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Organic amendments are used to improve soil fertility and maintain agricultural fields in a productive state. Despite these benefits, the use of organic amendments is limited in many developing countries. The overall objective of this thesis is therefore to provide a better understanding of current waste management practices in developing countries and ensure sustainable crop production via the biotransformation of urban waste into a high-quality soil amendment. First, I aimed at determining the causes for the limited use of organic amendments in small-scale urban farming systems. I interviewed 220 urban farmers in Ethiopia and found that competition for agricultural waste between fuel, feed and soil amendment is a major cause for the limited use of organic amendments. I demonstrated that allocation of agricultural waste for soil amendment is linked with farmers’ livelihood strategies. I also studied variation in compost demand among different farmer groups, and the socio-economic variables which explained these variations. Gaseous losses of ammonia and greenhouse gas (GHG) emissions occur during composting of nitrogen-rich urban waste. Several technologies could reduce these losses. However, these technologies are inadequate to fit within the broader farming systems because they are expensive. The second aim of this thesis was to develop low-cost methods to mitigate N losses and GHG emissions from composting, while retaining its fertilising value. Composting by earthworms (vermicomposting) is proposed as a low-cost strategy for minimising N losses and GHG emissions. Using a wide range of substrate qualities (C:N ratio, labile C sources) and other factors (earthworm density, amount of input, and moisture), I showed that vermicomposting reduced N losses and GHG emissions compared with traditional thermophilic composting, but the magnitude of the earthworm effect varied between substrates. Earthworms also change the quantity and composition of dissolved organic carbon during composting. Another low-cost strategy is to delay the addition of N-rich substrates during composting. I demonstrated that addition of nitrogen-rich substrate after the thermophilic phase reduced N losses. Delayed addition of N-rich substrates increased N2O emissions, but reduced CH4 emissions. Delayed addition resulted in compost that was as stable and effective at completely eradicating weed seeds as traditional composting. In conclusion, urban waste compost should be considered as alternative source for soil amendment, particularly in developing countries with competition for agricultural waste. Technologies such as vermicomposting and delayed addition of N-rich substrate are recommended to increase or maintain the nitrogen content of compost, reduce N losses and mitigate GHG emissions.

A novel treatment chain for low strength domestic sewage includes low temperature anaerobic treatment as the main process. It can improve the energy efficiency of sewage treatment compared with conventional aerobic sewage treatment. A combination of an Upflow Anaerobic Sludge Blanket reactor and a sludge digester, a UASB-digester system, was proven to be one of the successful anaerobic systems to challenge temperatures as low as 10°C and organic matter concentrations in the range of 382 and 1054 mg chemical oxygen demand (COD)/l. The UASB is operated at low sewage temperature (10°C) and high loading rate. The produced non-stabilised sludge in the UASB is recirculated over the mesophilic digester (35°C) to convert organic solids to methane gas and produce anaerobic biomass fed back into the UASB reactor, where it converts dissolved COD at the low temperature of the waste water. The effect of sludge recirculation rate and sludge transfer point on the performance of a UASB-digester treating domestic sewage at 15 ˚C was studied in this research. The results show increased total COD removal efficiency when increasing the sludge recirculation rate from 1% to 2.6% of the influent flow rate. Methane gas production increases with the sludge recirculation rate, in the range of 1 to 12.5% of the influent flow rate. A higher sludge transfer point results in an increased suspended COD removal efficiency and a higher VSS concentration of the UASB sludge bed. Co-digestion was applied for improving soluble COD removal efficiency of a UASB-digester system, operated at low temperatures and treating domestic sewage with a high dissolved/suspended COD ratio. Glucose was chosen as a model co-substrate and added to the sludge digester to produce additional methanogenic biomass, which was continuously recycled to inoculate the UASB reactor. Methane production in the UASB reactor almost doubles and soluble COD removal efficiency equals the biodegradability of the influent dissolved COD, due to a twofold increase in methanogenic capacity, when applying co-digestion 16% of influent organic loading rate. Therefore, co-digestion is a suitable approach to support a UASB-digester for treatment of low temperature domestic sewage. A pilot scale UASB-digester (130 + 50 L) was studied to treat domestic wastewater at temperatures of 10-20°C at an HRT of 6 h in the UASB reactor and 15 h in the digester. The results show a stable COD removal efficiency of 60 ± 4.6% during the operation at 12.5 to 20°C. COD removal efficiency decreases to 51.5 ± 5.5% at 10°C. The decreased COD removal efficiency is attributed to an increased influent COD load, leading to insufficient methanogenic capacity of the UASB reactor at such low temperature. Suspended COD removal efficiency was 76.0 ± 9.1% at 10-20°C. The effluent COD concentration is 90 ± 23 mg/L at temperatures between 12.5 and 20°C, while soluble COD removal efficiency fluctuates due to variation in the influent COD concentration. 80% of the influent biodegradable COD is recovered as methane gas (including dissolved methane). Low temperature (10-25°C) hydrolysis after applying a short pre-hydrolysis at 35°C was studied compared with those without the pre-hydrolysis. Batch experiments were executed using cellulose and tributyrin as model substrates for carbohydrates and lipids. Low temperature anaerobic hydrolysis rate constants increase by a factor 1.5 - 10 after applying a short anaerobic pre-hydrolysis at 35°C. The hydrolytic activity of the supernatant collected from the digestate after batch digestion of cellulose and tributyrin at 35°C was higher than that of the supernatants collected from the low temperature (≤ 25°C) digestates. The observed hydrolysis in the UASB of a UASB-digester system, treating domestic sewage at low temperatures (10-20°C) is in line with the elevated hydrolytic activity of mesophilic supernatant. Effects of temperature and temperature shocks on specific methanogenic activity (SMA), and acetate affinity of the digester sludge were studied. Digester sludge from a UASB (12.5°C)-digester (35°C) system, was fed with acetate at constant temperatures of 10-35°C and at varying temperatures from 35°C to 25, to 15 to 10°C. The results show no lag phase in methane production rate when applying temperature shocks of 35°C to 25, 15, and 10°C. The temperature dependency of the SMA of the digester sludge after the temperature shocks was similar to the one at constant temperatures. Acetate affinity of the digester sludge was high at the applied temperatures (10-35°C). Latter is consistent with the finding of no VFA in the effluent of the UASB-digester, treating low strength, and low temperature (12.5°C) domestic wastewater. The UASB-digester system to treat low strength, low temperature domestic sewage was provided with a proof-of-principle, and its essential underlying anaerobic processes were sufficiently elucidated to make the technology ready for further scaling up and demonstration in practice.

Asset management is a tool for maintaining the required level of serviceability of urban drainage systems, which are costly to construct and in some cases even more costly to replace. The required asset management effort to achieve a certain level of service is unclear due to a limited knowledge on sewer failure mechanisms and due to scarcity of information on the functioning and conditions of urban drainage systems. An important question is: what information of what quality is necessary for cost-effective sewer asset management? In The Netherlands the majority of urban drainage systems are made of concrete elements (about 72%), including nearly all main sewers> 500 mm, thus making the information on the concrete sewer pipes of significant importance. This research aims at (i) identifying the required information on the structural and hydraulic performance of the sewer pipes, (ii) quantifying the uncertainties of information and (iii) improving the quality of this information in order to further understand the changes in processes/status. Sewer failure mechanisms explain the structural and/or operational failures of sewer elements. In order to be able to identify the main processes and defects responsible for the structural and/or operational failures of sewer elements, as well as the possibility of obtaining the information about them, a HAZard and Operability (HAZOP) approach was applied. This technique was demonstrated to be applicable for analysing the information needed for sewer asset management. Structural strength and hydraulic capacity are two essential parameters in the assessment of the need for sewer rehabilitation. In sewer systems where corrosion is the dominant failure mechanism, visual inspection by closed circuit television (CCTV) and core sampling are among the methods mostly applied to assess sewer pipe condition. A study was carried out on visual inspection and drill core analysis in order to enhance a further understanding of the limitations an

Black water (toilet water) contains half the load of organic material and the major fraction of the nutrients nitrogen and phosphorus in a household and is 25 times more concentrated, when collected with a vacuum toilet, than the total wastewater stream from a Dutch household. This research focuses on the partial nitritation of anaerobically treated black water to produce an effluent suitable to feed to the anammox process. Successful partial nitritation was achieved at 34 degrees C and 25 degrees C and for a long period (almost 400 days in the second period at 25 degrees C) without strict process control a stable effluent at a ratio of 1.3 NO(2)-N/NH(4)-N was produced which is suitable to feed to the anammox process. Nitrite oxidizers were successfully outcompeted due to inhibition by free ammonia and nitrous acid and due to fluctuating conditions in SRT (1.0-17 days) and pH (from 6.3 to 7.7) in the reactor. Microbial analysis of the sludge confirmed the presence of mainly ammonium oxidizers. The emission of nitrous oxide (N(2)O) is of growing concern and it corresponded to 0.6-2.6% (average 1.9%) of the total nitrogen load.

Decentrale sanitatie als invulling van een duurzame waterketen is bedacht in Wageningen en tussen 2002 en 2005 door een aantal partijen in het noorden van Nederland ontwikkeld tot een bruikbaar concept. Het demonstratieproject DeSaH in Sneek heeft laten zien dat het toepassen van decentrale sanitatie en hergebruik veel mogelijkheden biedt en zeker ook een aantal aanknopingspunten voor verdere ontwikkelingen. De resultaten van het innovatieve concept kunnen echter nog aanzienlijk worden verbeterd. Ondergetekenden zijn na het ontwerp voor het project in Sneek het laboratorium ingedoken, om met nieuwe partijen te werken aan de verbetering van de efficiency, de energieprestatie en de marktpotentie van het concept. Het resultaat is een nieuwe zuiveringstechnologie: hogedrukgisting

Separate treatment of black (toilet) water offers the possibility to recover energy and nutrients. In this study three combinations of biological treatment and membrane filtration were compared for their biological and membrane performance and nutrient conservation: a UASB followed by effluent membrane filtration, an anaerobic MBR and an aerobic MBR. Methane production in the anaerobic systems was lower than expected. Sludge production was highest in the aerobic MBR, followed by the anaerobic MBR and the UASB-membrane system. The level of nutrient conservation in the effluent was high in all three treatment systems, which is beneficial for their recovery from the effluent. Membrane treatment guaranteed an effluent which is free of suspended and colloidal matter. However, the concentration of soluble COD in the effluent still was relatively high and this may seriously hamper subsequent nutrient recovery by physical-chemical processes. The membrane filtration behaviour of the three systems was very different, and seemed to be dominated by the concentration of colloidals in the membrane feed. In general, membrane fouling was the lowest in the aerobic MBR, followed by the membranes used for UASB effluent filtration and the anaerobic MBR.

In 2009 zijn de gemeente Bergen, HHNK en Tauw een uitgebreid onderzoek gestart naar het functioneren van 2 compacte randvoorzieningen (TAST 1 en 2) met screens en lamellen. Dit artikel beschrijft de voorzieningen en onderzoeksresultaten omtrent de behaalde rendementen en het benodigde onderhoud. Tevens wordt teruggekeken naar de 5 jaar geplande emissiemaatregelen en de daadwerkelijk behaalde emissiereductie.

The pre-treatment of domestic sewage for removal of suspended solids (SS) at a process temperature of 13 degrees C and an hydraulic retention time (HRT) of 4 h was investigated in an anaerobic filter (AF) and anaerobic hybrid (AH) reactor. The AF and the top of the AH reactor consisted of vertical sheets of reticulated polyurethane foam (RPF) with knobs. All biomass in the AF was only in attached form to avoid clogging and sludge washout. The AF reactor showed a significantly higher removal of total and suspended chemical oxygen demand (COD) than the AH reactor, respectively, 55% and 82% in the AF reactor and 34% and 53% in the AH reactor. Because the reactors were operated at a short HRT and low temperature, the hydrolysis, acidification and methanogenesis based on the influent COD were limited to, respectively, 12%, 21% and 23% for the AF reactor and 12%, 17% and 16% for the AH reactor. The excess sludge from the AH reactor was more stabilised and had a better settling capacity and dewaterability. However, the excess sludge from both the AH and AF reactors needed stabilisation. Therefore, the AF reactor is recommended for the pretreatment of domestic sewage at low temperatures.

The treatment of domestic sewage at low temperature of 13 degrees Celsius was investigated in a two-step system consisting of an anaerobic filter (AF) + an anaerobic hybrid (AH) reactor operated at different hydraulic retention times (HRTs)

Urban sanitation and solid waste sectors are under significant pressure in East Africa due to the lack of competent institutional capacity and the growth of the region’s urban population. This book presents and applies an original analytical approach to assess the existing socio-technical mixtures of waste and sanitation systems and to ensure wider access, increase flexibility and ecological sustainability. It shows how the problem is not the current diversity in waste and sanitation infrastructures and services and variety of types and scales of technology, of formal and informal sector involvement, and of management and ownership modes. The book focuses instead on the lack of an integrative approach to managing and upgrading of the various waste and sanitation configurations and services so as to ensure wider access, flexibility and sustainability for the low income populations who happen to be the main stakeholders. This approach, coined "Modernized Mixtures", serves as a nexus throughout the book. The empirical core addresses the waste and sanitation challenges and debates at each scale - from the micro-level (households) to the macro-level (international support) - and is based on the results of a five-year-long interdisciplinary, empirical research program. It assesses the socio-technical diversity in waste and sanitation and provides viable solutions to sanitation and waste management in East Africa. This book provides students, researchers and professional in environmental technology, sociology, management and urban planning with an integrated analytical perspective on centralized and decentralized waste and sanitation configurations and tools for improvement in the technology, policy and management of sanitation and solid waste sectors.

Uit onderzoek verricht in het voorjaar van 2013 blijkt, dat grote hoeveelheden glasaal zich concentreerden rond het lozingspunt van de rioolwaterzuivering in Den Oever. Het is mogelijk dat onder de geconcentreerde glasalen verhoogde sterfte plaatsvindt vanwege gerichte predatie. In een onderzoek van beperkte opzet werd in het voorjaar van 2014 onderzocht of de rwzi-uitlaat in Den Oever als knelpunt voor de glasaalintrek geldt. Het onderzoek werd uitgevoerd door monitoring van met kleurstof gemerkte glasalen, waarnemingen met een akoestische onderwatercamera (DIDSON) en maagonderzoek van lokaal aanwezige potentiele predator vissen.

Uit onderzoek verricht in het voorjaar van 2013 blijkt, dat grote hoeveelheden glasaal zich concentreerden rond het lozingspunt van de rioolwaterzuivering in Den Oever. Het is mogelijk dat onder de geconcentreerde glasalen verhoogde sterfte plaatsvindt vanwege gerichte predatie. In een onderzoek van beperkte opzet werd in het voorjaar van 2014 onderzocht of de rwzi-uitlaat in Den Oever als knelpunt voor de glasaalintrek geldt. Het onderzoek werd uitgevoerd door monitoring van met kleurstof gemerkte glasalen, waarnemingen met een akoestische onderwatercamera (DIDSON) en maagonderzoek van lokaal aanwezige potentiele predator vissen.

The results of research concerning the feasibility of anaerobic treatment of domestic sewage at low temperature are summarized in this article. The batch tests demonstrated a high biodegradability of domestic sewage at 20°C (74Ž Both batch and continuous experiments for the treatment of domestic sewage showed that the removal of SS prior to anaerobic treatment of domestic sewage not only provides a stable reactor performance but also improves the removal of both colloidal (CODcol) and dissolved COD (CODdis). The results of the pre-treatment of domestic sewage in an anaerobic filter (AF) and an anaerobic hybrid (AH) reactor showed that the AF reactor is an efficient process for the removal of suspended COD (CODss), viz. 82°at an HRT of 4 h and 13°C. The novel AF reactor consists of vertical sheets of reticulated polyurethane foam with knobs, where the biomass was only in attached form. For the treatment of pre-settled sewage at 13°C, the AH reactor, with granular sludge, showed a higher total COD (CODt) removal than the UASB reactor as a result of higher CODcol removal. Therefore, the performance of a two-step system, AF AH (with granular sludge) reactor, was investigated with different HRTs at 13°C. For optimization of CODss and CODdis an HRT of 4 4 h is needed, while for optimization of CODcol removal an HRT of 4 8 h is required. A CODt removal of 71 as achieved with 60␌onversion to methane from the removed CODt when the AF AH system was operated at an HRT of 4 8 h at 13°C.

The feasibility of the so-called BIOFIX-process to treat municipal wastewater was investigated in a pilot-plant. The innovative element of this process is that carrier material to which a biofilm is attached is recirculated between a sorption reactor to take up COD from the wastewater and a reactor where this COD is used for (post-) denitrification. In between the sorption and denitrification reactor the wastewater passes two subsequent reactors for removal of the remaining COD and for nitrification, respectively. The results showed that COD uptake by the biofilm in the sorption reactor with a maximum of 34% of the influent load was far below expectations and did not meet the COD requirement for denitrification (50–60% uptake). Also, 9–21% of the influent load of ammonia was taken up by the biofilm. In the denitrification reactor this ammonia was released to the bulk and in this manner discharged with the effluent without having passed the nitrification reactor. Nitrification was inhibited by the presence of high concentrations of suspended solids (50–60 mgl–1) discharged from a COD removal reactor. Together these bottle-necks caused effluent concentrations which were well above the effluent demands and it therefore can be concluded that the BIOFIX-process is not a feasible process to treat domestic wastewater.

At the high-rate anaerobic treatment of domestic sewage, both biological and physical processes play an important role. Therefore, the anaerobic biodegradability of raw, paper-filtered and membrane-filtered sewage and black water has been investigated in batch experiments. Additionally, the effect of anaerobic digestion on physical characteristics, like particle size, surface tension and zeta-potential, of the present particles is studied. The biodegradability of domestic sewage and black water at 30 degrees C is almost similar (71-74%). Moreover, a high methanogenesis of the colloidal fraction in domestic sewage (86 +/- 3%) is achieved, showing that the low removal of colloidal particles in continuous high-rate anaerobic reactors is due to low physical removal rather than biodegradability. The lowest biodegradability is demonstrated for the dissolved fraction (62%). The results show that after anaerobic digestion the average radius of particles with diameter4.4 and0.45 microns increased for domestic sewage, while it decreased for black water. Part of the surface-active components in domestic sewage is not biodegraded during anaerobic batch digestion, as indicated by the development of the surface tension. The negative zeta-potential of all particles hardly changes during digestion, showing that colloidal interactions were not affected by anaerobic digestion.

Uitleg over de pricipes van verschillende in-vitro testen gebruikt voor het bepalen van de oestrogene potentie van monsters oppervlaktewater en afvalwater, en enige resultaten voor verschillende locaties in Nederland

Het PAV heeft twee methoden onderzocht om afvalwater uit de witloftrek te zuiveren en te ontsmetten: ontsmetting met ultra violet licht + Reciclean en zuivering met een helofytenfilter. Het gezuiverde water is in beide gevallen van goede kwaliteit en kan tijdens de trek opnieuw als proceswater worden gebruikt

Om tot meer duurzame rioolwaterzuiveringsinstallaties te komen is een groot aantal zuiveringsscenario's, bestaande uit fysisch-chemische voorzuiveringsstappen gecombineerd met fysisch-chemische en/of biologische nazuiveringsstappen, vergeleken op de aspecten energiebalans, slibhoeveelheid na verwerking, chemicalienverbruik, effluentverzouting door chemicalien, ruimteverbruik en kosten

Op verschillende plaatsen in Europa worden initiatieven genomen ter ontwikkeling van een nieuwe wijze van afvalwaterinzameling, -transport en -behandeling. Deze zijn gebaseerd op scheiding van afvalwaterstromen aan de bron (in het huishouden). Het uiteindelijk doel is het ontwikkelen van een efficiënter systeem voor de afvalwaterketen. Het alternatief moet voldoen aan de doelen en randvoorwaarden van het huidige systeem, terwijl het tegelijkertijd oplossingen genereert voor huidige knelpunten. In opdracht van STOWA is, begeleid door een breed samengestelde begeleidingscommissie, een overzicht gemaakt van de stand van zaken. Welke mogelijkheden bieden de verschillende concepten bij de actuele aandachtspunten in de (afval)waterketen in Nederland?

In 2009 zijn de gemeente Bergen, HHNK en Tauw een uitgebreid onderzoek gestart naar het functioneren van 2 compacte randvoorzieningen (TAST 1 en 2) met screens en lamellen. Dit artikel beschrijft de voorzieningen en onderzoeksresultaten omtrent de behaalde rendementen en het benodigde onderhoud. Tevens wordt teruggekeken naar de 5 jaar geplande emissiemaatregelen en de daadwerkelijk behaalde emissiereductie.

Onderhoud en aanleg van riolering kostte Nederland het afgelopen jaar ruim één miljard euro. Stichting RIONED schat dat de kosten in 2004 met 15 tot 20 procent zullen stijgen. Ongeveer eenderde van de kosten is het gevolg van inflatie; tweederde van het totale bedrag moet worden besteed aan rioolstelsels die aan vervanging en verbetering toe zijn. De levensduur van de rioolstelsels die direct na de Tweede Wereldoorlog aangelegd zijn, is namelijk verstreken en in veel stelsels is sprake van grote problemen met verstoppingen en lekkage, wat onder andere grondwatervervuiling tot gevolg heeft

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Op drie proefbedrijven is gekeken naar de kwaliteit van het drinkwater, wanneer voorspoelwater wordt vervoederd. Ook is gelet op de vervuiling van leidingen en het vrijkomen van stank.

Onderzoeksresultaten uit Nederland van IMAG-DLO

Numerous types of organic environmental pollutants are encountered in forest industry effluents which potentially could inhibit consortia of anaerobic bacteria. The purpose of this study was to collect anaerobic bioassay data from the literature to better estimate the impact of these pollutants on anaerobic wastewater treatment systems. The most important methanogenic inhibitors in forest industry wastewaters are wood resin, chlorophenols and tannins. These compounds account for toxicity in alkaline pulping liquors, bleaching effluents and debarking wastewaters, respectively. Adaptation to chlorophenol toxicity can be expected since they are eventually degraded in anaerobic systems. Wood resin compounds, on the other hand, are not biodegraded anaerobically and therefore their toxicity is persistent. Toxicity in forest industry wastewaters does not necessarily preclude anaerobic treatment. A variety of techniques can be employed to diminish inhibition, such as dilution and detoxification treatments. | Numerous types of organic environmental pollutants are encountered in forest industry effluents which potentially could inhibit consortia of anaerobic bacteria. The purpose of this study was to collect anaerobic bioassay data from the literature to better estimate the impact of these pollutants on anaerobic wastewater treatment systems. The most important methanogenic inhibitors in forest industry wastewaters are wood resin, chlorophenols and tannins. These compounds account for toxicity in alkaline pulping liquors, bleaching effluents and debarking wastewaters, respectively. Adaptation to chlorophenol toxicity can be expected since they are eventually degraded in anaerobic systems. Wood resin compounds, on the other hand, are not biodegraded anaerobically and therefore their toxicity is persistent. Toxicity in forest industry wastewaters does not necessarily preclude anaerobic treatment. A variety of techniques can be employed to diminish inhibition, such as dilution and detoxification treatments.

Bij een goed aangelegde installatie en een juist uitgevoerde reiniging lijkt beperkte tweede reiniging mogelijk, maar kan zelfs dan op een enkel bedrijf toch voor problemen zorgen.