The oxygenation in biological wastewater treatment of pulp and paper industry

The UPM-Kymmene Oyj Pietarsaari pulp and paper Mill biological wastewater treatment plant was built in the 1980's and the plant has been in use ever since. During the past years there have been problems with deviations. The wastewater treatment plant needs update, especially the aeration basin, where the old surface aerators cannot produce enough mixing and indroduce oxygen enough to the wastewater. In this thesis how extra aeration with oxygen affects the wastewater treatment plant effluent was studied. In the literature part the main focus is in aeration devices, which can be used in biological wastewater treatment. The target is to compare different kind of aerators, which are suitable for pulp and paper wastewater treatment. Studies show, that EDI-aerators are commonly used and also most suitable. In the experimental part, the focus is on the Pietarsaari Mills wastewater treatment plant and oxygen aeration during autumn 2008. This thesis presents the results of the trial run. Studies show, that extra oxygen devices can produce lot a of mixing and the oxygenation capacity was more than what the micro-organisms needed. The effect on sludge quality could not been seen during the trial runs.

The Methods of Possible Joint Treatment of Manure and Sewage Sludge in the Leningrad Region

The nutrient load to the Gulf of Finland has started to increase as a result of the strong economic recovery in agriculture and livestock farming in the Leningrad region. Also sludge produced from municipal wastewater treatment plant of the Leningrad region causes the great impact on the environment, but still the main options for its treatment is disposal on the sludge beds or Landfills. The aim of this study was to evaluate the implementation of possible joint treatment methods of manure form livestock and poultry enterprises and sewage sludge produced from municipal wastewater treatment plants in the Leningrad region. The study is based on published data. The most attention was put on the anaerobic digestion and incineration methods. The manure and sewage sludge generation for the whole Leningrad region and energy potential produced from their treatment were estimated. The calculations showed that total amount of sewage sludge generation is 1 348 000 t/a calculated on wet matter and manure generation is 3 445 000 t/a calculated on wet matter. The potential heat release from anaerobic digestion process and incineration process is 4 880 000 GJ/a and 5 950 000 GJ/a, respectively. Furthermore, the work gives the overview of the general Russian and Finnish legislation concerning manure and sewage sludge treatment. In the Gatchina district it was chosen the WWTP and livestock and poultry enterprises for evaluation of the centralized treatment plant implementation based on anaerobic digestion and incineration methods. The electricity and heat power of plant based on biogas combustion process is 4.3 MW and 7.8 MW, respectively. The electricity and heat power of plant based on manure and sewage sludge incineration process is 3.0 MW and 6.1 MW, respectively.

Sewage Sludge Electro-Dewatering

Original sludge from wastewater treatment plants (WWTPs) usually has a poor dewaterability. Conventionally, mechanical dewatering methods are used to increase the dry solids (DS) content of the sludge. However, sludge dewatering is an important economic factor in the operation of WWTPs, high water content in the final sludge cake is commonly related to an increase in transport and disposal costs. Electro‐dewatering could be a potential technique to reduce the water content of the final sludge cake, but the parameters affecting the performance of electro‐dewatering and the quality of the resulting sludge cake, as well as removed water, are not sufficiently well known. In this research, non‐pressure and pressure‐driven experiments were set up to investigate the effect of various parameters and experimental strategies on electro‐dewatering. Migration behaviour of organic compounds and metals was also studied. Application of electrical field significantly improved the dewatering performance in comparison to experiments without electric field. Electro‐dewatering increased the DS content of the sludge from 15% to 40 % in non‐pressure applications and from 8% to 41% in pressure‐driven applications. DS contents were significantly higher than typically obtained with mechanical dewatering techniques in wastewater treatment plant. The better performance of the pressure‐driven dewatering was associated to a higher current density at the beginning and higher electric field strength later on in the experiments. The applied voltage was one of the major parameters affecting dewatering time, water removal rate and DS content of the sludge cake. By decreasing the sludge loading rate, higher electrical field strength was established between the electrodes, which has a positive effect on an increase in DS content of the final sludge cake. However interrupted voltage application had anegative impact on dewatering in this study, probably because the off‐times were too long. Other factors affecting dewatering performance were associated to the original sludge characteristics and sludge conditioning. Anaerobic digestion of the sludge with high pH buffering capacity, polymer addition and freeze/thaw conditioning had a positive impact on dewatering. The impact of pH on electro‐dewatering was related to the surface charge of the particles measured as zeta‐potential. One of the differences between electro‐dewatering and mechanical dewatering technologies is that electro‐dewatering actively removes ionic compounds from the sludge. In this study, dissolution and migration of organic compounds (such as shortchain fatty acids), macro metals (Na, K, Ca, Mg, Fe) and trace metals (Ni, Mn, Zn, Cr) was investigated. The migration of the metals depended on the fractionation and electrical field strength. These compounds may have both negative and positive impacts on the reuse and recycling of the sludge and removed water. Based on the experimental results of this study, electro‐dewatering process can be optimized in terms of dewatering time, desired DS content, power consumption and chemical usage.

Lannoitetehtaan prosessivesien käsittelyvaihtoehtojen soveltuvuuden arviointi

Phosphorus and nitrogen cause eutrophication of water bodies, causing severe damage to the ecosystem. Eutrophication of the waters causes oxygen depletion, which in turn increases fish mortality, releasing toxins in waters. The released toxins can cause damage to animals and humans, which is the reason in many countries to set emission limits for waste water. Nutrients exist naturally, but due to human activities there is high nutrient leaching to water bodies. Human activity is one of the main reasons to the eutrophication. The aim of this thesis was to estimate the suitability of different water treatment options for Yara Finland’s fertilizer plant’s process waters in Siilinjärvi. The fertilizer plant process waters are high concentrate and especially nitrogen concentrations are high, which bring challenge to the treatment. At the theoretical part was investigated conventional and as well advanced wastewater treatment methods like reverse osmosis, adsorption and ion exchange. Beside different treatment methods corporate environmental requirements, responsibility and strategies were researched. At the empirical part of the thesis the goal was to find out possibil-ities to intensify the efficiency of purification at lamella clarifier with chemical precipitation. In addition possibility to use already existing chemical purifying plant for process waters was estimated. As a result of the research Yara has a possibility to intensify lamella clarifier’s action by addi-tion of calcium hydroxide and thus to obtain the phosphorus and fluorine to precipitate out of the water. But in practice this would be too expensive. It is possible to eliminate nitrogen compounds by adsorption or ammonia stripping, both methods requires additional testing. It is possible to process waters in chemical purifying plant, if ammonium nitrogen has been reduced before. Reverse osmosis is possible to exploit for the phosphoric acid plant’s waters.

Evaluation of the effect of the seed extract of Moringa oleifera Lam over the efficiency of organic filters in wastewater treatment of dairy cattle breeding

This study aimed to evaluate the effect of Moringa oleifera Lam extract on the removal of total solids (TS), total suspended solids (TSS) and chemical oxygen demand (COD), in different filter media for treating wastewater of dairy cattle breeding (DCW). The moringa seed extract was obtained by grinding 50 g of seeds in one liter of distilled water and, after passing the solution through a quantitative paper filter of 25 microns, 60 mL of the extract were added to wastewater from cattle breeding before the filtration process in organic filters made of thin coal, bamboo leaves, eucalyptus leaves, gliricidia branches and sawdust. This was followed by the completely randomized experimental design, adopting a factorial of 5 x 2. Aliquots of filtered effluent were collected and the total solids (TS) concentrations, total suspended solids (TSS) and chemical oxygen demand (COD) were determined. It was found that the increase in the efficiency of removal of COD and total solids can be attributed to the coagulating power of the moringa seed extract, wherein the filter medium with bamboo leaves presented the best performance, showing potential for use as alternative filter material in the primary treatment of DCW.

Soil physical attributes in chemigated banana plantation with wastewater

ABSTRACT The feasibility of using sewage wastewater as a water and nutrient source for plants is an alternative to harness agricultural natural resource, observing its influence on the organic matter dynamics and soil energy. Our objective here was to evaluate the effects of applying different doses of effluent from a sewage treatment plant, in Janaúba – MG, Brazil, over the physical attributes of a soil grown with “Prata Anã” banana. From soil sample collection at depths of 0-20, 20-40, and 40-60 cm, we determined the following soil properties: soil density, total porosity, macroporosity, microporosity, organic matter, clay dispersed in water and stability of soil aggregate. The experimental design was in randomized blocks with four repetitions. Wastewater raising doses promoted increase in suspended solids, contributing to macroporosity reduction at 20-40 and 40-60 cm depths; as well as a reduction in organic matter within 0-20 cm layer. Clay dispersal was observed in the depths of 0-20 cm, being derived from an increase in sodium content. Concurrently, there was a reduction of soil aggregate stability.

Käytetyn voiteluöljyn regenerointilaitoksen prosessivesien karakterisointi

Käytetyn voiteluöljyn regeneroinnissa muodostuu prosessivettä useista lähteistä. Tehokas päästöjenhallinta on yksi tärkeimmistä tavoitteista regenerointilaitoksen operoinnissa ja sen takia sitä tulee kehittää jatkuvasti entistä paremmaksi. Tavoitteisiin pääsemiseksi on oleellista tunnistaa vesienkäsittelyprosessin laadullinen massatase ja laadunvaihtelut ajotilanteiden mukaan. Työssä tutkitaan ja analysoidaan veden sisältämiä epäpuhtauksia sekä kirjallisuuslähteiden perusteella, että standardimenetelmillä ja modifioiduilla menetelmillä, joilla on akkreditointi. Analyysituloksista muodostetaan laadullinen massatase, josta nähdään epäpuhtauksien ja niitä kuvaavien parametrien kuormitukset kussakin prosessivesivirrassa. Tulosten perusteella arvioidaan nykyisen vesienkäsittelyn tehokkuutta, sen säätömahdollisuuksia ja kehitystarvetta. Tarkastelun ulkopuolelle kuitenkin jätetään vesienkäsittelystä ulosjohdettavan prosessiveden puhdistuslaitos. Tutkimusten perusteella regenerointilaitoksessa muodostuvien prosessivesien epäpuhtaudet koostuvat öljystä, BTEX-yhdisteistä, fenoliyhdisteistä, liuottimista, polttoaineiden ja voiteluöljyjen lisäaineista, typpi- ja rikkiyhdisteistä, metalliyhdisteistä sekä kiintoaineesta. Öljy jakautuu kevyisiin (C5-C10), keskiraskaisiin (C10-21) ja raskaisiin (C21-40) jakeisiin. Vesienkäsittelyssä suurin osa öljystä ja epäpuhtauksista saadaan erottumaan vedestä, jolloin puhdistuslaitokselle päätyy jäämäpitoisuudet öljyä, haihtuvia yhdisteitä sekä muita epäpuhtauksia. Puhdistuslaitosta kuormittavat eniten liuenneet orgaaniset yhdisteet sekä korkeaa kemiallista hapenkulutusta aiheuttavat epäorgaaniset yhdisteet (suolat), joiden erottamista prosessivesistä on syytä tulevaisuudessa kehittää.

Electro-Oxidation Treatment of Pulp and Paper Mill Circulating Waters and Wastewaters

Interest in water treatment by electrochemical methods has grown in recent years. Electrochemical oxidation has been applied particularly successfully to degrade different organic pollutants and disinfect drinking water. This study summarizes the effectiveness of the electrochemical oxidation technique in inactivating different primary biofilm forming paper mill bacteria as well as sulphide and organic material in pulp and paper mill wastewater in laboratory scale batch experiments. Three different electrodes, borondoped diamond (BDD), mixed metal oxide (MMO) and PbO2, were employed as anodes. The impact on inactivation efficiency of parameters such as current density and initial pH or chloride concentration of synthetic paper machine water was studied. The electrochemical behaviour of the electrodes was investigated by cyclic voltammetry with MMO, BDD and PbO2 electrodes in synthetic paper mill water as also with MMO and stainless steel electrodes with biocides. Some suggestions on the formation of different oxidants and oxidation mechanisms were also presented during the treatment. Aerobic paper mill bacteria species (Deinococcus geothermalis, Pseudoxanthomonas taiwanensis and Meiothermus silvanus) were inactivated effectively (>2 log) at MMO electrodes by current density of 50 mA/cm2 and the time taken three minutes. Increasing current density and initial chloride concentration of paper mill water increased the inactivation rate of Deinococcus geothermalis. The inactivation order of different bacteria species was Meiothermus silvanus > Pseudoxanthomonas taiwanensis > Deinococcus geothermalis. It was observed that inactivation was mainly due to the electrochemically generated chlorine/hypochlorite from chloride present in the water and also residual disinfection by chlorine/hypochlorite occurred. In real paper mill effluent treatment sulphide oxidation was effective with all the different initial concentrations (almost 100% reduction, current density 42.9 mA/cm2) and also anaerobic bacteria inactivation was observed (almost 90% reduction by chloride concentration of 164 mg/L and current density of 42.9 mA/cm2 in five minutes). Organic material removal was not as effective when comparing with other tested techniques, probably due to the relatively low treatment times. Cyclic voltammograms in synthetic paper mill water with stainless steel electrode showed that H2O2 could be degraded to radicals during the cathodic runs. This emphasises strong potential of combined electrochemical treatment with this biocide in bacteria inactivation in paper mill environments.

Hydrometallurgical recovery of valuable metals from secondary raw materials

Wastes and side streams in the mining industry and different anthropogenic wastes often contain valuable metals in such concentrations their recovery may be economically viable. These raw materials are collectively called secondary raw materials. The recovery of metals from these materials is also environmentally favorable, since many of the metals, for example heavy metals, are hazardous to the environment. This has been noticed in legislative bodies, and strict regulations for handling both mining and anthropogenic wastes have been developed, mainly in the last decade. In the mining and metallurgy industry, important secondary raw materials include, for example, steelmaking dusts (recoverable metals e.g. Zn and Mo), zinc plant residues (Ag, Au, Ga, Ge, In) and waste slurry from Bayer process alumina production (Ga, REE, Ti, V). From anthropogenic wastes, waste electrical and electronic equipment (WEEE), among them LCD screens and fluorescent lamps, are clearly the most important from a metals recovery point of view. Metals that are commonly recovered from WEEE include, for example, Ag, Au, Cu, Pd and Pt. In LCD screens indium, and in fluorescent lamps, REEs, are possible target metals. Hydrometallurgical processing routes are highly suitable for the treatment of complex and/or low grade raw materials, as secondary raw materials often are. These solid or liquid raw materials often contain large amounts of base metals, for example. Thus, in order to recover valuable metals, with small concentrations, highly selective separation methods, such as hydrometallurgical routes, are needed. In addition, hydrometallurgical processes are also seen as more environmental friendly, and they have lower energy consumption, when compared to pyrometallurgical processes. In this thesis, solvent extraction and ion exchange are the most important hydrometallurgical separation methods studied. Solvent extraction is a mainstream unit operation in the metallurgical industry for all kinds of metals, but for ion exchange, practical applications are not as widespread. However, ion exchange is known to be particularly suitable for dilute feed solutions and complex separation tasks, which makes it a viable option, especially for processing secondary raw materials. Recovering valuable metals was studied with five different raw materials, which included liquid and solid side streams from metallurgical industries and WEEE. Recovery of high purity (99.7%) In, from LCD screens, was achieved by leaching with H2SO4, extracting In and Sn to D2EHPA, and selectively stripping In to HCl. In was also concentrated in the solvent extraction stage from 44 mg/L to 6.5 g/L. Ge was recovered as a side product from two different base metal process liquors with Nmethylglucamine functional chelating ion exchange resin (IRA-743). Based on equilibrium and dynamic modeling, a mechanism for this moderately complex adsorption process was suggested. Eu and Y were leached with high yields (91 and 83%) by 2 M H2SO4 from a fluorescent lamp precipitate of waste treatment plant. The waste also contained significant amounts of other REEs such as Gd and Tb, but these were not leached with common mineral acids in ambient conditions. Zn was selectively leached over Fe from steelmaking dusts with a controlled acidic leaching method, in which the pH did not go below, but was held close as possible to, 3. Mo was also present in the other studied dust, and was leached with pure water more effectively than with the acidic methods. Good yield and selectivity in the solvent extraction of Zn was achieved by D2EHPA. However, Fe needs to be eliminated in advance, either by the controlled leaching method or, for example, by precipitation. 100% Pure Mo/Cr product was achieved with quaternary ammonium salt (Aliquat 336) directly from the water leachate, without pH adjustment (pH 13.7). A Mo/Cr mixture was also obtained from H2SO4 leachates with hydroxyoxime LIX 84-I and trioctylamine (TOA), but the purities were 70% at most. However with Aliquat 336, again an over 99% pure mixture was obtained. High selectivity for Mo over Cr was not achieved with any of the studied reagents. Ag-NaCl solution was purified from divalent impurity metals by aminomethylphosphonium functional Lewatit TP-260 ion exchange resin. A novel preconditioning method, named controlled partial neutralization, with conjugate bases of weak organic acids, was used to control the pH in the column to avoid capacity losses or precipitations. Counter-current SMB was shown to be a better process configuration than either batch column operation or the cross-current operation conventionally used in the metallurgical industry. The raw materials used in this thesis were also evaluated from an economic point of view, and the precipitate from a waste fluorescent lamp treatment process was clearly shown to be the most promising.

Treatment of Fe-containing Acid Mine Waters in Fixed Bed Adsorption Column with Calcite Side-Stone

The acid mining drainage is considered the most significant environmental pollution problem around the world for the extensive formation acidic leachates containing heavy metals. Adsorption is widely used methods in water treatment due to it easy operation and the availability of a wide variety of commercial adsorbent (low cost). The primary goal of this thesis was to investigate the efficiency of neutralizing agents, CaCO3 and CaSiO3, and metal adsorption materials with unmodified limestone from Company Nordkalk Oy. In addition to this, the side materials of limestone mining were tested for iron adsorption from acidic model solution. This study was executed at Lappeenranta University of Technology, Finland. The work utilised fixed-bed adsorption column as the main equipment and large fluidized column. Atomic absorption spectroscopy (AAS) and x-ray diffraction (XRD) was used to determine ferric removal and the composition of material respectively. The results suggest a high potential for the studied materials to be used a low cost adsorbents in acid mine drainage treatment. From the two studied adsorbents, the FS material was more suitable than the Gotland material. Based on the findings, it is recommended that further studies might include detailed analysis of Gotland materials.

Water relations of tree species growing on a rock outcrop in the "Parque Estadual de Itapuã", RS

Water relations of the tree species Myrsine umbellata Mart. ex A. DC., Dodonaea viscosa Jacq. and Erythroxylum argentinum O. E. Schulz, growing on a rock outcrop in the "Parque Estadual de Itapuã" (RS), were studied. Environmental (precipitation, temperature, soil water) and plant (water potential, vapor pressure deficit, stomatal conductance, transpiration, leaf specific hydraulic conductance, osmotic potential and cell wall elasticity) parameters were collected in five periods and pooled into two sets of data: wet and dry periods. Myrsine umbellata showed great stability of the plant parameters, including the maintenance of high pre-dawn (psiwpd) and mid-day (psiwmd) water potentials in the dry period (-0.48 and -1.12 MPa, respectively), suggesting the presence of a deep root system. Dodonaea viscosa and E. argentinum reached lower psiwpd (-1.41 and -1.97 MPa, respectively) and a greater degree of stomatal closure in the dry period, suggesting a shallower root system. Differential exposure to soil drought was also corroborated by differential drought effects on the whole-plant leaf specific hydraulic conductance (Gt). Correlation analysis pointed to weak correlations between psiwpd and g s. Erythroxylum argentinum was the only species to show osmotic adjustment in response to drought. It is suggested that M. umbellata has low tolerance to water deficits, adopting an avoidance behavior. The much lower values of psiw reached by D. viscosa and E. argentinum suggest a greater tolerance to drought by these species.

Talousvesilaitoksen saostusvaiheen tehostaminen esihapetuksella – Case Suomen Sokeri Oy:n vedenkäsittely

Diplomityö tehtiin Suomen Sokeri Oy:n vesilaitokselle Vihreän Kemian laboratoriossa. Prosessia tarkasteltiin saostuksen osalta ja tavoitteena oli sen kehittäminen esihapetusmenetelmän tai saostuskemikaalin vaihdon avulla. Tarkastelu tehtiin orgaanisen, kiintoaineksen ja metallien poiston, desinfiointitehon sekä ympäristöystävällisyyden osalta. Potentiaalisia esihapetusmenetelmiä (kaliumpermanganaatti, vetyperoksidi, valokemiallinen, H2O2/UV, valokatalyyttinen, TiO2/UV, H2O2/ultraääni sekä esihapetus peretikkahapolla) tarkasteltiin eri pitoisuuksilla ja tehoilla laboratoriomittakaavassa jar-testin avulla. Saostustehoa testattiin alumiinikloridilla ja ferrisulfaatilla. Raakaveden laadun muutoksia eri vaiheissa seurattiin laboratorioanalyysein. Hapetusmenetelmien desinfiointiteho, vaikutukset syanobakteereihin ja -toksiineihin sekä reaktioissa syntyvät sivutuotteet kartoitettiin teorian perusteella. Työn tuloksien perusteella kaliumpermanganatti, vetyperoksidi erityisesti kehittyneenä hapetustekniikkana sekä valokatalyyttinen menetelmä tehostivat vedenkäsittelyä, mutta koska TiO2/UV- tai ultraäänihapetukselle ei ole vielä olemassa kaupallista sovellusta laitosmittakaavassa niin suositeltavat menetelmät ovat KMnO4- ja H2O2(/UV)-hapetukset jatkotutkimussuositukset huomioiden. Peretikkahappo ei tämän tutkimuksen perusteella vaikuttanut suositeltavalta hapetusmenetelmältä, mutta sen sijaan teorian perusteella potentiaaliselta desinfektioaineelta myös talousvedenpuhdistukseen. Opinnäytetyötä eri hapetusmenetelmien osalta talousvedelle ei ole aiemmin tehty eikä peretikkahappohapetuksesta ole laajalti aiempaa tutkimustietoa. Kokeellisen osuuden tulokset antavat uutta tietoa menetelmien soveltuvuudesta vastaaville laitoksille.

Sellutehtaan TRS-hajapäästöjen hallinta

Diplomityön tavoitteena on selvittää TRS-hajapäästöjen muodostumista sekä päästöjen määrää UPM Kymmene Oyj:n Kaukaan sellu- ja paperitehtaalla. Työssä laaditaan TRS-hajapäästöjen mittausohjelma, minkä päivitetty massa- ja paperiteollisuuden BAT-vertailuasiakirja vaatii. Mittausohjelma täydentää tehdasintegraatin ilmapäästöjen valvontaohjelmaa. Hajapäästöjen lisäksi tavoitteena on selvittää häiriötilanteiden aiheuttamia TRS-päästömääriä. Kirjallisuusosassa selvitetään hajujen muodostumista sellun ja paperin valmistuksessa ja niiden käsittelyä ympäristövaikutusten minimoimiseksi. Lisäksi esitellään mittausmenetelmiä. Kokeellisessa osassa valituista kohteista mitataan TRS-pitoisuudet ja hajukaasujen virtaama, joiden perusteella lasketaan TRS-kuormitus. Kuormitus suhteutetaan sellutonnille. Osa kohteista on hajapäästökohteita ja osa kohteita, joista hajukaasut häiriötilanteissa johdetaan käsittelemättä ulos. Tulosten perusteella TRS-hajapäästöjä muodostuu sellun valmistuksessa noin 0,04 kgS/ADt ja jätevedenkäsittelyssä, pääasiassa lietteenkäsittelyssä 0,04 kgS/ADt. Hajapäästöjä syntyy eniten kohteissa, missä keräily on toteutettu kevyemmin tai sitä ei ole. Merkittävimmät kohteet Kaukaalla ovat lietteenkäsittely, koivukuitulinja ja mäntyöljylaitos. Havulinjan ja talteenotto-osaston hajapäästöt ovat muita osastoja vähäisemmät. Yhteensä sellutehtaan ja lietteenkäsittelyn TRS-hajapäästömäärä on 0,08 kgS/ADt, mikä on BAT vaihteluvälin (0,05-0,2 kgS/ADt) sisällä. TRS-häiriöpäästöjen osuus tehtaan TRS päästöistä voi häiriötilanteiden toistuessa nousta merkittäviksi. Tähän vaikuttaa merkittävästi häiriintyvä kohde.

Kunnallisen jätevedenkäsittelyn tehostaminen membraanitekniikan avulla – esimerkkinä Savitaipaleen jätevedenpuhdistamo

Työssä tutkittiin mahdollisuutta tehostaa kunnallista jätevedenpuhdistusta membraanitekniikkaa käyttäen. Teoriaosassa perehdyttiin kunnallisen jäteveden omi-naisuuksiin ja perinteiseen puhdistusprosessiin. Tämän lisäksi membraanien yleisiä ominaisuuksia, membraanityyppien kykyä erottaa jäteveden sisältämiä yhdisteitä sekä erilaisia mahdollisuuksia membraanisuodatukselle perinteisen jäteve-denpuhdistusprosessin yhteydessä käytiin läpi. Kokeellisessa osassa keskityttiin Savitaipaleen puhdistamon puhdistetun jäteveden laadun parantamiseen membraanisuodatukseen perustuvalla jälkikäsittely-yksiköllä eli tertiäärisuodatuksella. Erilaisia paineavusteisia membraanitekniikoita (MF, UF, NF ja RO) tutkittiin jäteveden puhdistamiseksi ja erotustehokkuuden vertailemiseksi. Tavoitteena oli löytää tehokas ja käytännössä toimiva tapa poistaa fosforia ja typpeä puhdistetusta jätevedestä. Tasomaisilla membraaneilla tehdyissä suodatuksissa MF-membraanit poistivat tehokkaasti fosforia (97 – 98 %) sekä kiintoainesta (100 %) jätevedestä. RO-membraanit alensivat fosfori- (100 %) ja typpipitoisuutta (90 – 94 %) tehokkaasti, poistaen myös liuenneita orgaanisia yhdisteitä (DOC, 90 – 94 %). Mikrosuodatukseen perustuvilla onttokuitumembraaneilla saavutettiin tehokkaan fosforinpoiston lisäksi tasainen kapasiteetti suodatuksen aikaista puhdistusmene-telmää optimoimalla. Pitoisuusalenemat olivat myös erittäin korkeita fosforille (97 – 99 %), kiintoaineelle (100 %), sameudelle (96 – 99 %) sekä COD:lle (38 – 55 %). Tulosten perusteella membraanitekniikkaan perustuva onttokuitusuodatus olisi tehokas ja toimiva jälkikäsittelyprosessi fosforinpoistoon ja jäteveden laadun pa-rantamiseen. Typen poistamiseen parhaiten toimi RO-membraani.

Formation of nitrates in water in presence of formate and oxalate treated with pulsed corona discharge (PCD)

Tavallisten hapetusmenetelmien sijasta kehittyneitä hapetusmenetelmiä (AOP) on kehitetty yhä enemmän, jotta hapetusprosessista tulisi kannattavampi, tehokkaampi, ympäristöystävällisempi ja sitä voitaisiin hyödyntää laajalti eri paikoissa. Uusi teknologia, joka käyttää otsonia ja hydroksyyliradikaalia sähköimpulssien kanssa, on yksi mahdollinen tehokkaampi vedenkäsittelymentelmä. Kyseistä menetelmää kutsutaa pulsed corona discharge (PCD) -menetelmäksi, joka käyttää prosessissa muodostuvia otsonia ja hydroksyyliradikaalia hapettavina tekijöinä. Tässä työssä tutkittiin nitraatin muodostumista vedessä, kun vettä käsiteltiin PCD-laitteessa ja, kun oksalaatti- ja formaatti-ioneja oli sekoittuneina veteen. Nitraatteja muodostuu PCD–laitteessa veteen, kun ilman typpi reagoi hapettimina toimivien otsonin ja hydroksyyliradikaalin kanssa. Aiemmissa tutkimuksissa nitraatin muodostumisen on todistettu parantuvan, kun karboksyylihapot muurahais- ja oksaalihappo ovat sekoittuneina veteen. Tässä tutkimuksessa tarkoituksena oli tutkia, miten formaatti- ja oksalaatti-ionien, joiden pitoisuudet olivat 0 ppm, 50 ppm ja 100 ppm, läsnäolo vedessä vaikuttaa nitraatin muodostumiseen. PCD-kokeista saadut näytteet analysoitiin ionikromatografilla. Kyseisessä tutkimuksessa nitraatin muodostuminen oli samansuuruista jokaisessa kokeessa hapetusajan kasvaessa samalla, kun otettujen näytteiden pH-arvot laskivat. Tuloksena voitiin pitää sitä, ettei formaatti- tai oksalaatti-ioneilla ollut vaikutusta nitraatti-ionien muodostumiseen.