VOL 45; NUMBER 18; 2011
A full scale worm reactor for efficient sludge reduction by predation in a wastewater treatment plant.
Tamis, J.; van Schouwenburg, G.; Kleerebezem, R.; van Loosdrecht, M. C.
Sludge predation can be an effective solution to reduce sludge production at a wastewater treatment plant. Oligochaete worms are the natural consumers of biomass in benthic layers in ecosystems. In this study the results of secondary sludge degradation by the aquatic Oligochaete worm Aulophorus furcatus in a 125 m3 reactor and further sludge conversion in an anaerobic tank are presented. The system was operated over a period of 4 years at WWTP Wolvega, the Netherlands and was fed with secondary sludge from a low loaded activated sludge process. It was possible to maintain a stable and active population of the aquatic worm species A. furcatus during the full period. Under optimal conditions a sludge conversion of 150-200 kg TSS/d or 1.2-1.6 kg TSS/m3/d was established in the worm reactor. The worms grew as a biofilm on carrier material in the reactor. The surface specific conversion rate reached 140-180 g TSS/m2d and the worm biomass specific conversion rate was 0.5-1 g TSS sludge/g dry weight worms per day. The sludge reduction under optimal conditions in the worm reactor was 30-40%. The degradation by worms was an order of magnitude larger than the endogenous conversion rate of the secondary sludge. Effluent sludge from the worm reactor was stored in an anaerobic tank where methanogenic processes became apparent. It appeared that besides reducing the sludge amount, the worms’ activity increased anaerobic digestibility, allowing for future optimisation of the total system by maximising sludge reduction and methane formation. In the whole system it was possible to reduce the amount of sludge by at least 65% on TSS basis. This is a much better total conversion than reported for anaerobic biodegradability of secondary sludge of 20-30% efficiency in terms of TSS reduction.
Conditioning of wastewater sludge using freezing and thawing: Role of curing.
Hu, K.; Jiang, J. Q.; Zhao, Q. L.; Lee, D. J.; Wang, K.; Qiu, W.
Freeze/thaw (F/T) treatment is an efficient pre-treatment process for biological sludges. When bulk sludge was frozen, tiny unfrozen regimes in the ice matrix were continuously dehydrated by surrounding ice fronts, termed as the “curing stage”. This work demonstrated that the F/T treatment could not only enhance sludge dewaterability, but also solubilize organic matters from sludge matrix. Most enhancement of sludge dewaterability was achieved during bulk freezing stage, with the waste activated sludge more readily dewatered than the mixed sludges after treatment. Conversely, the freezing stage released only limited quantities of organic matters to liquid. Conversely, the curing contributed mostly on chemical oxygen demand (COD) solubilization and NH3-N release. The crystallization of intra-aggregate moisture was claimed to damage cell membranes so to release intracellular substances to surroundings. The F/T treatment with sufficient curing is advised to effectively condition biological sludge as the feedstock of the following anaerobic digestion process.
Bacterial, viral and turbidity removal by intermittent slow sand filtration for household use in developing countries: Experimental investigation and modeling.
Jenkins, M. W.; Tiwari, S. K.; Darby, J.
A two-factor three-block experimental design was developed to permit rigorous evaluation and modeling of the main effects and interactions of sand size (d10 of 0.17 and 0.52mm) and hydraulic head (10, 20, and 30cm) on removal of fecal coliform (FC) bacteria, MS2 bacteriophage virus, and turbidity, under two batch operating modes (`long’ and `short’) in intermittent slow sand filters (ISSFs). Long operation involved an overnight pause time between feeding of two successive 20L batches (16h average batch residence time (RT)). Short operation involved no pause between two 20L batch feeds (5h average batch RT). Conditions tested were representative of those encountered in developing country field settings. Over a ten week period, the 18 experimental filters were fed river water augmented with wastewater (influent turbidity of 5.4-58.6 NTU) and maintained with the wet harrowing method. Linear mixed modeling allowed systematic estimates of the independent marginal effects of each independent variable on each performance outcome of interest while controlling for the effects of variations in a batch’s actual residence time, days since maintenance, and influent turbidity. This is the first study in which simultaneous measurement of bacteria, viruses and turbidity removal at the batch level over an extended duration has been undertaken with a large number of replicate units to permit rigorous modeling of ISSF performance variability within and across a range of likely filter design configurations and operating conditions. On average, the experimental filters removed 1.40log fecal coliform CFU (SD 0.40log, N=249), 0.54log MS2 PFU (SD 0.42log, N=245) and 89.0 percent turbidity (SD 6.9 percent, N=263). Effluent turbidity averaged 1.24 NTU (SD 0.53 NTU, N=263) and always remained below 3 NTU. Under the best performing design configuration and operating mode (fine sand, 10cm head, long operation, initial HLR of 0.01-0.03m/h), mean 1.82log removal of bacteria (98.5%) and mean 0.94log removal of MS2 viruses (88.5%) were achieved. Results point to new recommendations regarding filter design, manufacture, and operation for implementing ISSFs in local settings in developing countries. Sand size emerged as a critical design factor on performance. A single layer of river sand used in this investigation demonstrated removals comparable to those reported for 2 layers of crushed sand. Pause time and increased residence time each emerged as highly beneficial for improving removal performance on all four outcomes. A relatively large and significant negative effect of influent turbidity on MS2 viral removal in the ISSF was measured in parallel with a much smaller weaker positive effect of influent turbidity on FC bacterial removal. Disturbance of the schmutzdecke by wet harrowing showed no effect on virus removal and a modest reductive effect on the bacterial and turbidity removal as measured 7 days or more after the disturbance. For existing coarse sand ISSFs, this research indicates that a reduction in batch feed volume, effectively reducing the operating head and increasing the pore:batch volume ratio, could improve their removal performance by increasing batch residence time.
WASTE MANAGEMENT AND RESEARCH
VOL 29; ISSU 10; 2011
Cities as development drivers: from waste problems to energy recovery and climate change mitigation.
Johnson, B.H.; Poulsen, T.G.; Hansen, J.A.; Lehmann, M.
Life cycle assessment of a household solid waste source separation programme: a Swedish case study.
Bernstad, A.; la Cour Jansen, J.; Aspegren, H.
Injuries among solid waste collectors in the private versus public sectors.
Bunn, T.L.; Slavova, S.; Tang, M.
Community level composting in a developing country: case study of KIWODET, Tanzania.
Oberlin, A.S.; Szanto, G.L.
WATER SCIENCE AND TECHNOLOGY -WATER SUPPLY-
VOL 11; NUMB 4; 2011
A survey of ancient Minoan water technologies.
Gorokhovich, Y.; Mays, L.; Ullmann, L.
Deterioration in water quality from supply chain to household and appropriate storage in the context of intermittent water supplies.
Elala, D.; Labhasetwar, P.; Tyrrel, S.F.
Joint water supply projects in rural Cameroon: partnership or profiteering? Lessons from the Mautu-Cameroon Development Corporation (CDC) project.
Folifac, F.; Gaskin, S.
Biological aspects of slow sand filtration: past, present and future.
Haig, S.J.; Collins, G.; Davies, R.L.; Dorea, C.C.; Quince, C.
DEVELOPMENT AND CHANGE -THE HAGUE THEN LONDON- VOL 42; NUMBER 5 (2011) pp. 1153-1178
The Politics of Assessment: Water and Sanitation MDGs in the Middle East
Zawahri, N.; Sowers, J.; Weinthal, E.
Abstract The Middle East and North Africa (MENA) is generally considered to be making adequate progress towards meeting Target 10 of the Millennium Development Goals (MDGs), which calls for halving the proportion of the population with inadequate access to drinking water and sanitation. Progress towards achieving Target 10 is evaluated by the Joint Monitoring Programme (JMP), run by UNICEF and WHO. This article shows that the assessment methodologies employed by the JMP significantly overstate coverage rates in the drinking water and sanitation sectors, by overlooking and -not counting- problems of access, affordability, quality of service and pollution. The authors show that states in MENA often fail to provide safe drinking water and adequate sanitation services, particularly in densely populated informal settlements, and that many centralized water and sanitation infrastructures contribute to water pollution and contamination. Despite the glaring gap between the MDG statistics and the evidence available from national and local reports, exclusionary political regimes in the region have had few incentives to adopt more accurate assessments and improve the quality of service. While international organizations have proposed some reforms, they too lack incentives to employ adequate measures that gauge access, quality and affordability of drinking water and sanitation services.
WATER SCIENCE AND TECHNOLOGY
VOL 64; NUMB 8; 2011
Distribution and removal efficiency of heavy metals in two constructed wetlands treating landfill leachate.
Wojciechowska, E.; Waara, S.
A novel integrated assessment methodology of urban water reuse.
Listowski, A.; Ngo, H.H.; Guo, W.S.; Vigneswaran, S.
WASTE MANAGEMENT AND RESEARCH
VOL 29; ISSU 10; SUPP; 2011
Energy and greenhouse gas balances for a solid waste incineration plant: a case study.
Brinck, K.; Poulsen, T.G.; Skov, H.
Effects of an incinerator project on a healthcare-waste management system.
Khammaneechan, P.; Okanurak, K.; Sithisarankul, P.; Tantrakarnapa, K.; Norramit, P.
From Sanitation Updates:
Somalia: sanitary pads project gives girls a boost
11th World Toilet Summit, Haikou, Hainan, China, 22-24 November 2011
Posted: 02 Nov 2011 07:59 AM PDT
Utilizing Results-Based Financing to Strengthen Sanitation Services
Posted: 31 Oct 2011 06:14 PM PDT
Cambodia: the Hands-Off Approach to Sanitation Marketing
Posted: 28 Oct 2011 07:21 AM PDT
Making the Poor Pay for Public Goods via Microfinance
Posted: 27 Oct 2011 08:59 AM PDT