Treatment and potential reuse of greywater from schools: a pilot study

Abstract

This study presented performance data on a low cost and easy maintenance pilot system for on-site treatment and reuse of water collected from wash sinks and fountains, as major sources of greywater (GW) at schools. Various treatment options were studied including screening, sand filtration, chlorination, and UV disinfection operated at different flow rates. Results showed that filtration operated at low rates is very effective in total suspended solids (TSS) removal, while UV proved to be more effective than chlorination for reduction of biochemical oxygen demand (BOD), chemical oxygen demand (COD), and total coliforms. Removal efficiencies up to 63%, 30% and 20% were obtained for TSS, COD and BOD, respectively and reductions of log TC (CFU/100 ml) from 6.5 to 2 were obtained at a filtration rate of 14 m/d·m. Treated effluent satisfied WHO standards for reclaimed water reuse in landscape irrigation and toilet flushing. The filtration-UV system is robust, showing the best and most reliable performance for low and high strength GW treatment even under a 10-fold increase in flow rate. A 5 m/d pilot plant was developed for schools having 500 students and detailed cost-benefit analysis indicated a net saving value, a surplus of $1,600 per year, and pay back after 6 years and 11 months.

Removal of Volatile Solids from Greywater Using Sand Filters

“…Removal efficiency of organic compounds in this study (26.8%) was similar to that obtained by Alsulaili [45] (17%) and Moges et al [46] (20-25%), and also comparable to results obtained by Santos et al [44] in a study carried out using a filter mesh of 0.130 mm diameter (47%). COD removal efficiency was much lower than the removal efficiency obtained by other authors: Martikainen et al [18]-for conventional buried sand filters (92%), and Abdel-Shafy et al [17]-for a down-flow gravel filter (74%).…”

“…The efficiency of VS removal was comparable to that obtained by Abdel-Shafy et al [17] for a down-flow sand filter-82%. The VS removal efficiency obtained in this study was in turn much higher than results obtained by other authors: Santos et al [44] for a study carried out using filter mesh of 0.130 mm diameter (28%), by Alsulaili [45] for sand filter (10%) and obtained by Moges et al [46] (15-20%-for TSS).…”

Graywater Treatment with Two Planted Vertical Constructed Wetlands in Series: A Pilot Study

“…[3] Recycling graywater, which has become an increasingly important aspect in many countries' efforts to save potable water, will cut total wastewater handling costs by reducing wastewater loads for treatment plants and reducing water and energy usage as well its accessibility and low contaminant concentrations as compared to raw sewage. [4] Excluding blackwater, domestic GW is part of household wastewater and it almost accounts for 75% of the combined residential wastewater by volume. It can contain high-strength kitchen wastewater (high load) and it is also the drain from bathtubs, shower trays, washbasins, and washing machines (low load).…”

“…[ 3 ] Recycling graywater, which has become an increasingly important aspect in many countries' efforts to save potable water, will cut total wastewater handling costs by reducing wastewater loads for treatment plants and reducing water and energy usage as well its accessibility and low contaminant concentrations as compared to raw sewage. [ 4 ]…”

Light or Dark Greywater for Water Reuse? Economic Assessment of On-Site Greywater Treatment Systems in Rural Areas

“…Thus, they propose that the reuse of greywater should be oriented to 'light' greywater, since the costs of treatment and technological complexity would be lower. However, most of the research has been focused on the performance of treatment systems and their technical characteristics (i.e., [5,[16][17][18][19][20]), while economic aspects that are critical for long-term sustainability have been approached considering particular case studies in different countries of the world [21][22][23][24][25][26][27]. Furthermore, there are no experiments that have addressed the economic viability of 'light greywater' treatment systems, compared to 'dark greywater' treatment systems.…”