In tropical regions, where most of the developing countries are located, septic tanks and other onsite sanitation systems are the predominant form of storage and pre-treatment of excreta and wastewater, generating septage and other types of sludges. The septage is disposed of untreated, mainly due to lack of affordable treatment options. This study presents lessons that have been learned from the operation of pilot-scale constructed wetlands (CWs) for septage treatment since 1997. The experiments have been conducted by using three CW units planted with narrow-leave cattails (Typha augustifolia) and operating in a vertical-flow mode. Based on the experimental results, it can be suggested that the optimum solids loading rate be 250 kg TS/m² yr and 6-day percolate impoundment. At these operational conditions, the removal efficiencies of CW units treating septage at the range of 80–96% for COD, TS and TKN were achieved. The biosolid accumulated on the CW units to a depth of 80 cm has never been removed during 7 years of operation, but bed permeability remained unimpaired. The biosolid contains viable helminth eggs below critical limit of sludge quality standards for agricultural use. Subject to local conditions, the suggested operational criteria should be reassessed at the full-scale implementation.

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.

Wetland roof (WR) system was developed to apply for building terrace and top roof in the urbanized area of Ho Chi Minh City. This study aims to improve the green area of the city and to treat domestic wastewater through a shallow horizontal subsurface constructed wetland that is located in a household roof. The pilot-scale unit of horizontal subsurface flow WR system with Melampodium paludosum, an indigenous emerging plant in Vietnam, was experimented at the average hydraulic loading rate (HLR) of 338 m³/ha d (∼36 kg COD/ha d) corresponding to HRT of 18 h. The treatment performance was not significantly different for rainy and sunny days at various HLRs. It was observed that the average removal efficiency of COD was 77–78% or 20–28 kgCOD/ha d for both sunny and rainy days. It is apparent that nutrient removal was greatly achieved as indicated by TN removal efficiency of 88–91% or 17–20 kg TN/ha d. In addition, TP removal reached 72–78% or 1.6 kg TP/ha d for different HLRs. The treated effluent could comply with the standard limits of Vietnam national technical regulation for domestic wastewater. It was also observed that the growth rate of M. paludosum was 0.1 cm/day in length. The ratio between nitrogen uptake by plants over nitrogen removed by WR was 0.13, while the higher ratio of 0.68 was obtained for the case of phosphorus. The temperature of WR units was 4 ± 1°C lower than that on concrete floor that likely help saving energy for building cooling if applying WR on the top roof. Based on the experimental results obtained to date, the WR system would be a promising system for domestic wastewater treatment especially for urbanized city, where green area is of high demand.

In developing countries with large Millennium Development Goals (MDGs) sanitation indicator, pollutant discharge reduction function of wastewater treatment systems should be considered. In this paper, pollutant generations per capita (PGCs) and pollutant discharges per capita (PDCs) are estimated as a base dataset for wastewater management in Thailand. PDCs of black water, i.e. toilet wastewater, are found to be much smaller than PGCs of black water. However, PDCs of gray water, i.e. municipal wastewater other than toilet wastewater are large. Gray water is often discharged without treatment and contributes much to ambient water deterioration. Moreover, possible 5-day biological oxygen demand (BOD5) discharge reductions with “soft interventions”, i.e. measurements in households to reduce wastewater pollutant discharge such as using a paper filter or a plastic net in kitchen sinks and so on, are estimated as 39, 21 and 34% for BOD5, total Kjeldahl nitrogen (TKN) and phosphate (PO4-P), respectively. For the estimation, environmental accounting housekeeping (EAH) books of domestic wastewater, spreadsheets with pollutant discharges by water usages and possible effects of “soft interventions” are applied. The framework of this study with “soft intervention” effects on pollutant discharge reductions should enhance wastewater management especially in the areas under development of wastewater treatment systems.

Faecal sludge (FS) from the on-site sanitation systems is a nutrient‐rich source but can contain high concentrations of toxic metals and chemicals and infectious micro-organisms. The study employed 3 vertical-flow CW units, each with a dimension of 5×5×0.65 m (width×length×media depth) and planted with cattails (Typha augustifolia). At the solid loading rate of 250 kg total solids (TS)/m².yr and a 6-day percolate impoundment, the CW system could achieve chemical oxygen demand (COD), TS and total Kjeldahl nitrogen (TKN) removal efficiencies in the range of 80–96%. A solid layer of about 80 cm was found accumulated on the CW bed surface after operating the CW units for 7 years, but no clogging problem has been observed. The CW percolate was applied to 16 irrigation sunflower plant (Helianthus annuus) plots, each with a dimension of 4.5×4.5 m (width×length). In the study, tap water was mixed with 20%, 80% and 100% of the CW percolate at the application rate of 7.5 mm/day. Based on a 1-year data in which 3 crops of plantation were experimented, the contents of Zn, Mn and Cu in soil of the experimental plots were found to increase with increase in CW percolate ratios. In a plot with 100% of CW percolate irrigation, the maximum Zn, Mn and Cu concentrations of 5.0, 12.3 and 2.5 mg/kg, respectively, were detected in the percolate-fed soil, whereas no accumulation of heavy metals in the plant tissues (i.e. leaves, stems and flowers) of the sunflower were detected. The highest plant biomass yield and oil content of 1000 kg/ha and 35%, respectively, were obtained from the plots fed with 20% or 50% of the CW percolate.

Thirty percent of the world’s population lives in East and Southeast Asia, of which close to 60% lives in urban areas. The Global Competitiveness Report 2018 recognized that the increasing economic dynamism of the region has contributed to rapid industrialization, a rise in living standards, and a drastic reduction in extreme poverty. The report further stated that the region was one of the fastest growing regions in the world in 2017, including China’s significant contribution to the region’s rapid economic growth. Such rapid growth leads to a massive consumption of natural resources, resulting in unprecedented environmental problems such as pollution, resource depletion, and waste disposal. If one considers the urban setting to be a starting point for dealing with the water–energy–food (WEF) nexus, it offers immense challenges and opportunities for innovative solutions. Innovative approaches, both existing and new technology, are required to safeguard the most critical resources. This chapter examines approaches and technologies that can contribute to overcoming nexus challenges in East and Southeast Asia.