Suitable treatment of source separated greywater for discharge into an Urban Environment

Abstract

It can no longer be refuted that greywater reuse is paramount to curbing the persistent global water crisis. Of the domestic wastewaters, greywater is less polluted than blackwater, but treatment is still necessary to make it safe for reuse. The most common greywater reuse application is toilet flushing. However, the use of vacuum toilets in the Oceanhamnen project, covered in this thesis, means that another greywater reuse application besides toilet flushing is required. One of the proposed greywater reuse applications is recreational purposes i.e. a water park.

NSVA and the city of Helsingborg are in the process of constructing residential houses to accommodate roughly 2000 people in the Oceanhamnen area. The houses are fitted with source separating technology. An interesting opportunity is that the greywater generated from housing units could be discharged into the surrounding urban environment. However, for greywater to be discharged into a water park, water regulations dictate that the greywater is treated to ensure a safe discharge.

This thesis study aims to recommend a suitable treatment method or a combination of treatment methods that would allow for a safe discharge of treated greywater in to the water park in the Oceanhamnen area. Selection criteria are formulated in order to narrow the scope of the literature review and site visits. A number of relevant treatment methods are found using these selection criteria. Evaluation criteria are also formulated and used to further evaluate the selected treatment
methods.

Following the selection criteria, the following treatment methods are selected; the Rotating Biological contactor (RBC), Moving Bed Biofilm Reactor (MBBR), Membrane Bioreactor (MBR) Constructed wetland and the combined aerobic biofilter & constructed wetland treatment systems. The selected treatment methods are further evaluated using the evaluation criteria. Both the MBR and MBBR systems are deemed successful for treating greywater for reuse though there is need to improve P removal abilities of each system. In line with the aim of this thesis study, the MBBR system is the preferred choice (to the MBR system) as suitable greywater treatment for urban discharge (a water park) in Oceanhamnen.

Popular Abstract

Discharging wastewater into an urban water park

Greywater – a very sustainable solution to the global water crisis! Uncertainty over water availability in 2020 is very real. Many (not only water professionals) have picked keen interest in water resources and its management to ensure sustainability of the resource for the future. Many parts of the world are already facing water shortages. It is therefore imperative to find sustainable solutions to water shortages as soon as possible to avoid catastrophes that may likely arise with water shortages. Greywater reuse is one of the most promising sustainable solutions to water shortages.

Greywater is wastewater generated from showers (personal bathing), laundry washing and kitchen sinks (dish washing). Greywater is generated on a daily basis; this means that there is always a constant supply of it. This makes greywater an area of interest due to sustainability reasons. Separation of greywater and blackwater
at the source point (source separation) means that blackwater (toilet water i.e. the most contaminated part of the domestic wastewater) is excluded, enabling the reuse of greywater after treatment.

Sweden is endowed with vast water resources. Sweden continues to venture towards sustainability and greywater reuse. Currently, there is an ongoing construction of building units equipped with source separation that is geared towards greywater reuse (as a water park) in the City of Helsingborg. The project is a collaboration between the city of Helsingborg and Nordvästra Skånes Vatten och Avlopp AB (NSVA). Once completed, the housing project (located in Oceanhamnen, Helsingborg) will encompass residential and office buildings for approximately 2 000 persons. Greywater collected from these buildings will undergo treatment before reuse in a water park in the vicinity. The thesis project task was concerned with the greywater treatment and more specifically the sort of treatment systems that can be successfully adopted to achieve the reuse objective.

Detailed literature review using a formulated selection criteria and site visits of successful pilot greywater treatment systems in Berlin, Germany and Oslo, Norway was carried out. The results obtained were further assessed using a formulated evaluation criteria before selecting the most suitable selection system. One interesting aspect of this thesis study was to draw the correct scope
for the study. For example, Sweden experiences cold winters as well as summers that are relatively hot, the scope was therefore designed in a way to ensure relevance. In this case, areas that experience cold winters and warm summers were chosen. The project is located in a city with limited space. Therefore treatment systems with small area footprint were crucial if this project is to be realized. Footprint requirements eliminated constructed wetlands as possible treatment systems for Oceanhamnen. The quality of the treated greywater (effluent) was also of major focus during the thesis study. The effluent quality was assessed against applicable regulations to Sweden such as the EU bathing water quality regulation and Swedish drinking water quality requirements. Since the reuse purpose is a water park, the EU bathing water quality regulation took precedence. However, it was good to also compare the effluent to the Swedish drinking water requirements
since there is a slight risk of water consumption especially for the playing children. Upon this assessment, the Moving Bed Biofilm Reactor (MBBR) was concluded to be the best suited treatment system for Oceanhamnen that would allow safe discharge of greywater into a water park in the city.

The results and conclusions achieved in this thesis study are first and foremost hoped to foster a successful greywater reuse on a large scale (a water park) in the city of Helsingborg – the first of its kind! Also importantly, greywater reuse is sustainable and studies (such as this thesis) on greywater reuse are important for the future. Areas such as Cape Town in South Africa and other areas experiencing water scarcity across the world, should look to greywater reuse as both an immediate and even a more long term solution to water problems. Greywater reuse is the hope for the future of water security.

• author: Arinaitwe, Evalyne Cathy
• supervisor: Åsa Davidsson
• organization: Chemical Engineering (M.Sc.Eng.)
• course: VVAM01 20172
• year: 2018
• type: H2 - Master's Degree (Two Years)
• subject: Technology and Engineering
• keywords: water engineering, environmental engineering, avloppsteknik, vattenförsörjningsteknik
• language: English
• id: 8943582
• date added to LUP: 2018-06-18 14:12:42
• date last changed: 2018-06-18 14:12:42