Showing papers on "Suspended solids published in 2001"

Modeling underwater light climate in relation to sedimentation, resuspension, water quality and autotrophic growth

Abstract: The underwater light climate ultimately determines the depth distribution, abundance and primary production of autotrophs suspended within and rooted beneath the water column This paper addresses the underwater light climate, with reference to effects of suspended solids and growth responses of autotrophs with emphasis on phytoplankton Effects of the most important factors contributing to the absorption and scattering of light in surface waters were described A comparison between spectral and scalar approaches to underwater light climate modeling was made and examples of linear approximations to light attenuation equations were presented It was demonstrated that spectral and scalar photosynthesis models may converge to similar values in spectral-flat, high photon flux environments, but that scalar PAR models may overestimate biomass-specific production by 70% Such differences can lead to serious overestimates of habitat suitability for the growth and survival of submersed macrophytes, particularly in relatively turbid, coastal waters Relationships between physical and optical properties of suspended sediments were described theoretically, and illustrated with modeling examples and measurements It was found that the slowly settling particulate fraction contributed substantially to the suspended solids concentration, and greatly to light attenuation within the water column It was concluded that distinguishing particles by fall velocity and concomitant light attenuation properties in the modeling of underwater light conditions allowed the establishment of useful, although not simply linear, relationships In eutrophic, shallow lakes, the largest contribution to light attenuation often originates from phytoplankton on a seasonal basis (months–years), but from suspended solids behavior on a shorter time scale (days–weeks), particularly when water bodies are wind-exposed Temporal and spatial variabilities in wave height, suspended solids concentrations, and light attenuation within the water column, and their importance for autotrophic growth were described, and illustrated with a case study pertaining to Markermeer, The Netherlands The influence of underwater light conditions on phytoplankton succession was briefly discussed and illustrated with a case study pertaining to Lake Veluwe, The Netherlands It was concluded that modeling the underwater light climate in a water body on a few sites only can indicate how important various components are for the attenuation of light, but based on the current state of the art, it can not be expected that this will provide accurate predictions of the underwater light climate, and of phytoplankton and submersed macrophyte growth

Assessment of the risk of phosphorus loading due to resuspended sediment.

Abstract: Resuspension is a multiphase phenomenon where suspended solids encounter water layers differing in physico-chemical properties that affect the reactions of phosphorus (P). The role of resuspended sediment as a sink or source of dissolved P was determined in a laboratory study of P desorption-sorption equilibria. Gradual mixing was simulated using decreasing solid concentrations and varying environmental conditions (pH, redox, ionic strength). To describe the P exchange when the particles encounter dissimilar water layers, the extent of P sorption to or desorption from solids was expressed as a function of P concentration in the bath solutions. The equilibrium phosphorus concentration (EPC), at which there is no net P release from or retention to the particles, proved to be a suitable parameter for assessment of P load risk. Under oxic conditions at pH 7, commonly prevailing in lakes, the EPC values ranged from 11 to 27 microg P L(-1). The larger the water volume the suspended material was mixed with, the higher the P concentration, allowing desorption to occur. As for chemical factors affecting P mobilization, EPC followed the order: pH 7 < pH 7 anoxic < pH 9. A separate extraction experiment revealed that elevated pH enhanced P mobilization more as the concentration of solids decresed. The results demonstrate that high pH (a common characteristic in eutrophic lakes during summer), when linked with intensive resuspension, may markedly increase the internal P loading risk. As for the risk assessment, the quantification of the internal P loading would be improved by isotherm studies combined with field observations.

Effects of turbidity and suspended solids on salmonids

Abstract: Protection of Washington State's salmonids requires that transportation officials consider the effect of suspended sediments released into streams during transportation projects. Many state and provincial criteria are based on a threshold of exceedance for background levels of turbidity. However, determining natural background levels of turbidity is a difficult endeavor. The inconsistent correlation between turbidity measurements and mass of suspended solids, as well as the difficulty in achieving repeatability using turbidimeters contributes to concerns that turbidity may not be a consistent and reliable tool determining the effects of suspended solids on salmonids. Other factors, such as life stage, time of year, size and angularity of sediment, availability of off-channel and tributary habitat, and composition of sediment may be more telling in determining the effect of sediment on salmonids in Northwestern rivers. For short-term construction projects, operators will need to measure background turbidities on a case by case basis to determine if they are exceeding regulations. However, transportation projects may also produce long-term, chronic effects. To adequately protect salmonids during their freshwater residence, Total Suspended Solids (TSS) data on physiological, behavioral, and habitat effects should be viewed in a layer context, incorporating both the spatial geometry of suitable habitat and the temporal changes associated with life history, year class, and climate variability. Spatial and temporal considerations provide the foundation to decipher legacy effects as well as cumulative and synergistic effects on salmonid protection and recovery.

Suspended particles in the drinking water of two distribution systems

Abstract: The concentrations of suspended particles were measured in the drinking water of two distribution systems, and the nature of these particles documented. The concentrations of particulate matter were invariably found to be small (maximum 350 μg/L). They are globally in the very low range in comparison with dissolved matter concentrations, which are measured in several hundreds of mg/L. Except during special water quality events, such as turnover of the raw water resource, results show that organic matter represents the most important fraction of suspended solids (from 40 to 76%) in treated and distributed water. Examination of the nature of the particles made it possible to develop several hypotheses about the type of particles penetrating Montreal's distribution system during the turnover period (algae skeleton, clays). These particles were found to have been transported throughout the distribution systems quite easily, and this could result in the accumulation of deposits if their surface charge were ever even slightly destabilised, or if the particles were to penetrate the laminar flow areas that are fairly typical of remote locations in distribution systems.

Particle effects on ultraviolet disinfection of coliform bacteria in recycled water.

Abstract: Pilot- and bench-scale coliform inactivation tests with UV irradiation were used to show how suspended solids remaining in filtered secondary effluent affect the efficiency of the UV disinfection process. Observed kinetic inactivation rates decreased with increasing suspended particle sizes of 7 microm or larger present in tertiary effluent. First-order inactivation rates estimated from collimated beam dose-response curves for discrete ranges of UV doses were substantially different, which should caution researchers not to compare inactivation data obtained with largely dissimilar UV doses or suspended particle distributions. A dose of approximately 800 J/m2 was identified as the minimum dose that will consistently meet the California wastewater reclamation coliform criterion when applied to in-line filtration effluent.

The use of mangrove wetland as a biofilter to treat shrimp pond effluents: preliminary results of an experiment on the Caribbean coast of Colombia

Abstract: The potential benefit of integrating mangrove and shrimp farms to protect ponds against erosion, to enhance the productivity of supply water and also to treat pond effluents has been pointed out previously. Agrosoledad, a 286-ha shrimp farm located on the Caribbean coast of Colombia, was constructed behind a 1-km-wide mangrove area. Farm effluents are partially recirculated through a 120-ha mangrove wetland used as a biofilter. A 3-month study compared the concentrations of suspended solids and inorganic nutrients in the supply canal, the pond drainage and the biofilter. Suspended solids increased in pond drainage compared with supply water, but they were drastically reduced in the biofilter. In contrast, dissolved inorganic nitrogen and phosphorus concentrations were not different in supply water and pond drainage, but they increased in the biofilter because of the presence of a large marine bird community. Additionally, a significant decrease in dissolved oxygen and pH was observed in the biofilter. The study demonstrated the efficiency of the system to eliminate suspended solids from the effluent. However, nutrient dynamics showed that the possible use of mangrove wetlands as biofilters for effluent treatment will be less predictable than expected.

Process and apparatus for the treatment of waste water

Abstract: A process and apparatus for treating waste water using a sequencing batch reactor system in conjunction with a membrane filtration device for solids/liquid separation provides a highly efficient method and apparatus for the removal of organic contaminants, nutrients and suspended solids from waste water. A three-phase cycle is used, consisting of a mix fill phase, a react fill phase and a react discharge phase. In the mix fill phase the reactor environment is controlled to provide an initial anaerobic time period for achieving phosphorous release and denitrification of oxidized nitrogen present in the reactor from the prior cycle. In the react fill phase waste water continues to enter the reactor. The reactor environment is controlled to provide alternating periods of aeration and mixing and mixing only to promote completely mixed aerobic and anoxic conditions. The alternating periods of aerobic and anoxic conditions promote the oxidation of organic and nitrogenous waste products and the biological uptake of phosphorous followed by the denitrification of oxidized nitrogen. Finally, in the react discharge phase, waste water flow into the reactor ceases. The reactor environment is still controlled to provide alternating periods of aerobic and anoxic conditions. The waste water in the reactor is directed to a membrane device for solids/liquid separation. The solids/liquid mixture that does not pass through the membrane is returned to the reactor. This treatment approach eliminates the necessity to provide separate anaerobic and anoxic basins. The combination of the membrane device with the sequencing batch reactor process eliminates the necessity to provide appropriate time periods for a quiescent environment for solids/liquid separation and the requirement of mechanical decanter devices normally required to extract the desired effluent quality in conventional sequencing batch reactor systems.

Limits of Physicochemical Treatment of Wastewater in the Vegetable Oil Refining Industry

Abstract: This paper presents results of investigations on physicochemical treatment of vegetable oil refinery wastewater (VORW), namely acid and technological wastewater. The study has shown that VORW has a varying high pollution load (organic matter, sulfates, phosphates and chlorides) and the removal of these pollutants from acid wastewater was more effective than that from technological wastewater; the removal of suspended solids and solvent extractables was relatively higher than that of BOD5 and COD. The use of calcium chloride and alum as coagulants increases the concentration of chlorides in the final treated wastewater. The results also showed that physicochemical treatment processes significantly influence the relative biodegradability of the organic matter in the wastewater.

Nature and Dynamics of Water Sediment Interface in Combined Sewers

Abstract: The measurement of suspended solid concentration profiles in dry weather wastewater of the “Le Marais” combined sewer network, Paris, has shown an increase in concentration in the lower part of the sewer’s flow (1–3 g/\il). To obtain a precise description of the composition of the water-sediment interface, an observation system was set up, which showed that an immobile layer composed of fibers and organic matter formed at the bottom of trunks over the coarse mineral deposits. The concentration profiles obtained result from the removal of this layer by aspiration. Samples were taken from this organic layer using a specially adapted system. The accumulation rate of the organic layer is 215 g/(m\U2.\Nday). The particles of this organic layer are heavily loaded with pollutants (volatile solids to suspended solids = 66–75%). This layer is located at points where the shear stress is <0.1 N/m². Flush experiments have shown that it can be eroded by small rainfall events. When these results are extrapolated over the whole catchment area by mapping the organic layer, they show that the organic layer is stored in the same quantities as the mass eroded during a rainfall event in the sewer system and it can therefore contribute to pollution in urban storm-water discharge.

Apparatus and method for thermal desalination based on pressurized formation and evaporation of droplets

Abstract: A method for removing dissolved solids, particularly salts, from water. An apparatus for performing the inventive method is disclosed. The aqueous solution to be treated, for example sea water, is atomized using special non-pneumatic nozzles, and sprayed into an evaporation chamber through which air, heated by waste heat, is blown. The micro-droplets undergo rapid evaporation in the chamber, resulting in the separation of the salt solids from the vapor phase of the water. The mixture of suspended solids and water vapor is filtered to remove and collect the salts, and the water vapor is condensed to collect the salt-free water.

Reclaiming water and usable brine concentrate from domestic sewage

Abstract: A method of processing sewage. Non-biodegradable solids are first removed from the sewage for separate disposal. The sewage is then introduced to the bottom of a fermentation cell designed to optimize sedimentation and methane fermentation of settleable organic solids, most of which settle in the fermentation cell. Sulfate-reducing micro-organisms that release sulfides are growing in the fermentation cell. The sulfides released combine with multivalent metal particles in the sewage to form insoluble particles, a portion of which settles in the fermentation cell. The remaining metal sulfides, other suspended solids, microorganisms, nutrients, and pathogens in the sewage are then removed by natural means followed by Dissolved Air Flotation, Slow Sand Filtration and disinfection. Metal ions that escaped sedimentation in the fermentation cell are adsorbed by microorganisms that have a strong negative surface charge. Finally, reverse osmosis is carried out to produce purified water and a high-salinity concentrate. The purified water and the high-salinity concentrate, being substantially free of toxic multivalent metal particles, can be used respectively for safe human consumption and for cultivation of halophilic microalgae.

Method and apparatus for recovery of waste water

Abstract: An apparatus and method for recovering wastewater from laundry operations. A substantially closed loop series of tanks, conduits and pumps hold and transfer water output from a wash machine through a series of filters, including a lint pulloff filter, a multimedia pressure filter, a clay filter, and a carbon filter. The water is ozonated to coagulate suspended solids and to disinfect and is subjected to ultraviolet light to disinfect and to reduce residual ozone.