Lime Precipitation Research Articles

Polluting characteristics and lime precipitation of olive mill wastewater

Abstract Olive mill wastewaters originating from olive extraction units are the most polluted wastewaters of the food industry which present a toxicity towards plants as well as certain impacts to the hydro‐flora. Pollution abatement for olive mill wastewater is difficult, because they are seasonal, highly concentrated, very polluting, and the processing units are small, and can not withstand the cost of a depollution. This paper mainly concentrates on the polluting characteristics and lime precipitation as a minimal pre‐treatment procedure for the removal of organic matter content. The sludge produced of the addition of 0.5–3% CaO reduces the concentration of suspended solids in the “vegetation waters”; by 27.6% whereas 77.1% of the oil and grease are distributed in the precipitate fraction. The COD as well as the toxic load in terms of phenolic compounds are not strongly affected by the addition of CaO.

Purification of nickel sulphate solutions containing iron, copper, cobalt, zinc and manganese

AbstractAcidic nickel‐bearing solution containing iron, cobalt, manganese, zinc and copper was processed through a solvent extraction and precipitation technique to obtain a pure nickel sulphate solution. Iron was extracted using 0.2M Cyanex‐272 (partially neutralised) as the extractant. Stripping of iron from the loaded organic has also been studied. After iron recovery through solvent extraction the raffinate still contained 0·25 g dm−3 of iron which was quantitatively separated by a lime precipitation technique. During this iron precipitation there was no loss of cobalt and nickel but copper, manganese and zinc were coprecipitated to some extent. From the iron‐free nickel sulphate solution the other impurities were extracted using the same extractant (Cyanex‐272) in a single stage. The metal ions from the loaded organic were stripped using a 0·5% (v/v) H2SO4 solution in a single stage. The entire operation needs only seven stages: two stages for iron extraction, three stages for iron stripping from the loaded organic, and one stage each for extraction and stripping of other impurities. In the entire operation the loss of nickel was less than 0·5%.

Use of Monte Carlo techniques to assess POTW compliance with EPA water quality criteria for heavy metals

ABSTRACT: This paper presents the results of a study (Larry Walker Associates, 1990) to determine the nature of additional controls necessary for the Sacramento Regional Wastewater Treatment Plant (Regional Plant) to comply with the numeric water quality objectives for metals recently adopted by the State of California. In addition, the impact of Regional Plant effluent on Sacramento River metals concentrations is examined, and the costs of compliance with the new objectives are estimated. Monte Carlo techniques are used to determine the ability of the Regional Plant to achieve the metals objectives and the effects of treatment plant discharge on receiving water metal concentrations. Frequency distributions of advanced treatment efficiencies, such as lime precipitation and reverse osmosis, are used to simulate effluent concentration reductions that are potentially achievable. The costs associated with the additional treatment required to meet objectives are estimated using published cost estimates for advanced treatment plants of similar size. Results show that currently, the Regional Plant does not meet objectives for cadmium, copper, mercury, and zinc. Furthermore, the additional treatments evaluated would not completely eliminate violations of the copper and mercury objectives.

Grazing as a cause of lime precipitation in a natraqualf

Abstract The movement of water from the watertable to the atmosphere is one of the most common causes for CaCO3 accumulation on top of the soil. In the Flooding Pampa, the increase in water evaporation due mainly to the reduction of soil cover as a result of grazing has given place to pulses of topsoil salinization. We investigated the influence of this process on lime precipitation in the upper horizon. Data from continuous grazed and ungrazed areas were considered. The relative ion concentrations in the upper horizon of the ungrazed area and in the phreatic water were very similar. Under grazing, absolute ion concentration was larger than in the water table. The anionic constituents did not increase directly and linearly. Chlorides and sulfates showed increments. The carbonate proportion did not change, but bicarbonates showed a relative decrease. This latter reduction could be related to the precipitation of CaCOs in the uppper horizon of the soil. In agreement, the Ion Activity Product (IAP) of the ca...

Precipitation and Coagulation of Organic Substances in Bleachery Effluents of Pulp Mills

The formation of chlorinated organic substances in bleachery effluents of pulp mills is avoided by changing the bleaching processes to nonchlorinating agents. However, high concentrations of poorly biodegradable and colored lignins are remaining. Precipitation can be one option in physico-chemical treatment of these waters. The influence of alum, lime and magnesium hydroxide as precipitation agents for two different bleachery wastewaters was investigated under various conditions. Alum prove to be the most effective precipitant. Application at an Al/DOC-ratio of 0.5 (g/g) yields a reduction of about 60 % of the soluble organic matter in chlorine-bleachery effluents at the pH = 5.5. Oxygen-bleachery effluents require only half of this specific dosage. Lime precipitation also causes low residual concentrations, but the high chemical demand leads to problems in application. The precipitation with magnesium hydroxide cannot be applied, because remaining concentrations of organic materials are quite high. The changes in bleaching processes are responsible for a new kind of wastewater, which has a significantly lower demand of precipitant

Treatment Technology Evaluation for Aqueous Metal and Cyanide Bearing Hazardous Wastes (F007)

As a result of recent developments In the area of hazardous waste management, the U.S. Environmental Protection Agency Is evaluating the performance of various technologies for the treatment and/or the destruction of certain wastes that are presently being disposed of In landfills and surface Impoundments. As a part of this program, the University of Cincinnati Is testing currently available treatment technologies that are applicable to metal- and cyanidebearing hazardous wastes at the U.S. EPA Test and Evaluation Facility In Cincinnati, Ohio. The following unit processes have been evaluated: alkaline chlorlnatlon, lime precipitation/ flocculation/settllng, multi-media filtration, anlon exchange, and cation exchange. Examination of several process configurations, utilizing the above-mentioned unit processes, did not produce any treatment train that could prevent codepositlon of cyanides and metals In the sludges when the feed stream contained mixed metals and complexed cyanides. It was also determined tha...

Liquid polymers keep drip irrigation lines from clogging

Clogging from lime (CaCO3) precipitation can be prevented by injecting a homopolymer of maleic anhydride into buried drip systems. Investigators prevented drip tubing from clogging in coastal strawberry plots by using this polymer and chlorine for high-bicarbonate waters.

Acid/Sugar Separation Using Ion Exclusion Resins: A Process Analysis and Design

Abstract The economic feasibility of using acid hydrolysis to convert agricultural waste products, such as corn stovers, to alcohol is very dependent upon developing a cost effective sulfuric acidglucose sugar separation process. Presently, an acid/sugar stream from sulfuric acid hydrolysis of cellulose is treated with lime to precipitate the acid as gypsum. This technique not only consumes acid and lime, but also generates waste gypsum that is sent to a landfill. An ion exclusion process to perform acid/sugar separation has been designed using standard resins. Economic analysis based on a process computer model indicates that ion exclusion is 40 % less costly than a lime precipitation process.

Effects of water-cement ratio, quantity and fineness of sand on the evolution of lime in set portland cement systems

The water-cement ratio and the quantity and fineness of sand are shown to influence the evolution of lime in set portland cement systems. Increasing the water-cement ratio from 0.30 to 0.50 caused an increase in Ca(OH) 2 content in both portland cement pastes and mortars at all ages of hydration. For the same water-cement ratios, however, the calcium hydroxide content of the mortars were found to be significantly higher than those of the pastes. With finer sand fractions and higher sand dosages, the rate of precipitation of lime in the mortars also increased. The results have been interpreted on the basis of a ‘through-solution’ mechanism of formation of CH in which after the hydrolysis of the calcium silicates C 3S and C 2S, calcium hydroxide precipitates out of solution as crystals. With respect to the mortars the sand particles are believed to act as a ‘sink’ for the CH crystals which precipitate out of the pore solution. With increasing water content the Ca 2+ and OH − ions become easily transported through the aqueous phase to the inert sand surfaces where favourable thermodynamic conditions exists for crystallization and growth of the Ca(OH) 2 crystals.

Processing of nickel- and cobalt-containing leach liquors obtained from different raw materials

Acidic as well as ammoniacal leach liquors obtained from three different raw materials, namely, lateritic nickel ores, copper converter slag and Indian Ocean manganese nodules, were treated for removal of impurities and separation of copper, nickel and cobalt. Precipitation and solvent extraction techniques were used for these purposes. Iron and silica impurities from acidic solutions were removed by lime precipitation. In ammoniacal medium, iron was coprecipitated with manganese. Manganese was removed as manganese dioxide by oxidative precipitation from both media; this removal also results in some loss of cobalt due to its adsorption on the manganese dioxide matrix. From sulphate solutions, copper was extracted using LIX 64N ® ∗ ∗ LIX is a registered trade mark of Henkel Corporation. followed by nickel-cobalt coextraction using di-2-ethylhexylphosphoric acid (D2EHPA). From the loaded solvent, nickel and cobalt were separated by the crowding technique. From ammoniacal solution, both copper and nickel were coextracted with LIX 64N and separated by selective stripping from the loaded organic phase. Cobalt was recovered either by sulphide precipitation or by adsorption on lignite followed by desorption with sulphuric acid/spent electrolyte.

Methods for removal of copper and iron from boiler chemical cleaning wastes

AbstractThis paper presents the results of field and laboratory studies conducted to evaluate treatment methods for reducing the concentrations of dissolved copper and iron in several spent boiler cleaning solutions. These waste solutions are generated during the cleaning of steam tubes in utility boilers. Cleaning may be accomplished using one of several solutions, including: inhibited hydrochloric acid, ammonium bromate, ethylenediamine tetraacetic acid (EDTA), citrate, and hydroxyacetic‐formic acid. The raw wastes were treated by conventional lime and caustic precipitation and by co‐ponding with coal fly ash. Analytical results were compared with Federal effluent discharge guidelines (NPDES) for copper and iron.

Physico‐chemical treatment of domestic wastewater

Abstract Three physico‐chemical treatment schemes investigated in this study include: (i) lime precipitation, and ozonation‐(ii) lime precipitation followed by ferrate treatment, filtration, and ozonation, and (iii) ferrate treatment followed by filtration, and ozonation. It was found that lime treatment followed by ozonation produced comparable effluent to the secondary treatment while other two schemes provided similar or better degree of treatment, however, the operation and maintenance of these two systems were more complex.

Biological Phosphorus Removal in Connection with Oxygen Aerated Activated Sludge Plants

Since the beginning of 1984 the phostrip process has been investigated in combination with an oxygen aerated activated sludge plant. This combination of phostrip and oxygen aeration can be expected to yield the following advantages:-Savings in stripper volume and lime dosage. If detention time of return sludge in the stripper is kept constant, the amount of phosphorus released is directly proportional to the dry weight of organic matter being treated. Since oxygen aeration renders an activated sludge with excellent settleability, the return sludge has a high concentration of suspended solids and thus a given amount of phosphorus can be eliminated in a smaller stripper volume. Furthermore, the concentration of phosporus in the stripper supernatant will be higher. As lime precipitation is not stoichiometric on calcium hydroxide but pH-dependent, the smaller amount and more highly concentrated stripper supernatant requires less calcium hydroxide for phosphorus precipitation.-High levels of dissolved oxygen in the aeration basin, as maintained with oxygen aeration, prevent undesired phosphorus release in the final clarifier.-The potential problem of pH-decline in an oxygen aerated basin due to carbon dioxide accumulation especially hazardous to nitrification can be overcome by side stream precipitation with lime. After precipitation, the side stream has an elevated pH and a high buffer capacity and will therefore antagonize the pH decline after being recharged into the aeration basin. Test trials in semi-technical scale were performed using a stripper of only 30% of the volume of the oxygen aerated basin. The stripper was a 2,6 m high column equipped with a rotating elutriant distribution system near the bottom of the column. Elutriation was employed to maintain an upward current of the liquid phase throughout the stripper in order to transfer most of the released phosphorus into the stripper supernatant. The stripper therefore does not accomplish any sludge thickening. Design and operation criteria of the stripper are comprehensively listed in Table 1. Results of two first test series are listed in Table 2. In both series the stripper was equally operated. The F/M ratio of the aeration basin was lowered in phase 2. It is obvious, that with respect to the total P input with primary treated sewage the P-elimination was not sufficient. In phase 1 only 57% of influent phosphorus was eliminated (34% by the stripper supernatant, 23% in the surplus sludge). It was anticipated that a higher P-elimination could be obtained in phase 2 by lowering the flow rate of the influent to the aeration basin and maintaining the same conditions in the stripper as in phase 1. Surprisingly the stripper efficiency was considerably lower. Consequently phosphorus uptake and release are determined by the F/M ratio in the aeration basin. other potential reasons for decreasing stripper efficiency could be excluded:-Nitrification had barely started and nitrate was not detectable in the return activated sludge.-Elutriation conditions were the same in both phases and elutriation efficiency of the stripper was about 40%.-P-release in the final clarifier was not observed, for concentrations of phosphate found in the effluent of the aeration basin were equal to those found in the secondary effluent. The low wastewater temperature could be a possible reason for insufficient P removal and might also be responsible for insufficient nitrification. It can be anticipated that for satisfactory phosphorus removal the stripper should have at least twice the volume of the stripper investigated, which is then 60% of aeration basin volume. The subject of further research is the optimization of the stripper operation in order to minimize necessary stripper volume.

Chemical‐Physical Leachate Treatment

The results of full-scale chemical physical treatment of sanitary landfill leachate are analyzed. The plant receives approximately 75,000 u cell (liters) per day from a lined 50 acre landfill. The treatment sequence consists of equalization, lime precipitation, sedimentation, and air stripping of ammonia. Overall percent removal efficiencies are BOD\d5, 69; kjeldahl-N, 53: cadmium, 59; copper, 38; iron, 98; lead, 66; mercury, 52; nickel, 54; zinc, 95, and, suspended solids, 95. Equalization markedly reduces operating costs. The effects of temperature and pH on heavy metals removal are also reviewed.

Copper Removal by an Adsorbing Colloid Foam Flotation Pilot Plant

Abstract There are many small metal-plating firms, and the Environmental Protection Agency estimates that the metal-plating industry will be the industry hardest hit by the new pretreatment standards which require dischargers to limit heavy metal discharges to very low concentrations (I). Existing methods of heavy metal removal, such as lime precipitation, are costly, require large tanks, produce a wet, bulky sludge, and usually require final filters for polishing if very low residual levels of metals are desired. Heavy metal removal methods which are cheaper, require less space (important in old businesses with limited land), and produce less sludge are needed.

Description of soil chemistry during transient solute transport

Leaching studies were conducted in six instrumented field plots to establish the validity of a soil chemistry‐solute transport model. The model was designed to predict the transport and solution concentrations of Ca2+, Mg2+, Na+, K+, HCO3−, CO32−, SO42−, and Cl− in a soil containing CaCO3 (lime) and CaSO4·2H2O (gypsum). The model includes description of the precipitation and dissolution of both lime and gypsum and considers cation exchange. Evaluations were made of the sensitivity and accuracy of model simulations under transient and steady state flow regimes and in cropped and noncropped situations. The leaching plots were instrumented with porous ceramic suction samplers, tensiometers, and neutron probe access tubes. Five different quality waters and three types of water management were used. The soil solution was sampled following each irrigation and analyzed for the cations and anions of interest. Comparisons of measured and predicted data showed the model to be reliable as a simulation tool to predict electrical conductivity under cropped conditions but unreliable in uncropped situations.

A Combined Salt Transport‐Chemical Equilibrium Model for Calcareous and Gypsiferous Soils

AbstractChemical precipitation‐dissolution and cation exchange subroutines were interfaced with an existing water movement‐salt transport model. Three model options available for testing the prediction of salt transport and storage were (i) individual ion transport without soil interaction, (ii) precipitation and dissolution of lime and gypsum during transport, and (iii) cation exchange in addition to the precipitation‐dissolution reactions. The transport model also predicts relative crop growth and water uptake as affected by soil moisture and salinity. The chemical subroutine used by the second and third options calculated ionic activities, corrected for ionic strength and ion pair formation, and was used to calculate lime and gypsum precipitation and dissolution. Cation activities were also used to calculate Ca, Mg, Na, and K exchange equilibria by a method that allows for addition of any number of exchangeable cations. Values predicted by the three options for EC, SAR and Ca, Mg, Na, K, Cl, SO4, and HCO3 concentrations were compared to experimental data obtained from a lysimeter study and were only satisfactorily predicted when both chemical precipitations and cation exchange were considered for a gypsiferous and a nongypsiferous soil irrigated with a high, medium, and low CaSO4 water at two leaching fractions.

The importance of glycerol in the fatty acid industry

AbstractHistorically, glycerol, a valuable by product of the fatty acid insutry, is priced higher in the market‐place than any of the common fatty acids. Glycerol “credit” from fat‐splitting, frequently in time of economic stress, makes the difference between a profitable stearic acid operation and an economically unsound one. Theoretical yields of glycerol for the common fats and oils range from 9–13.5%; practical plant yields, corrected for FFA and upgrading yield losses, are 9–12.8% on 100% glycerol basis, or 10.3–14.8% on an 88% glycerol basis. Glycerol “credit” per pound of fatty acid ranges from 1 to 3 cents/pound. Upgrading “sweetwaters” from splitting operations in the fatty acid industry requires removal of dissolved salts, elimination of color, and fat and oil impurities, concentration (evaporation of water) and/or distillation. For Twitchellized sweetwaters this generally involves (a.) lime treatment. (b.) filtration, (c.) evaporation to half‐crude, (d.) precipitation of excess lime, (e.) filtration, (f.) evaporation to a concentration of 88–90%, and probably, (g.) distillation. For autoclave or continuous process sweetwaters the upgrading includes (a.) light lime treatment, (b.) filtration, (c.) evaporation concentration to 88–90%, and probably, (d.) distillation. Glycerol may also be upgraded by ion‐exchange processing followed by evaporation concentration in which distillation may be eliminated. Ion‐exclusion (Dow process) is also feasible. Many special triglyceride products are required of different fatty acid homolog distribution than those of the parent or hydrogenated fats and oils. These are prepared by splitting the fats or hydrogenated oils, fractionating the fatty acids, upgrading the glycerol, and recombining the desired fractionated acids with glycerol by reesterification. One example is high lauric triglyceride from coconut oil suited for use as a coco butter substitute.

Removal of Soluble Secondary-Effluent Organics

Data are presented on the removal of soluble organic nitrogen (SON) and soluble chemical oxygen demand (SCOD) by chemical coagulation, activated-carbon adsorption, ion exchange, lime precipitation, chemical oxidation, biological oxidation and various combinations of these processes. This information will enable decision makers to assess the economic impact and technological feasibility of setting limitations on the discharge of organic nitrogen, and will be of use to engineers in designing treatment systems for removal of SON should limitations be imposed. A hypothetical scheme is proposed which operationally fractionates SON and SCOD in a manner defined by the experimental results of the study and by the nature of the processes involved. The scheme divides SON and SCOD into a number of fractions and indicates which are mutually exclusive and which overlap. Such a scheme is helpful in understanding and predicting the behavior of organic contaminants with respect to various treatment processes and fractionates organics.

Charged Membrane Ultrafiltration of Multisalt Systems: Application to Acid Mine Waters

Abstract Ultrafiltration of dissolved and precipitated inorganic salts from synthetic and actual acid mine waters is investigated experimentally in a bench-scale, continuous-flow unit, utilizing negatively charged, noncellulosic membranes. The process is evaluated in terms of the simultaneous achievement of good water flux without membrane fouling and of adequate ultrafiltrate quality at high water recovery for water reuse operation. At a transmembrane pressure of 5.6 X 105 N/m2 and a channel Reynolds number of 6,000, the flux drop is less than 30%, even with a concentrated acid mine water containing 16,000 mg/1 total solids and a high CaSO4 concentration. At 90% ultrafiltrate recovery, depending on the type of noncellulosic membrane utilized, 98% iron removal, 85% aluminum removal, and 50 to 73% calcium and manganese removals can be obtained at an average water flux from 6.4X10−4 to 13.2X10−4 cm/sec. The overall ultrafiltrate quality is considerably better than that observed with a lime precipitation pro...