Optimization of wastewater quality in the Sines refinery

In order to address and resolve the wastewater contamination problem of the Sines refinery with the main objective of optimizing the quality of this stream and reducing the costs charged to the refinery, a dynamic mass balance was developed nd implemented for ammonia and polar oil and grease (O&G) contamination in the wastewater circuit. The inadequate routing of sour gas from the sour water stripping unit and the kerosene caustic washing unit, were identified respectively as the major source of ammonia and polar substances present in the industrial wastewater effluent. For the O&G content, a predictive model was developed for the kerosene caustic washing unit, following the Projection to Latent Structures (PLS) approach. Comparison between analytical data for ammonia and polar O&G concentrations in refinery wastewater originating from the Dissolved Air Flotation (DAF) effluent and the model predictions of the dynamic mass balance calculations are in a very good agreement and highlights the dominant impact of the identified streams for the wastewater contamination levels. The ammonia contamination problem was solved by rerouting the sour gas through an existing clogged line with ammonia salts due to a non-insulated line section, while for the O&G a dynamic mass balance was implemented as an online tool, which allows for prevision of possible contamination situations and taking the required preventive actions, and can also serve as a basis for establishing relationships between the O&G contamination in the refinery wastewater with the properties of the refined crude oils and the process operating conditions. The PLS model developed could be of great asset in both optimizing the existing and designing new refinery wastewater treatment units or reuse schemes. In order to find a possible treatment solution for the spent caustic problem, an on-site pilot plant experiments for NaOH recovery from the refinery kerosene caustic washing unit effluent using an alkaline-resistant nanofiltration (NF) polymeric membrane were performed in order to evaluate its applicability for treating these highly alkaline and contaminated streams. For a constant operating pressure and temperature and adequate operating conditions, 99.9% of oil and grease rejection and 97.7% of chemical oxygen demand (COD) rejection were observed. No noticeable membrane fouling or flux decrease were registered until a volume concentration factor of 3. These results allow for NF permeate reuse instead of fresh caustic and for significant reduction of the wastewater contamination, which can result in savings of 1.5 M€ per year at the current prices for the largest Portuguese oil refinery. The capital investments needed for implementation of the required NF membrane system are less than 10% of those associated with the traditional wet air oxidation solution of the spent caustic problem. The operating costs are very similar, but can be less than half if reusing the NF concentrate in refinery pH control applications. The payback period was estimated to be 1.1 years. Overall, the pilot plant experimental results obtained and the process economic evaluation data indicate a very competitive solution through the proposed NF treatment process, which represents a highly promising alternative to conventional and existing spent caustic treatment units.

An investigation of soil quality parameters relating to agricultural reuse and land disposal options for the management of biosolids

Sludge provides valuable nutrients to soil. Application of sludge to land is subject to a number of limitations. Its use as a soil conditioner represents a "beneficial reuse option". Primary and secondary sludge from Dublin city is treated in Ringsend treatment plant where it undergoes thermal drying. This study investigates the feasibility of land application of thermally dried biosolids (TDB) from Ringsend treatment plant.

Irrigation with domestic wastewater: a multivariate analysis of main soil changes

Irrigation with treated domestic sewage wastewater (TSE) is an agricultural practice to reduce water requirements of agroecossystems and the nutrient load impact on freshwaters, but adverse effects on soil chemical (salinization, sodification, etc.) and soil physical properties (alteration in soil porosity and hydraulic conductivity, etc.) have been reported. This study aimed to define some relationships among these changes in an Oxisol using multivariate analysis. Corn (Zea mays L.) and sunflower (Helianthus annuus L.) were grown for two years, irrigated with TSE. The following soil properties were determined: Ca2+; Mg2+; Na+; K+ and H + Al contents, cationic exchangeable capacity (CEC), sum of bases (SB), base saturation (V), texture (sand, silt and clay), macro-, micro-, and cryptoporosity (V MA, V MI and V CRI), water content at soil saturation (θS) and at field capacity (θFC), residual water content (θR), soil bulk density (d s), water dispersed clay (WDC) and saturated hydraulic conductivity (K SAT). Factor analysis revealed the following six principal factors: Fine Porosity (composed of Na+; K+; WDC, θR, θRFC, and V CRI); Large Porosity (θS, d s, V MA, Vs); Soil CEC (Ca2+; Mg2+; CEC, SB, V); Soil Acidity (H + Al); and Soil Texture (factors 5 and 6). A dual pore structure appears clearly to the factors 1 and 2, with an apparent relationship between fine porosity and the monovalent cations Na+ and K+. The irrigation (with potable sodic tap water or sewage wastewater) only had a significant effect on Fine Porosity and Large Porosity factors, while factors 3 and 4 (Soil CEC and Soil Acidity) were correlated with soil depth. The main conclusion was a shift in pore distribution (large to fine pores) during irrigation with TSE, which induces an increase of water storage and reduces the capacity of drainage of salts.

Water-dispersible clay in soils treated with sewage sludge

A by-product of Wastewater Treatment Stations is sewage sludge. By treatment and processing, the sludge is made suitable for rational and environmentally safe use in agriculture. The aim of this study was to assess the influence of different doses of limed sewage sludge (50 %) on clay dispersion in soil samples with different textures (clayey and medium). The study was conducted with soil samples collected from native forest, on a Red Latosol (Brazilian classification: Latossolo Vermelho distroférrico) loamy soil in Londrina (PR) and a Red-Yellow Latosol (BC: Latossolo Vermelho-Amarelo distrófico) medium texture soil in Jaguapitã (PR). Pots were filled with 3 kg of air-dried fine earth and kept in greenhouse. The experiment was arranged in a randomized block design with six treatments: T1 control, and treatments with limed sewage sludge (50 %) as follows: T2 (3 t ha-1), T3 (6 t ha-1), T4 (12 t ha-1), T5 (24 t ha-1) and T6 (48 t ha-1) and five replications. The incubation time was 180 days. At the end of this period, the pots were opened and two sub-samples per treatment collected to determine pH-H2O, pH KCl (1 mol L-1), organic matter content, water-dispersible clay, ΔpH (pH KCl - pH-H2O) and estimated PZC (point of zero charge): PZC = 2 pH KCl - pH-H2O, as well as the mineralogy of the clay fraction, determined by X ray diffraction. The results showed no significant difference in the average values for water-dispersible clay between the control and the other treatments for the two soil samples studied and ΔpH was the variable that correlated best with water-dispersible clay in both soils.

Electrical conductivity of soil irrigated with swine wastewater estimated by time-domain reflectometry¹

Wastewater application to soil is an alternative for fertilization and water reuse. However, particular care must be taken with this practice, since successive wastewater applications can cause soil salinization. Time-domain reflectometry (TDR) allows for the simultaneous and continuous monitoring of both soil water content and apparent electrical conductivity and thus for the indirect measurement of the electrical conductivity of the soil solution. This study aimed to evaluate the suitability of TDR for the indirect determination of the electrical conductivity (ECse) of the saturated soil extract by using an empirical equation for the apparatus TDR Trase 6050X1. Disturbed soil samples saturated with swine wastewater were used, at soil proportions of 0, 0.45, 0.90, 1.80, 2.70, and 3.60 m³ m-3. The probes were equipped with three handmade 0.20 cm long rods. The fit of the empirical model that associated the TDR measured values of electrical conductivity (EC TDR) to ECse was excellent, indicating this approach as suitable for the determination of electrical conductivity of the soil solution.

Reuse of Lime Sludge from Water Softening and Coal Combustion Byproducts, TR-459, 2004

Disposal of lime sludge remains a major challenge to cities in the Midwest. Disposal of lime sludge from water softening adds about 7-10% to the cost of water treatment. Having effective and safe options is essential for future compliance with the regulations of the State of Iowa and within budget restrictions. Dewatering and drying are essential to all reuse applications as this affects transportation costs and utility. Feasibility tests were conducted on some promising applications like SOx control in power generation facilities that burn coal, replacement of limestone as an ingredient in portland cement production, dust control on gravel roads, neutralization of industrial wastewater pH, and combination with fly ash or cement in construction fill applications. A detailed report and analysis of the construction fills application is presented in the second half of the report. A brief discussion of the results directly follows.

Applications for Reuse of Lime Sludge from Water Softening, TR-535, 2005

Lime sludge, an inert material mostly composed of calcium carbonate, is the result of softening hard water for distribution as drinking water. A large city such as Des Moines, Iowa, produces about 30,700 tons of lime sludge (dry weight basis) annually (Jones et al., 2005). Eight Iowa cities representing, according to the United States (U.S.) Census Bureau, 23% of the state’s population of 3 million, were surveyed. They estimated that they collectively produce 64,470 tons of lime sludge (dry weight basis) per year, and they currently have 371,800 tons (dry weight basis) stockpiled. Recently, the Iowa Department of Natural Resources directed those cities using lime softening in drinking water treatment to stop digging new lagoons to dispose of lime sludge. Five Iowa cities with stockpiles of lime sludge funded this research. The research goal was to find useful and economical alternatives for the use of lime sludge. Feasibility studies tested the efficacy of using lime sludge in cement production, power plant SOx treatment, dust control on gravel roads, wastewater neutralization, and in-fill materials for road construction. Applications using lime sludge in cement production, power plant SOx treatment, and wastewater neutralization, and as a fill material for road construction showed positive results, but the dust control application did not. Since the fill material application showed the most promise in accomplishing the project’s goal within the time limits of this research project, it was chosen for further investigation. Lime sludge is classified as inorganic silt with low plasticity. Since it only has an unconfined compressive strength of approximately 110 kPa, mixtures with fly ash and cement were developed to obtain higher strengths. When fly ash was added at a rate of 50% of the dry weight of the lime sludge, the unconfined strength increased to 1600 kPa. Further, friction angles and California Bearing Ratios were higher than those published for soils of the same classification. However, the mixtures do not perform well in durability tests. The mixtures tested did not survive 12 cycles of freezing and thawing and wetting and drying without excessive mass and volume loss. Thus, these mixtures must be placed at depths below the freezing line in the soil profile. The results demonstrated that chemically stabilized lime sludge is able to contribute bulk volume to embankments in road construction projects.

Haja-asutusalueiden sakokaivolietteiden kalkkistabilointi ja hyötykäyttö maataloudessa

In the sparsely populated areas of Finland there are approximately 350 000 households and 450 000 leisure time residences outside sewer networks. According to the Finnish domestic wastewater act outside sewer networks, the Finnish Government is reducing the environmental load of domestic wastewaters by the year 2017. The law is aimed at restricting the quality of sludge from domestic wastewater purification systems. The wastewater purification systems are complex systems, which often include sedimentation basins. The sedimentation basins remove most of the nutrients from the domestic wastewaters. The Finnish Government has decided that sedimentation basin sludge must be treated before reusing. One possibility is to stabilise domestic sludge with slaked lime and to reuse treated sludge in agriculture. According to this master’s thesis lime stabilisation can be done in sedimentation basins or in decanting tanks. Decanting tanks must be under 100 m3. Dosage of stabilisation is 8,5 kg/m3 of lime. If you are treading sludge that is highly hydrous, you need 13,5 kg/m3 of lime. In stabilisation lime and sludge must be thoroughly mixed. Mixed sludge must be in sedimentation basin at least two hours. If there is evidence that sludge contains salmonella or if it’s decanting tank stabilisation time is 48 hours. Sludge must be mixed at least once during the longer stabilisation time. Lime destroys Esherichia coli and enterococcus concentrations below accepted level. Lime also destroys Salmonella bacterium. After treating, sludge’s can be distributed over a field. You can safely spread lime treated domestic sludge’s about 40 m3/ha. Lime stabilisation can also be used to treat separately and collectively collected domestic wastewaters.

Pastalietteen hyödyntäminen raaka-aineena.

Pastalietettä syntyy metsäteollisuudessa päällystettyä paperia ja kartonkia valmistavissa yksiköissä, joissa on pastapitoisten vesien erilliskäsittely. Pastalietettä syntyi Suomessa vuonna 1998 noin 50 000 tw. Pastapitoisille vesille on kehitetty käsittelymenetelmiä, joilla pasta voidaan kierrättää takaisin prosessiin. Näistä menetelmistä mainittakoon ultrasuodatus, joka on jo käytössä eräillä tehtailla, sekä dispergointi-menetelmä, joka on pastalietteen osalta koekäyttöasteella. Pastalietteen soveltuvuutta sorateiden kulutuskerrosmateriaaliksi tutkittiin alustavasti koelaatikoin ja laboratoriokokein. Pastalietteellä on näiden tutkimusten mukaan murskeen tiivistyvyyttä parantavia ominaisuuksia. Koelaatikoista sitoutumista ja käyttäytymistä sään vaihdellessa on seurattu silmämääräisesti ja alustavat arviot ovat varovaisen lupaavia Pastalietteen arvioitu menekki on 37 t/km, jolloin koko Suomessa syntyvällä pastalietemäärällä voitaisiin käsitellä 1 350 soratiekilometriä Kuivatun pastalietteen käyttöä kiviainesteollisuuden raaka-aineeksi on kartoitettu tiilen, kevytsoran ja vuorivillan valmistuksessa. Tiilen valmistuksessa pastalietettä on jo käytetty, tulokset ovat olleet vaihtelevia. Pastalietteen hyötykäyttöpotentiaalia nykyisillä tiilitehtailla on arvioiden mukaan 15 000 t/a. Käyttö kevytsoran ja vuorivillan valmistuksessa vaatisi lisätutkimuksia

Treatment of micropollutants in municipal wastewater: study of a sequential batch biofilter

All the experimental part of this final project was done at Laboratoire de Biotechnologie Environnementale (LBE) from the École Polytechnique Fédérale de Lausanne (EPFL), Switzerland, during 6 months (November 2013- May 2014). A fungal biofilter composed of woodchips was designed in order to remove micropollutants from the effluents of waste water treatment plants. Two fungi were tested: Pleurotus ostreatus and Trametes versicolor in order to evaluate their efficiency for the removal of two micropollutants: the anti-inflammatory drug naproxen and the antibiotic sulfamethoxazole,. Although Trametes versicolor was able to degrade quickly naproxen, this fungus was not any more active after one week of operation in the filter. Pleurotus ostreatus was, on contrary, able to survive more than 3 months in the filter, showing good removal efficiencies of naproxen and sulfamethoxazole during all this period, in tap water but also in real treated municipal wastewater. Several other experiments have provided insight on the removal mechanisms of these micropollutants in the fungal biofilter (degradation and adsorption) and also allowed to model the removal trend. Fungal treatment with Pleurotus ostreatus grown on wood substrates appeared to be a promising solution to improve micropollutants removal in wastewater.

Treatment of oily wastewater by ultrafiltration: The effect of different operating and solution conditions

In many industries, such as petroleum production, and the petrochemical, metal, food and cosmetics industries, wastewaters containing an emulsion of oil in water are often produced. The emulsions consist of water (up to 90%), oils (mineral, animal, vegetable and synthetic), surfactants and other contaminates. In view of its toxic nature and its deleterious effects on the surrounding environment (soil, water) such wastewater needs to be treated before release into natural water ways. Membrane-based processes have successfully been applied in industrial applications and are considered as possible candidates for the treatment of oily wastewaters. Easy operation, lower cost, and in some cases, the ability to reduce contaminants below existing pollution limits are the main advantages of these systems. The main drawback of membranes is flux decline due tofouling and concentration polarisation. The complexity of oil-containing systems demands complementary studies on issues related to the mitigation of fouling and concentration polarisation in membranebased ultrafiltration. In this thesis the effect of different operating conditions (factors) on ultrafiltration of oily water is studied. Important factors are normally correlated and, therefore, their effect should be studied simultaneously. This work uses a novel approach to study different operating conditions, like pressure, flow velocity, and temperature, and solution properties, like oil concentration (cutting oil, diesel, kerosene), pH, and salt concentration (CaCl2 and NaCl)) in the ultrafiltration of oily water, simultaneously and in a systematic way using an experimental design approach. A hypothesis is developed to describe the interaction between the oil drops, salt and the membrane surface. The optimum conditions for ultrafiltration and the contribution of each factor in the ultrafiltration of oily water are evaluated. It is found that the effect on permeate flux of the various factors studied strongly depended on the type of oil, the type of membrane and the amount of salts. The thesis demonstrates that a system containing oil is very complex, and that fouling and flux decline can be observed even at very low pressures. This means that only the weak form of the critical flux exists for such systems. The cleaning of the fouled membranes and the influence of different parameters (flow velocity, temperature, time, pressure, and chemical concentration (SDS, NaOH)) were evaluated in this study. It was observed that fouling, and consequently cleaning, behaved differently for the studied membranes. Of the membranes studied, the membrane with the lowest propensity for fouling and the most easily cleaned was the regenerated cellulose membrane (C100H). In order to get more information about the interaction between the membrane and the components of the emulsion, a streaming potential study was performed on the membrane. The experiments were carried out at different pH and oil concentration. It was seen that oily water changed the surface charge of the membrane significantly. The surface charge and the streaming potential during different stages of filtration were measured and analysed being a new method for fouling of oil in this thesis. The surface charge varied in different stages of filtration. It was found that the surface charge of a cleaned membrane was not the same as initially; however, the permeability was equal to that of a virgin membrane. The effect of filtration mode was studied by performing the filtration in both cross-flow and deadend mode. The effect of salt on performance was considered in both studies. It was found that salt decreased the permeate flux even at low concentration. To test the effect of hydrophilicity change, the commercial membranes used in this thesis were modified by grafting (PNIPAAm) on their surfaces. A new technique (corona treatment) was used for this modification. The effect of modification on permeate flux and retention was evaluated. The modified membranes changed their pore size around 33oC resulting in different retention and permeability. The obtained results in this thesis can be applied to optimise the operation of a membrane plant under normal or shock conditions or to modify the process such that it becomes more efficient or effective.

New strategies for treatment and reuse of spent sulfidic caustic stream from petroleum industry

This work examines traditional and new routes for removal of H2S and other sulfur compounds from spent sufidic caustic (SSC). SH- (hydrogenosulfide) and S2- (sulfide) ions were quantitatively oxidized at 25 ºC using H2O2, NaOCl or a spent sulfochromic mixture. SH-/S2- ions were also removed via reaction with freshly prepared iron or manganese hydroxides, or after passing the SSC through strong basic anion exchange resins (OH- form). The treated caustic solution, as well as iron/manganese hydroxides, removed H2S from diesel samples at 25 ºC. SSC treatment via strong basic anion-exchange resins produced the treated caustic solution with the highest free alkalinity.

Treated domestic sewage: kinetics of Escherichia coli and total coliform inactivation by oxidation with hydrogen peroxide

Hydrogen peroxide has been used for decades in developed countries as an oxidizing agent in the treatment of water, domestic sewage and industrial effluents. This study evaluated the influence of the concentration of H2O2 and pH on the inactivation of Escherichia coli cells and the disinfection of sewage treated. The results showed that the inactivation rate increased with pH and H2O2. The presence of other contaminants dissolved in the effluent is probably the cause of these differences, because E. coli inactivation in synthetic wastewater was found to be much faster than in the real treated domestic sewage.

Use of botanical extracts, cassava wastewater and nematicide for the control of root-knot nematode on carrot

Aqueous extracts of several plant species have shown promising in controlling root-knot nematode, Meloidogyne incognita (Kofoid & White), one of the most limiting agents for carrot cultivation. The current study evaluated the effect of aqueous extracts from seven botanical species applied to 40, 50, 60, 70 and 80 days after sowing 'Nantes' carrots in soil infested with root-knot nematode. Three other treatments included cassava wastewater, distilled water (control), which were applied in the same periods of the extracts application, in addition to carbofuran 50G (80Kg/ha), which was applied once at 60 days after carrot sowing. Evaluations were performed at 90 days after inoculation to determine shoot and root fresh weight, as well as the diameter and the length of principal roots and the number of galls on primary and secondary roots. Plants treated with cassava wastewater, extracts of Ricinus communis L. seeds, Crotalaria juncea L. seeds, R. communis leaves + branches + fruits, Chenopodium ambrosioides L. leaves + branches + inflorescences and Azadirachta indica A. Juss. seeds showed the highest rates of total weight (root + shoot) and shoot weight. The extract of R. communis leaves + branches + fruits provides the highest total root weight and principal root diameter. Cassava wastewater and extracts of R. communis seeds provided the highest principal root weight. The extract of R. communis seeds and cassava wastewater can be considered promising for the alternative control of M. incognita.

Swine wastewater associated with mineral fertilization on corn crop (Zea mays)

This study aimed to evaluate the agronomical and environmental aspects in corn, soil characteristics and leachate resulting from the material combination of swine wastewater and mineral fertilizer in the long run. The experimental area has a history of swine wastewater application for experiments conducted since 2006, this being the seventh crop cycle in the area. Four doses of swine wastewater (0; 100; 200 and 300 m³ ha-1) associated with presence and absence of mineral fertilizer were applied, consisting of eight treatments. The results obtained were subjected to variance analysis and means compared by Tukey test at 5% significance. We conclude that the swine wastewater can be partially used as an alternative fertilizer, since the P and Mn are complemented with specific fertilization. There must be carefulness about Fe+2, Cu+2 and Zn+2 accumulation in soil, and also to the concentrations of Fe+2, Cu+2, Zn+2, NO3- + NO2- and Na+ in leachate which exceeded the limits at the highest SWW applied levels.