Recent applications of downflow hanging sponge technology for decentralized wastewater treatment

A transition from conventional centralized to hybrid decentralized systems has been increasingly advised recently due to their capability to enhance the resilience and sustainability of urban water supply systems. Reusing treated wastewater for non-potable purposes is a promising opportunity toward the aforementioned resolutions. In this study, we present two optimization models for integrating reusing systems into existing sewerage systems to bridge the supply–demand gap in an existing water supply system. In Model-1, the supply–demand gap is bridged by introducing on-site graywater treatment and reuse, and in Model-2, the gap is bridged by decentralized wastewater treatment and reuse. The applicability of the proposed models is evaluated using two test cases: one a proof-of-concept hypothetical network and the other a near realistic network based on the sewerage network in Chennai, India. The results show that the proposed models outperform the existing approaches by achieving more than a 20% reduction in the cost of procuring water and more than a 36% reduction in the demand for freshwater through the implementation of local on-site graywater reuse for both test cases. These numbers are about 12% and 34% respectively for the implementation of decentralized wastewater treatment and reuse.

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Woven-Fiber Microfiltration (WFMF) and Ultraviolet Light Emitting Diodes (UV LEDs) for Treating Wastewater and Septic Tank Effluent

Water ◽

10.3390/w13111564 ◽

2021 ◽

Vol 13 (11) ◽

pp. 1564

Author(s):

Sara Beck ◽

Poonyanooch Suwan ◽

Thusitha Rathnayeke ◽

Thi Nguyen ◽

Victor Huanambal-Sovero ◽

...

Keyword(s):

Wastewater Treatment ◽

Light Emitting Diodes ◽

Domestic Wastewater ◽

Septic Tank ◽

Uv Disinfection ◽

Small Community ◽

Photochemical Process ◽

Light Emitting ◽

Decentralized Wastewater Treatment ◽

Septic Tank Effluent

Decentralized wastewater treatment systems enable wastewater to be treated at the source for cleaner discharge into the environment, protecting public health while allowing for reuse for agricultural and other purposes. This study, conducted in Thailand, investigated a decentralized wastewater treatment system incorporating a physical and photochemical process. Domestic wastewater from a university campus and conventional septic tank effluent from a small community were filtered through a woven-fiber microfiltration (WFMF) membrane as pretreatment for ultraviolet (UV) disinfection. In domestic wastewater, WFMF reduced TSS (by 79.8%), turbidity (76.5%), COD (38.5%), and NO3 (41.4%), meeting Thailand irrigation standards for every parameter except BOD. In septic tank effluent, it did not meet Thailand irrigation standards, but reduced TSS (by 77.9%), COD (37.6%), and TKN (13.5%). Bacteria (total coliform and Escherichia coli) and viruses (MS2 bacteriophage) passing through the membrane were disinfected by flow-through UV reactors containing either a low-pressure mercury lamp or light-emitting diodes (LEDs) emitting an average peak wavelength of 276 nm. Despite challenging and variable water quality conditions (2% < UVT < 88%), disinfection was predictable across water types and flow rates for both UV sources using combined variable modeling, which enabled us to estimate log inactivation of other microorganisms. Following UV disinfection, wastewater quality met the WHO standards for unrestricted irrigation.

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Gravity-Driven Membrane Reactor for Decentralized Wastewater Treatment: Effect of Reactor Configuration and Cleaning Protocol

Membranes ◽

10.3390/membranes11060388 ◽

2021 ◽

Vol 11 (6) ◽

pp. 388

Author(s):

Ihtisham Ul Haq Shami ◽

Bing Wu

Keyword(s):

Wastewater Treatment ◽

Municipal Wastewater ◽

Economic Feasibility ◽

Reactor Configuration ◽

Membrane Performance ◽

Decentralized Wastewater Treatment ◽

Water Head ◽

Cake Layer ◽

Gravity Driven ◽

Cleaning Protocol

In this study, three gravity-driven membrane (GDM) reactors with flat sheet membrane modules and various biocarriers (synthetic fibers, lava stones, and sands) were operated for municipal wastewater treatment. The effects of water head, periodically cleaning protocol, and operation temperature on the GDM reactor performance were illustrated in terms of membrane performance and water quality. The results indicated that: (1) the cake layer fouling was predominant (>~85%), regardless of reactor configuration and operation conditions; (2) under lower water head, variable water head benefited in achieving higher permeate fluxes due to effective relaxation of the compacted cake layers; (3) the short-term chemical cleaning (30–60 min per 3–4 days) improved membrane performance, especially when additional physical shear force was implemented; (4) the lower temperature had negligible effect on the GDM reactors packed with Icelandic lava stones and sands. Furthermore, the wastewater treatment costs of the three GDM reactors were estimated, ranging between 0.31 and 0.37 EUR/m3, which was greatly lower than that of conventional membrane bioreactors under lower population scenarios. This sheds light on the technical and economic feasibility of biocarrier-facilitated GDM systems for decentralized wastewater treatment in Iceland.

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Performance and Cost Analysis of Decentralized Wastewater Treatment Plants in Northern India: Case Study

Journal of Water Resources Planning and Management ◽

10.1061/(asce)wr.1943-5452.0000886 ◽

2018 ◽

Vol 144 (3) ◽

pp. 05017024 ◽

Cited By ~ 9

Author(s):

Nitin Kumar Singh ◽

Absar Ahmad Kazmi

Keyword(s):

Wastewater Treatment ◽

Cost Analysis ◽

Wastewater Treatment Plants ◽

Decentralized Wastewater Treatment ◽

Northern India

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History and Current Situation of Night Soil Treatment Systems and Decentralized Wastewater Treatment Systems in Japan

Water Practice & Technology ◽

10.2166/wpt.2010.096 ◽

2010 ◽

Vol 5 (4) ◽

Cited By ~ 6

Author(s):

X.M. Yang ◽

A. Morita ◽

I. Nakano ◽

Y. Kushida ◽

H. Ogawa

Keyword(s):

Wastewater Treatment ◽

Rural Areas ◽

Urban Areas ◽

Domestic Wastewater ◽

Soil Treatment ◽

Decentralized System ◽

Decentralized Wastewater Treatment ◽

Rapid Economic Growth ◽

Unique System ◽

Wastewater Treatment Systems

In Japan, night soil, or black water, was formerly used as fertilizer for agriculture. However, during the rapid economic growth that took place after 1960, chemical fertilizers began to be adopted for agriculture and night soil was almost abandoned. How to treat the excess of night soil then became a big challenge to tackle. From that time a variety of night soil treatment technologies have been developed and the Japanese government has actively promoted the construction of night soil treatment facilities all over the country. As measures for domestic wastewater treatment, sewerage systems were spread in high-density urban areas, while a decentralized system called johkasou was diffused in rural areas with low population density. Johkasou is a unique system that was devised in Japan and mainly treats domestic wastewater on-site. Night soil treatment systems and decentralized wastewater treatment systems used in Japan are introduced in this paper, in the hope that the experience acquired in Japan will contribute to improve the sanitation conditions in other countries.

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