Wastewater Treatment Plant No. 2 in Huntington Beach, California, are presented in support of this hypothesis.

Treatment of brewery wastewater was performed using an aerobic fixed-film sequencing batch reactor using a feedback control system based on dissolved oxygen concentration in the mixed liquor. This control system was modeled after the self-cycling fermentation technique. The system was operated at 25 and 35°C and under growth-rate limiting conditions. Total biochemical oxygen demand (TBOD) removal efficiency was 83% after 3 hours at 25°C and 92% after 1.5 to 2 hours at 35°C. The treated effluent produced had a TBOD between 120 and 438 mg/L, with suspended solids contributing between 63 and 71% of the TBOD. Effectiveness of the treatment process might be improved if an efficient secondary clarifier was installed or if the suspended solids were removed from the brewery wastewater before treatment.

Adaptation of the enhanced chemiluminescent reaction (ECLOX test) to water-quality monitoring revealed that pollutants in industrial and domestic effluent and farmyard and dairy washings may suppress or completely inhibit enhanced chemiluminescent light emission. Inhibition or changes in the kinetics of light emission occur in the presence of a wide range of extraneous substances. Interaction of such substances with ECLOX reaction components or reaction intermediates can produce changes in light emission, allowing detection of a broad range of chemical pollutants. This work examined the suitability of the ECLOX test to differentiate between water quality at various points along a rural stream. In addition, the study was used to measure whether changes in water quality detected by the ECLOX test were consistent with measured levels of the protozoan parasite Cryptosporidium parvum. Seven locations along a stream and a farmyard drainage ditch were sampled on the basis of position, continuity of flow, permanence, and evidence of fecal contamination. The stream frequently contained C. parvum (75% of occasions tested), although according to the ECLOX test and other standard parameters (suspended solids and pH), it seemed relatively uncontaminated. The ECLOX test did, however, distinguish among a range of water qualities. The ECLOX test can be considered as a useful qualitative indicator of differing water qualities, but C. parvum can be present in water of any quality; therefore, ECLOX is not an appropriate method for detecting the presence of this parasite.

This paper presents the results of a study to assess the effects of impervious and pervious (or porous) asphalt on the quality of runoff from highways in the Netherlands. Furthermore, the effects of settling and filtration on the quality of runoff of both types of asphalt have been elaborated. This study has been performed to support decisionmaking on how to deal with polluted runoff from highways in the Netherlands. The results show that runoff from well-maintained pervious asphalt contains a relatively low concentration of pollutants such as heavy metals, mineral oil, polynuclear aromatic hydrocarbons, and suspended solids compared to runoff from impervious asphalt. In runoff from both types of asphalt, copper, lead, and zinc are the prevailing heavy metals. The impression exists that especially the hard shoulders along highways provided with pervious asphalt act as a sink for suspended solids, soil particles, and other pollutants. To maintain its permeability and filter action, the hard shoulders should be regularly cleaned. Water treatment tests in the laboratory revealed that treatment of runoff from pervious asphalt results in lower efficiencies in the removal of heavy metals, compared with the treatment of runoff from impervious asphalt. This is probably because of the lower concentration of suspended solids and the difference in partitioning of the metals in the soluble and particle-bound phase. However, despite encouraging findings, long-term research on the continued permeability of pervious asphalt is lacking. As a result, its long-term performance with and without aggressive maintenance cannot be predicted at this time. The results of this study show that the current switch from impervious to pervious asphalt on Dutch highways has certain environmental benefits. The combination of low concentrations of pollutants, poor treatment efficiencies, and high costs makes it questionable whether additional treatment of runoff from pervious asphalt by means of settling basins or sand filtration is meaningful. Despite other positive properties of pervious asphalt such as noise abatement and less spray and skid resistance during wet weather, the rather moderate behavior of pervious asphalt with respect to slipperiness in winter should always remain an important point of attention when choosing this type of pavement.

To understand the effect of temperature induced density currents on circular clarifiers, a field study was performed on three uncovered circular tanks in Oregon during periods of low flow and high surface cooling. Temperatures were measured as a function of radial position and tank depth. Meteorological parameters were also measured in order to compute the surface heat flux from the water surface. The water temperatures in the tank were often 20 to 30 o C warmer than the equilibrium temperature. These studies showed that density currents and unstable temperature gradients were common. Surface temperatures were often about 1 o C cooler than bottom temperatures. The momentum and suspended solids of the inflow caused a density current that moved along the clarifier bottom and then rose near the middle of the tank. In the winter, this density current rose as a result of the decrease of initial momentum of the inflow, the buoyancy of the inflow after suspended solids had settled, and the geometry of the tank. Also, vertical velocities induced by surface cooling were two orders of magnitude greater than the overflow rate. This suggests that particles could be kept in suspension by convective currents.

This paper investigates a number of methods that can be used to generate constituent concentrations for use in stormwater modeling. These include the use of event mean concentrations (EMCs) and pollutant buildup and washoff formulations. Suspended solids data collected in the Austin, Texas, area from single-land-use watersheds were used to evaluate the usefulness of these methods. Use of a single EMC for all urban land uses was shown to provide a reasonable estimate of solids loads. This suggests that increases in total suspended solids loads resulting from development will be primarily a function of the increase in runoff volume, which in turn may be related to increased impervious cover. Water quality data did not indicate a strong correlation between initial pollutant load on the watershed and length of the antecedent dry period; however, the concentration of suspended solids in stormwater runoff does follow a simple washoff model.

A study at the Southeast Water Pollution Control Plant, San Francisco, California, was undertaken to evaluate the feasibility of replacing its current secondary effluent chlorination system with a 6.57 m 3 /s ultraviolet (UV) disinfection system. Two vertical lamp units and one horizontal lamp unit were pilot tested in parallel. The effective UV dose for coliform removal and the effects of feedwater characteristics and reactor hydraulics were examined. The horizontal pilot unit gave a more consistent performance than the vertical pilot units. Based on the test results, a UV dose of 65 mW s/cm 2 would be required for the plant to achieve the target effluent total coliform level (240 CFU/100 mL) 95% of the time. The large fluctuation of UV disinfection results could be attributed to the wide range of feedwater quality inherent to a combined sewer system. High suspended solids, characteristic of the plant's secondary effluent during storm events, significantly increased the UV dose required to achieve the target coliform level. Existing UV inactivation models were evaluated. The hydraulic behavior of the pilot units was found to significantly affect their test results. Higher virus removal efficiency was observed with the UV systems than the full-scale chlorination system.

The presence of dissolved organic matter (DOM) in a wastewater treatment system can significantly affect the uptake of heavy metals by sludge particulates. The characteristics of DOM, its concentration, and the solution pH are important parameters governing the heavy metals uptake reaction. The characteristics of DOM of various wastewater and sludge (primary, secondary, and tertiary) samples collected from four municipal wastewater treatment plants were investigated. Results showed that the dissolution of DOM from sludge is significantly affected by pH and suspended solids concentration. Results also showed that DOM contains two discrete acid groups that are available for metals complexation. The site concentration and acidity constants were determined by an alkalimetric titration method. For all DOM samples studied, the acidity constants, pK{sub aA} and pK{sub aB}, were 5.3 and 9.5, respectively. Based on the acidity constants and the Fourier transform infrared spectra, it is believed that the acid sites consist of carboxylic and amino functional groups. The density of the first acid site was approximately 10{sup {minus}5} mol/mg chemical oxygen demand for all samples studied. However, the density of the second acid site varied significantly among the DOM samples investigated.

It is anticipated that the West Windsor Pollution Control Plant (WWPCP) (Windsor, Ontario, Canada) will be required to be upgraded from its current chemical primary treatment to full secondary treatment, with phosphorus removal maintained. A steering committee established effluent design objectives for effluent suspended solids and total 5-day biochemical oxygen demand of 15 mg/L, total phosphorus of 0.5 mg/L, and ammonia-nitrogen of 3 mg/L. Four processes were tested; among these, the trickling filter/solids contact (TF/SC) process had not been tested previously for consistent nitrification in colder climates where average monthly wastewater temperatures fall to 9 to 10°C. A novel TF/SC treatment scheme was identified that took advantage of the low biochemical oxygen demand of the WWPCP's chemical primary effluent and used higher density cross-flow media than had previously been used in the TF/SC process to achieve nitrification. In initial testing, the TF/SC process nitrified successfully but failed to meet the other objectives. A detailed diagnosis showed that the best process configuration had not been tested and that the pilot design was flawed in several respects. The inclusion of a sludge reaeration tank, the substitution of a flocculator-clarifier for a conventional scraper clarifier, and the elimination of head losses causing excessive floc breakup corrected the problem. In testing over a year-long period, the TF/SC process consistently met the target objectives, moving it up from fourth place to a tie with the other first-ranked process, the biological aerated filter (BAF). Capital costs were found to be lower than for the activated-sludge process and the BAF processes.

Operating diagrams for secondary clarification of activated sludge were developed based on the solids flux theory. The diagrams connect the process operational parameters-mixed liquor suspended solids, return activated sludge solids, and recycle ratio-in a unified graphical form. The diagrams can be used to design and analyze the performance of secondary clarification and to evaluate operating strategies in response to changes in flow rate or solids settleability.

This study develops a remote sensing technique for real-time monitoring of wastewater effluents stored before irrigation. Reflectance and attenuation coefficients for downwelling irradiance spectra (400 to 950 nm spectral resolution of 2 nm) were acquired simultaneously with turbidity, chlorophyll, organic matter, and total suspended matter concentrations in the Naan wastewater system, Israel. High-spectral-resolution spectrometric data were used to select the most suitable spectral bands for remote sensing of optically active constituent concentrations. Algorithms for remote estimation of wastewater quality expressed as chlorophyll-α, bacteriochlorophyll-α, and total suspended matter concentrations were developed. Reflectance height at 720 nm and an area above the base line from 670 to 950 nm was used in algorithms for chlorophyll-α assessment (r 2 > 0.83). For bacteriochlorophyll-α assessment, an area under the base line through 780 to 900 nm was used, allowing its quantitative estimation (r 2 > 0.94). Reflectance of approximately 570 and from 400 to 950 nm correlated closely with total suspended matter concentration (r 2 > 0.82) and was used to retrieve it from reflectance spectra. This is the first reported study on the quantitative remote assessment of wastewater quality. The results suggest that four spectral bands be used for real-time monitoring of wastewater ponds quality.

A 5670-m 2 wet detention pond draining a predominantly residential urban area was monitored for flow, suspended solids, bedload, particle-size distribution, and selected pollutants during 16 storm events. Both suspended solids concentrations and particle-size distribution of the suspended solids in runoff water exhibited large variations between storms. Though a portion of particles larger than the pond's critical particle size left the pond, the pond removed 87% of the total suspended solids entering the pond. The relative proportion of clay-size particles increased from 36 to 72%. Sand- and silt-size fractions both decreased. Heavier particulate material saltating along the channel bottom, termed bedload, composed an average of 14% of the total particulate mass or load to the pond. The pond's sediment and associated pollutant removal efficiencies were influenced by influent particle-size distribution.

Repair of wastewater microorganisms after ultraviolet (UV) disinfection was studied by incubating secondary effluent previously irradiated to UV doses of 40 to 60 mW.s/cm 2 in diffusion chambers for 2 to 24 hours. For somatic coliphage repair estimations, the effluent was incubated in flasks for 2 hours. There was only slight repair of fecal streptococci, and it did not depend on the UV irradiation dose. Repair of the thermotolerant coliforms was a function of the UV dose. Repair corresponded to a maximum increase of 1 log unit after irradiation to 40 mW.s/cm 2 , and to smaller increases after 50 or 60 mW. s/cm 2 . No relationship was observed between repair and suspended solids content of the effluent in the range of 4 to 12 mg/L. For the Salmonella, no repair was observed after a 60-mW.s/cm 2 irradiation and a 24-hour incubation. No repair was observed for the viruses in nine in-flask incubations, with coliforms showing increases between 1 and 2 log units in the same flasks. Compared with the coliforms, this absence of repair of microorganisms that cause the greatest health risk in bathing and shellfish-breeding zones brings interesting perspectives in the debate of post-UV-irradiation repair.

The effect of the enhanced biological phosphorus removal process (EBPR) on waste activated sludge (WAS) production and the type of phosphorus storage were investigated in two continuous-flow activated-sludge systems in a semitechnical scale. One of the plants was operated with the A/O® process, whereas the other plant was operated in a conventional, fully aerobic mode and served as a control. By monitoring the elementary composition of the activated-sludge solids in plant II and by using phosphorus fractionations, it was found that nearly all of the enhanced phosphorus removal was due to storage as polyphosphate (poly-P). The additional uptake of phosphorus resulted in an increase of the inorganic sludge mass, which was determined to be 3.05 g suspended solids (SS)/g P using the results of the measurements of the nonvolatile solid fraction. This value was confirmed experimentally by the measurement of the difference between the WAS production of plant I and plant II. Based on the specific WAS production, an additional dry solids production of 3.14 g SS/g P was calculated. No indications for a significant difference of the organic sludge production between both plants were found, although the organic WAS production was slightly higher in experimental periods with a relatively high phosphorus content of the activated-sludge solids of plant II.

An empirical ultraviolet (UV) disinfection model was developed to predict coliform inactivation in unfiltered secondary wastewater effluent. The model was developed in the tailing region of the UV dose-response curve for log survival values less than -3. Input parameters to the model include the suspended solids concentration, the unfiltered UV transmittance measured at a wavelength of 253.7 nm, the influent coliform concentration before exposure to UV light, and the applied UV dose. In the model, UV dose is calculated as the average UV intensity within the reactor (using the point source summation method) multiplied by the exposure time (based on the assumption of approximate plug flow conditions). Because the model is empirical, it should be calibrated to establish the statistical significance of each input parameter before use in a particular situation and to implicitly account for other factors influencing disinfection performance. The model was calibrated with data collected from a small-scale UV reactor operated at two northem California wastewater treatment plants. The values of suspended solids concentration, unfiltered UV transmittance, and UV dose were found to be statistically significant with the water quality data set considered. The correlation coefficient (R 2 ) of the calibrated model was 0.79. The calibrated model was then used to illustrate a design approach that integrates model uncertainty, wastewater variability, and variable permit requirements. In this approach, the number of UV lamps, modules, banks, and channels can be optimized to provide cost-effective designs. Several design examples are used to illustrate both disinfection and headloss considerations in the recommended design approach. Water Environ. Res., 68, 900 (1996).