Knut Wichmann

Review of the technological approaches for grey water treatment and reuses

Based on literature review, a non-potable urban grey water reuse standard is proposed and the treatment alternatives and reuse scheme for grey water reuses are evaluated according to grey water characteristics and the proposed standard. The literature review shows that all types of grey water have good biodegradability. The bathroom and the laundry grey water are deficient in both nitrogen and phosphors. The kitchen grey water has a balanced COD: N: P ratio. The review also reveals that physical processes alone are not sufficient to guarantee an adequate reduction of the organics, nutrients and surfactants. The chemical processes can efficiently remove the suspended solids, organic materials and surfactants in the low strength grey water. The combination of aerobic biological process with physical filtration and disinfection is considered to be the most economical and feasible solution for grey water recycling. The MBR appears to be a very attractive solution in collective urban residential buildings.

Resources and nutrients oriented greywater treatment for non-potable reuses.

This paper evaluated the performance and suitability of a resources and nutrients oriented decentralized greywater treatment system which uses a submerged spiral wound module. This greywater treatment system is aimed at treating and recovering the resources present in the wastewater. The study revealed that the UF membrane filtration system was able to maintain a permeate flux between 6 and 10 L/m2/h. TOC can be reduced from the influent value of 161 to 28.6 mg/L in the permeate, meaning an average elimination rate of 83.4%. In addition, soluble nutrients such as ammonia and phosphorus can pass through the UF membrane and remain in the permeate. The total nitrogen and total phosphorus in the permeate were 16.7 and 6.7 mg/L respectively. The permeate was low in turbidity (below 1 NTU) and free of suspended solids and E. coli and had an excellent physical appearance. The permeate can be used in gardening and agriculture for irrigation and soil fertilization or alternatively for toilet flushing after disinfection. The retentate generated in this system can be treated with blackwater and kitchen waste in an anaerobic digester at a later stage for producing biogas or compost.

Evaluation of appropriate technologies for grey water treatments and reuses.

As water is becoming a rare resource, the onsite reuse and recycling of grey water is practiced in many countries as a sustainable solution to reduce the overall urban water demand. However, the lack of appropriate water quality standards or guidelines has hampered the appropriate grey water reuses. Based on literature review, a non-potable urban grey water treatment and reuse scheme is proposed and the treatment alternatives for grey water reuse are evaluated according to the grey water characteristics, the proposed standards and economical feasibility.

Treatment of the methanogenic landfill leachate with thin open channel reverse osmosis membrane modules

A leachate purification system, equipped with the thin open channel spiral wound modules, is studied in this paper. In Phase I, effluent from an activated sludge process followed by the flocculation/sedimentation process was fed into the landfill leachate treatment unit. After 2 wk of operation, the permeate flux dropped dramatically, from an average value of 6.5l/m(2)/h to 4.23 l/m(2)/h. The significant decline of membrane flux was likely caused by membrane fouling. In Phase II, raw leachate was fed directly into the reverse osmosis leachate treatment system. An average flux of 7.8l/m(2)/h was maintained at an initial trans-membrane pressure difference of 20 bar, which increased to 40 bar before membrane chemical cleaning. An average recovery rate of 70% was achieved. Throughout the observation in Phase II, an average reduction rate of 98.2% for the dissolved solids was obtained. The reduction rate of COD was greater than 99.5% with a constant level of the permeate COD. Chloride was eliminated by more than 99%, while over 98% of NH(4)-N was reduced. A negligible permeate flux drop was observed after cleaning the membrane effectively. The study shows that direct reverse osmosis membrane filtration with thin open channel spiral wound modules is able to achieve satisfactory results in terms of water quality, process stability and membrane flux. The obtained quality of the permeate quality in this study met the German standards for leachate discharge. At the end of each filtration cycle, the membrane was maintained through alkaline chemical cleaning in order to remove any irreversible membrane fouling. After the maintenance procedure, the membrane flux was found to recover to the initial value.

Biodegradation of NOM in Rapid Sand Filters for Removing Iron and Manganese

In order to examine the Corg flow in rapid sand filter columns for the elimination of iron and manganese, reduced groundwater was treated in a pilot plant consisting of a trickling filter column (TF I) followed by a wet type filter column (WF II) and a separate wet type filter column (WF sep). Additionally the effect of filtration on BOM was studied by measuring AOC and BDOC. The biological processes in TF I and WF sep led to an elimination of iron, ammonia, and manganese. Moreover, the filtration decreased the NOM content. 21% and 23% of the TOC were eliminated in TF I and in WF sep, respectively. WF II caused no significant Corg reduction. The calculation of the Corg flow in the filter columns showed that bacteria took part in the TOC elimination. From the TOC removed, about 24% was eliminated by metabolic activities of the bacterial population whereas 86% was adsorbed onto iron sludge. Similar results were obtained for the TF I column and for the WF sep column as well. The calculated Corg flow was confirmed by the BDOC measurements. The filtration process led to a BDOC decrease. TF I and WF sep reduced appoximately 35% of the biodegradable organic carbon. In contrast there was no significant elimination by WF II. The AOC results suggest that an AOC production and an AOC elimination process exist in rapid sand filters for groundwater treatment. In the trickling filter column significant AOC production was found, whereas in the wet type filter columns AOC elimination was predominating. Biologischer Abbau von NOM in Schnellfiltern zur Enteisenung und Entmanganung Um den Corg-Fluss in Schnellfiltern zur Enteisenung und Entmanganung zu untersuchen, wurde ein reduziertes Grundwasser in einer halbtechnischen Versuchsanlage sowohl durch Trockenfiltration (TF I) mit nachfolgender Nassfiltration (WF II) als auch durch separate Nassfiltration (WF sep) aufbereitet. Weiterhin wurde der Einfluss der Aufbereitung auf den Gehalt an biologisch abbaubaren organischen Wasserinhaltsstoffen mit Hilfe einer AOC- und einer BDOC-Methode untersucht. Die biologischen Prozesse in TF I und WF sep fuhrten zu einer Elimination von Eisen, Ammonium und Mangan. Zudem bewirkte die Filtration eine NOM-Verringerung. Der TOC des Rohwassers wurde durch TF I um 21% bzw. durch WF sep um 23% vermindert. WF II fuhrte zu keiner messbaren TOC-Abnahme. Die Bilanzierung des Corg-Flusses im Filter zeigte, dass die Filterbiozonose an der TOC-Verringerung beteiligt war. Vom eliminierten TOC-Anteil wurden sowohl in TF I als auch im WF[TH]sep ca. 24% durch die metabolische Aktivitat der Bakterienpopulation in den Filtern vermindert und ca. 86% am Eisenschlamm adsorbiert. Die Ergebnisse der Bilanzierung des Corg-Flusses wurden durch die BDOC-Bestimmungen bestatigt. Die Filtration bewirkte eine BDOC-Abnahme. Durch TF I und WF sep wurde der biologisch abbaubare organisch gebundene Kohlenstoff um etwa 35% vermindert. Im Gegensatz dazu veranderte WF II den BDOC nicht. Die AOC-Untersuchungen liesen in den Filtern zur Grundwasseraufbereitung AOC-Produktions- und AOC-Eliminationsprozesse erkennen. Der Trockenfilter fuhrte uberwiegend zur AOC-Produktion, wohingegen der AOC in den Nassfiltern vornehmlich vermindert wurde.

Treatment of Groundwater Containing Methane – Combination of the Processing Stages Desorption and Filtration

Methane is produced under anaerobic conditions by metabolic processes in microbes and can occur in waters of the types anoxic-anaerobic (RG 1/2) and anaerobic-reduced (RG 2). If the concentration of methane lies below 0.2 mg/L, then no special treatment processes are required apart from dosing of oxygen and rapid sand filtration, which are performed to remove iron, manganese, and ammonium. The research results show that a higher concentration of methane must be specially treated. From the point of view of stable deferrisation, oxidation of up to 2 mg/L is tolerable in rapid sand filtration. However, an unusual increase in regrowth potential was observed. For this reason, the oxidation of methane should be reduced to 0.5 mg/L until further experiments yield results on the microbiological stability of treated water. Rapid sand filters for nitrification and demanganisation should have a maximum methane loading of 0.2 mg/L. The experiments show that nitrification first occurs at a methane concentration below 0.1 mg/L. During the working in of demanganisation, the inlet water should be free of methane. Therefore desorption is often required. If there is less than 1 mg/L to be degassed, then desorption can be achieved with overpressure in the oxidiser without any change in the carbonate-bicarbonate equilibrium. With other systems. such as packed columns, wetted-wall columns, or percolators, carbon dioxide is removed simultancously. By means of the coefficients of similarity found, it was shown that methane and carbon dioxide desorb in different proportions depending on the system, and that the discharge of carbon dioxide can be reduced through a decrease in the air/water ratio.