Two-step granular activated carbon filtration in drinking water treatment

In the treatment of Finnish surface waters, the main objective is to reduce natural organic matter (NOM) before the water is disinfected. In many treatment plants, granular activated carbon (GAC) filtration is applied for the enhanced removal of NOM after conventional treatment. The aim of this study was to assess the performance of two-step GAC filtration in NOM removal and to determine its effects on the water quality in the distribution system. Furthermore, the optimal operation conditions of the existing process scheme at Helsinki Water's treatment plant after installing two-step GAC filtration and UV disinfection was evaluated. The study revealed that the major factors influencing the effective NOM removal in GAC filtration are the choice of GAC type and the frequency of regeneration. Other factors, such as empty bed contact time and biological degradation rate, were of minor importance. However, even the fully exhausted "old" GAC effectively decreased the assimilable organic carbon (AOC) and the regrowth of heterotrophic bacteria in the distribution system. The most interesting finding of the study was that introducing GAC filtration and UV disinfection increased the nitrification in the chloraminated distribution system. Introducing GAC filtration is a challenge for the more efficient use of the existing treatment process. Although optimal ozonation probably provided the highest biological activity in the following exhausted GAC filters, alone it does not justify the use of ozone. After installing GAC filtration and UV disinfection, the role of ozone is rather to provide an additional barrier against unexpected changes in the source water quality.reviewe

Decreased natural organic matter in water distribution decreases nitrite formation in non-disinfected conditions, via enhanced nitrite oxidation

Nitrite in drinking water is a potentially harmful substance for humans, and controlling nitrite formation in drinking water distribution systems (DWDSs) is highly important. The effect of natural organic matter (NOM) on the formation of nitrite in simulated distribution systems was studied. The objective was to inspect how a reduced NOM concentration affected nitrite development via nitrification, separated from the effects of disinfection. We observed that nitrite formation was noticeably sensitive to the changes in the NOM concentrations. Nitrite declined with reduced NOM (TOC 1.0 mg L-1) but increased with the normal NOM concentration of tap water (TOC 1.6 mg L-1). Ammonium oxidation was not altered by the reduced NOM, however, nitrite oxidation was enhanced significantly according to the pseudo-first order reaction rate model interpretation. The enhanced nitrite oxidation was observed with both ammonium and nitrite as the initial nitrogen source. The theoretical maximum nitrite concentrations were higher with the normal concentration of NOM than with reduced NOM. The results suggest that the role of nitrite oxidation may be quite important in nitrite formation in DWDSs and worth further studies. As a practical result, our study supported enhanced NOM removal in non-disinfected DWDSs.Maa- ja vesitekniikan tuki ry. 33297 35211 39066

Jätevesien fosfori hyötykäyttöön – teknologioita ja ohjauskeinoja

Fosfori on tärkeä ravinne, jonka louhittavat varannot ovat rajalliset. Jätevesien fosforivirrat ovat pienempiä kuin esimerkiksi lannassa, mutta ne ovat keskittyneisyytensä vuoksi kiinnostavia fosforin kierrätyksen näkökulmasta. Jäteveden sisältämän fosforin kierrättämiseksi on olemassa erilaisia teknisiä ratkaisuja – fosfori kiertää olemassa olevilla lietteenkäsittelymenetelmillä lietteen mukana tai se voidaan ottaa talteen eri osista jätevesi- ja lieteprosessia. Fosforin talteenottomenetelmistä osa sopisi Suomen oloihin kohtuullisilla muutoksilla nykyiseen infrastruktuuriin ja prosesseihin. Osa menetelmistä taas vaatisi suuria muutoksia. Tällä hetkellä mikään menetelmä ei ole vielä täysin kilpailukykyinen kustannuksiltaan, ja meille niistä parhaiten soveltuvat ovat vielä varsin kehittymättömiä. Jäteveden sisältämän fosforin kierrätykseen kannustavia ohjauskeinoja on eri Euroopan maissa käytössä varsin niukasti. Lainsäädännöllisten ohjauskeinojen nouseva ilmiö on jäteveden sisältämän fosforin talteenottovelvoite, joka on jo käytössä Sveitsissä ja Saksassa.Talteenotetun fosforin käyttö on kuitenkin vielä ratkaisematta. Fosforin kierrätyksen taloudellisia ohjauskeinoja on käytössä hyvin vähän. Informaatio- ohjauksesta hyvä esimerkki on Ruotsin jätevesilietteen sertifiointijärjestelmä. Alankomaiden fosforin arvoketjua koskeva vapaaehtoinen sopimus on kannustava esimerkki alan omasta toiminnasta kierrätetyn fosforin käytön edistämiseksi. Jäteveden fosforin kierrätyksen edistämiseksi tarvitaan useiden erilaisten ohjauskeinojen yhdistelmää eri tavoitteita ja kehityskaaren eri vaiheita varten. Kansallinen vuoropuhelu luo yhteisymmärrystä suunnasta ja hyväksyntää harkittaville ohjauskeinoille sekä kasvattaa luottamusta eri toimijoiden välillä. Julkishallinnon on syytä neuvotella lannoitevalmistealan kanssa vapaaehtoinen sopimus kierrätysravinteiden käytön edistämiseksi. Uusien ratkaisujen kehittämiseen ja käyttöönottoon tarvitaan julkista rahoitusta, joka kohdennetaan vaikuttavasti. Kierrätyslannoitteille tarvitaan kansallinen laatujärjestelmä takaamaan tuotteiden puhtaus ja turvallisuus. Muiden toimenpiteiden toteuduttua on syytä harkita kierrätysravinteiden sekoitevelvoitetta, joka takaisi lannoitteisiin vaiheittain kasvavan osuuden kierrätysravinteita. Tietopohjan vahvistaminen ja toimenpiteiden kohdentaminen edellyttävät myös lisää tutkimust

Inactivation of simulated aquaculture stream bacteria at low temperature using advanced UVA- and solar-based oxidation methods

In this work the effect of water temperature (6 +/- 1 degrees C and 22 +/- 1 degrees C) on inactivation of bacteria (104 -106 CFU mL-1; Pseudomonas spp., Aeromonas spp. and Enterobacter spp.) in simulated aquaculture streams (SAS) using UVA based advanced oxidation processes (AOP) (H2O2-assisted UVA; photocatalysis; H2O2-assisted photocatalysis) and solar driven AOPs (H2O2-assisted solar disinfection, SODIS) was studied. Efficiency at 22 degrees C in terms of inactivation rate was higher using H2O2-assisted photocatalysis (H2O2/UVA-TiO2/polysiloxane) > H2O2-assisted UVA disinfection (UVA/H2O2 - 10 mg L-1) > photocatalysis (UVA-TiO2/polysiloxane) > UVA disinfection. At low temperature (6 degrees C) the inactivation rate increased with SODIS/H2O2 > SODIS > H2O2assisted UVA disinfection (UVA/H2O2 - 10 mg L-1) > H2O2-assisted photocatalysis (H2O2/UVA-TiO2/polysiloxane) > photocatalysis (UVA-TiO2/polysiloxane). The main results indicate that the inactivation rates increased when hydrogen peroxide (10 mg L-1) was used during H2O2-assisted UVA disinfection and photocatalysis. In addition, exposure of SAS to hydrogen peroxide for 24 h (in absence of light) at room temperature decreased the subsequent exposure UVA irradiation dose by almost four times. Drastic increase of inactivation rate was observed at low water temperature (6 +/- 1 degrees C) when UVA- and solarbased AOPs were employed compared to 22 +/- 1 degrees C. The treatment with SODIS proved to be more effective in Finland than in Spain. The effect of the low temperature (6 +/- 1 degrees C) was proposed as a critical factor during UVA disinfection (UVA/H2O2 and photocatalysis) that can increase the disinfection rate constant (kmax) by 1.3-5.2 times, leading to a reduction of the treatment costs ( euro m-3) by 1.3-3.3 times. The mechanism of observed enhanced disinfection at low water temperature (6 +/- 1 degrees C) when natural solar light and UVA are employed as irradiation sources for UVA/H2O2 and photocatalytic bacteria inactivation was proposed. No regrowth was observed in case of H2O2-assisted AOPs.This work was supported by a national research project (SUNRAS PROJECT, Project AGL2016-80507-R) funded by Ministerio de Economia y Competitividad (Plan Nacional de I + D + i (2013-2016). The research was also supported by a PIF contract (UCA/REC01VI/2017) funded by Vicerrectorado de Investigacion of Universidad de Cadiz. D. Sc. Juan Jose Rueda-Marquez is grateful for financial support from Academy of Finland within the project '' Combination of Advanced Oxidation Processes and Photobiotreatment for Sustainable Resource Recovery and Wastewater Reuse'' (application number 322339). T. Homola acknowledges financial support by Czech Science Foundation project 19-14770Y and project LM2018097 funded by the Ministry of Education, Youth and Sports of the Czech Republic. Documen

Tulevaisuuden kestävä vesihuolto – ennakointi, ohjaus ja järjestäminen

Vesihuollon tulee tarjota luotettavasti riittävä määrä puhdasta talousvettä ja puhdistaa se käytön jälkeen ympäristöhaitat minimoiden. Suomessa on noin 1500 vesihuoltolaitosta. Erityisesti pienten laitosten toiminnan laadun, resurssien ja osaamispohjan varmistamiseksi tarvitaan uusia ratkaisuja. Verkostosaneerauksesta on tulossa kaikkien vesihuoltolaitosten arkipäivää. Resurssien järkeväksi kohdentamiseksi laitokset tarvitsevat verkostoaan koskevaa systemaattisesti kerättyä tietoa, sen analysointia ja yhdistelyä. Tietojen pohjalta voidaan esimerkiksi arvioida häiriöalttiutta ja riskejä sekä ennakoida elinkaarta. Tietojen keräämisen ja hyödyntämisen käytännöt ovat vesihuoltolaitoksilla kirjavat ja puutteita on ollut myös kansallisella tasolla. Siksi verkostojen nykyistä saneeraustarvetta ei voida arvioida luotettavasti. Saneeraustarpeen arvioinnin tueksi hankkeessa on kehitetty kolmitasoinen laitoskohtaisen tiedonhallinnan tasoluokitus. Siinä kuvataan, mitä toimia kunkin tason saavuttaminen edellyttää ja millaisen verkoston hallinnan kukin taso mahdollistaa. Tiedonhallinnan perustasolla vesihuoltolaitos pystyy hallitsemaan verkosto-omaisuuttaan karkeasti koko verkoston tasolla. Tälle tasolle jokaisen laitoksen tulisi päästä. Hankkeen tuloksena esitetään etenemispolku tulevaisuuden kestävän vesihuollon varmistamiseksi. Sen varrella on asteittain tiukkenevia ohjauskeinoyhdistelmiä toteutettaviksi eri ajankohtina. Ensimmäisessä vaiheessa esitetään informaatio-ohjausta ja VEETI-järjestelmän kehittämistä sekä saneeraussuunnitelmien ja pätevyyksien vaatimista. Ne voidaan toteuttaa nykyiselläkin rakenteella, mutta ne voivat toimiessaan parantaa tilannetta. Seuraavassa vaiheessa olisi astetta tiukempi ohjaus rakennemuutokseen velvoittamalla pienet kunnat yhteistyöhön ja lopuksi hyvin tiukka lakisääteinen ohjaus isompiin yksiköihin. Jos lievemmät keinot riittävät tavoitteiden saavuttamiseksi, tiukempiin keinoihin ei tarvitse mennä

Cost–Benefit Analysis of Leakage Reduction Methods in Water Supply Networks

Reducing water loss from water supply systems is often regarded as one of the most important ways to improve the resource efficiency of water supply services. However, the costs and impacts of water loss reduction efforts need to be weighed against the benefits to define the optimal water loss target level. To this end, we conducted a cost–benefit analysis of three investment-based leakage reduction methods: district metering, pressure reduction, and pipe renovations. Furthermore, we conducted uncertainty and sensitivity analysis to determine the most relevant data for leakage analysis and policymaking on a national level. The results indicate that water loss management might not be directly cost-beneficial to utilities operating with moderate leakage levels. Neither leakage percentage nor the Infrastructure Leakage Index (ILI) were suitable for leakage target setting for the Finnish utilities. The costs of investing in district metering or renovations were the most influential factors in the sensitivity analysis, but the results showed that the estimated values were sufficiently accurate for assessing leakage policies.Peer reviewe

Comparative life cycle assessment of activated carbon production from various raw materials

Funding Information: We thank Helsinki Region Environmental Services for funding this research. Publisher Copyright: © 2022 The AuthorsActivated carbon (AC) is an effective adsorbent in water treatment but its production method has significant emissions to the environment. This study aims to quantify the environmental impacts of various AC types and determine whether raw material selection could reduce the footprint of AC. A cradle-to-gate life cycle assessment (LCA) was conducted on coal, coconut shell, wood, peat, and reactivated coal ACs. The different types of raw materials were selected to reflect typical global and local availability in the selected location. Life cycle data was collected from the Ecoinvent database, scientific literature, and an industrial producer. Using CML 2001 as a characterization method, potential environmental impacts were calculated for 12 categories. The direct emissions of AC production and electricity production were the largest contributors to environmental impacts. Coal AC had the highest impact in ten out of the twelve categories. On the other hand, reactivated coal and coconut AC had the lowest impacts in three and five categories, respectively. The comparison in carbon footprints between the AC types were found to be dependent on inclusion or exclusion of biogenic emissions: When including biogenic carbon emissions, the Global Warming Potential (GWP) of reactivated coal AC was 72–80% lower than for the virgin ACs. When biogenic carbon emissions were excluded, the GWPs of the residual biomass ACs (coconut shell and wood) were found to be about 50% lower than that of reactivated coal AC. The results demonstrate that raw material choice and production method significantly affect the environmental impact of AC. To minimize site-specific impacts of AC application, technical feasibility of AC and use phase emissions need to be assessed.Peer reviewe

Nitrogen and phosphorus harvesting from liquid waste using gas permeable hydrophobic membrane (GPHM) - NPHarvest - A Business Model study

NPHarvest is a technique developed at Aalto University to recover nutrients from liquid waste. This technique has successfully recovered the Nitrogen (N) and phosphorus (P) from different types of liquid waste at the laboratory scale. After technical success in the laboratory scale, this is upscaled to pilot-scale continuous process (100 L/hour). Besides technical study, this project also studied the market potential for the NPHarvest technique and its end products in Finland. In this study, we are developing a business model for the NPHarvest technique startup company and its potential users.  The value proposition showed how to create value for the waste using the NPHarvest technique. Several alternative business models are developed for the NPHarvest technique as well as liquid waste producing companies. This study included mainly two types of a business model; (1) capital purchase business model (the liquid waste producer company purchase and install the NPHarvest unit in their process) and the (2) service business model (the liquid waste producer company only buy the service of liquid waste treatment from NPHarvest company). The licensing business model is only for the NPHarvest startup Business Company. In order to make nutrient recovery technologies more attractive, some motivation activities need to be done from an institutional level

Tailoring metal-impregnated biochars for selective removal of natural organic matter and dissolved phosphorus from the aqueous phase

Funding Information: This work was supported by the Aalto University [Grant number D/23/00.01.02.00/2019] and Maa ja vesitekniikan tuki ry [Grant number 388823]. Publisher Copyright: © 2021 The AuthorsThis study aimed to investigate how the production process of metal impregnated biochars (MIBs) affects their selectivity in the simultaneous adsorption of organic matter and dissolved phosphorus from the aqueous phase. MIBs were produced via a two-step pyrolysis procedure including impregnation of metal oxides in the structure of the softwood-derived biochars, resulting in copper-impregnated biochar (Cu-MIB) and iron-impregnated biochar (Fe-MIB). The tailoring process was conducted by optimization of pyrolysis temperature during the biochars production stage. The MIBs were characterized via advanced characterization analyses to acquire structural, elemental, and morphological properties of the adsorbent. The surface area of MIB (99 m2/g and 92 m2/g for Cu-MIB and Fe-MIB respectively) decreased compared to pristine biochar (571 m2/g), indicating a successful impregnation of metal oxide particles within the porous carbon structure. The effect of operational parameters on adsorption as well as selectivity testswere examined in the batch mode. The optimum doses for NOM removal were 2 g/l for Fe-MIB (96%) and 0.5 g/l for Cu-MIB (87%). For phosphorus removal, optimum doses were 1 g/l for Fe-MIB (95%) and 2 g/l for Cu-MIB (93%). The lower pH values favored adsorption for both MIBs. In the binary solution of NOM and phosphorus, the NOM was selectively adsorbed by the Cu-MIB, whereas phosphorus was selectively removed by the Fe-MIB. The results provide a deeper understanding of the tailoring process of biochars for producing new biochars as selective adsorbents for specific target pollutants.Peer reviewe